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Buying Guide - American Radio History

1. Miniature Alumi Electrol 7400 TTL 74525888 50 5 55 MB 45158086 18 1M747CN 72 AN79MOS UNAJS TE 25 02025 79 74152788 54 BOCIAN 55 452080 73 748 72 AN 9MO6 63 4882 D P4130 1500 1K 225 P4311 141 25 1 67 Part Price 741528985 78 p cogN 55 25228 90 LM1458N 54 Aroma 83 II 7 eL HM P4131 1800 1K 225 Radia 1000 25 75 7400 35 174182908 90 18k 198 M 4526BC0N 101 1MI1486N 5 j 82 P4132 2200 IK 293 Pasig 1500 25 75 b 35
2. 80 Grantham a 77 141 Heath E EA DAS 6 126 Information Unlimited 58 129 Jensen T00 o9 vds 76 Listen 80 142 Electronics 7 NRI 10 13 143 Nu Tek Electronics 80 P Boards 252 0 80 Pacific Cable Co 5 133 Parts Express International 4 122 Renaissance Software 69 137 SCO 82 SkyVision Ine succo aere ER E 80 Services aa 80 144 gio b IM 78 Trans World Cable 80 138 US Cable 71 118 nC 22022220 66 Video Link Ent Inc 80 123 Viejo 69 Wisitect 202142 80 WEKA 9 n inl ln SS eee Re 2809 27 95 Counts as 2 OPTOPLECTROME THE COMPLETE 600K OF OSCILLOSCOPES 3 n 3205 24 95 Basic Electronics Course 2613P 15 95 2883P 16 95 Fd ap Repairing AUDIO EQUIPMENT nb w a mI aT T pane 3185 34 95 2867P 517 95 Counts as 2 THE ILLUSTRATED DICTIONARY OF ELECTRONICS 2900P 24 95 Counts as 2 INNOVATIVE 2826P 15 95 Solid State ELECT
3. Name NCES m Address 17 pates ity T x State Zip Phone 4 n De Signature JE Valid tor new members only Foreign appiicants will receive special ordenng instructions Canada must remit in U S currency This order subject to acceptance by the Electronics Book Club MDN 390 3241 Counts as 2 24 95 o e e e e e e e e e e e e e e e e e e e e e e e e e e e e Ld 2912 14 95 WWMWe amercanradiobislob GQOblde TROUBLESHOOTERS B amp K Precision Test Bench 41 range voltmeter Ammeter Ohmmeter Frequency counter Capacitance meter Logic probe Transistor amp diode tester Extra PRECISION HAND HELD INSTRUMENTS SCOPE em Digital Multimeter 11 function 38 ranges including Logic Level Detector Audiole and Visual Continuity Capacitance amp Conductance measurements SCOPE Hand Held 314 Digit LCR Meter Measure capacitance resistance and induction Overload protection Includes test leads test Clips 9V battery and spare fuse SCOPE 3 Digit LCD Mini Meter 05 accuracy AC DC Voltage DC current Resistance Diode test 300 hrs battery life Overload protection DC 500V large LCD display AC 350V ohms 250V DC AC Model Mode
4. broly riot cried 50 47 P6376 45 6267 022 80 741828 1 15 71 74HC354N 110 gt sA 7 7 5 W5 for 5 watt or add o oe 0 22 50 TA 1 74 253N 90 LM340T 2 87 AN7BLIO 43 Ius Hd tha Dui Ke 50 100 P6377 49 P6268 3 2 741848 345 748257N 130 74HC356N 10 M407 1 79 AN7BLI2 45 1 Part Price watt i e 7 5W5 for 7 5Q 5 wait this 15 the Digi Key 50 220 P6378 70 P6269 42 0 33 50 74185AN 337 745258 90 74HC3BSN 79 W 3p AN7BLIS 43 ADCO O3LCN 7 36 part number 50 330 P6379 79 P8270 50 0 47 50 74191N 90 545580 1681 73HC368N 7 wap IZ 100 AN78L B 43 ADCO DALCN 4 50 M Pricing 7 30 10 500 1 000 50 470 P6380 95 P6271 60 ber 74193N 90 JAS283N 162 6 I8 E masip 15 90 78120 43 ADCOSOSICN 500 MI wan 36 325 2690 10080 16200 M 50 000 P638 138 P6272 es 74184N 90 7452978 200 LM34EN 165 AN78L24 43 10 Watt 41 378 3190 118 00 21200 50 2 200 P6382 2 52 P6273 22 50 74197N 1 05 74 258 1 70 EUN 1M348N 90 AN78MOS 63 ADCOBOSCCN 4 75 4 50 3 300 P6383 3 63 a 74251N 117 748373N 1 75 es i LM349N 135 78 06 63 ADCCS16CCN18 00 5 Watt Matal Resistor Assortments 50 4 700 P8384 gt 74J65N 55 asaan 175 24463908 70 H im3sok 750 AN7BMO7 63 ADCCSI7CCN1 25 RS105 5 each of valuas 0 302 100 912 20 10 BM 637047 P6385 21 P6274 74367N 70 7453874 198 ZANEIS 1M3501 495 ANZBMDB 63 A0CCB33CCN 5 00 300 total pieces 63 10 Posao 21
5. No Missing Codes Asthe analog input is increased from 0 to 10 V the digital output is supposed to increase from 0000 0000 0000 ro 111111111111 by 1 LSBata time without skipping any codes for a 12 bit ADC with an analog input range of Oto 10V Layout Guidelines As with any high speed A D converter good circuit layout practice is essential Wire Wrap boards are not recommended due to stray pickup of the high frequency digital noise A pc board offers the best performance Digital and analog grounds should be separated even if they are ground planes instead of ground traces Don t lay digital traces adjacent to high impedance analog traces Avoid digital layouts that radiate high frequency clock signals That is don t lay out digital sig nal lines and ground returns in the shape of a loop antenna Shield the analog in put if it comes from a different printed circuit board source For the ADC shown in Fig 1 you would set up a single point ground at AGND pin 3 Tie all other analog grounds to this point Also tie the logic power supply ground but no other digi tal grounds to this point Low impe dance analog and digital power supply common returns are essential to low noise operation of the ADC Their trace widths should be as wide as possible Good power supply bypass capacitors lo cated near the ADC package insure quiet operation Place a 10 2 capacitor in par allel with a 0 01 amp F ceramic capacit
6. RED LED 1 battery is attached A ed 1 00 each 10 tor 9 00 120 Vac 60 hz 10 amp contacts 10 for 1 50 100 for 13 00 This kit includes a TIL 31B PHOTO DIODE CET UL rated Turn shaft to turn on GREEN LED 2 p c board all the eo TO 18 case with window Infrared emitting photo IL lights or other eiectrical devices 10 for 2 00 100 for 17 00 parts and instructions to make a simple flasher cir diode CAT 31 1 00 ea 10 for 59 50 Bell rings and circuit breaks after specified YELLOW CAT LED 3 A quick and easy project for anyone with basic AAA SIZE 1 50 each amount of time Ideal for any device that needs 10 tor 2 00 100 for 17 00 soldering skills CAT LEDKIT 1 75 per kk 1 2 volts 180 mAh NCB AAA AA SIZE 2 00 each NCB C DSIZE 4 50 each 1 2 volts 1200 mAh CAT NCB D XENON long flashtube with 3 1 2 red and black ieads Ideal for e ectronic flash etrobe projects CAT FLT 3 2 for 1 00 RELAYS C Blue Boy BBS1A05A10 5 6 500 ohm coil S P S T ormaily open reed relay 2 5 amp contacts contigura 10 for 10 00 5 LATCHING RELAY 170 ohm coils 1 amp TTL com patibie UL and CSA recognized 0 787 X 0 394 X 0 394 CAT LRLY 5DC 32 50 each 12 VOLT D C COIL 61 X 42 X 44 high P C mount with pins on DIP spacing 1 50 each RECHARGEABLE BATTERY PACK USED Four AA nickel cadm
7. corded messages enter leave an swer only mode rewind etc To use beeperless units you call the answering machine and let it pick up the line It is usually necessary to listen to the OGM and let the ma chine enter the ICM cycle After the beep that signals the record incom ing message cycle you enter the ac cess code from the keypad of the call ing telephone You then use the key pad to key in the access code which may be one two or three digits de pending on the particular machine When entering the code each key must be pressed for about 2 seconds to obviate the possibility of a casual caller accidentally gaining access to your recorded messages When the machine accepts the ac cess code it will stop rewind and play back any recorded messages Al ternatively the machine may await another code to use one of the ma chine s other remote functions e Extension Pick Up This is a func tion of the Call Screening capability that automatically stops and resets the machine when any extension 15 lifted Once a ringing line is an swered many machines will proceed through its cycles of outgoing and in coming messages If you decide to speak to the caller you press a STOP Or POWER button to disengage the machine manually Extension pickup detects when a local extension is lifted When it does it automatically shuts down the machine cycle and disconnects from the line to await the next caller when the user
8. Analog waveform at the ADC input Sample points oy N sample cockouses Data words stored in memory 10111001 11101100 11111111 Fig 9 An example of an analog waveform upper and its pulse equivalent and 11101100 10111001 01000000 00110111 00000000 00110111 01000000 01111111 01111111 data word codes lower after digital conversion 72 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com Say You Saw It In Modetn Electronics Filtered signal Analog signal Caller hears Hi you have reached HR gt T 21366 Digitakto analog converter oupling DAC n Switching circuit cpu umi EEE 4 2 Bow Main pP and eantral circuit Timer counter fosa 10001100 41011001 Fig 10 To generate the outgoing message a DAC the voice synthesizer converts EEPROM data into analog form reset theentire machine other ma chines the telephone line voltage can be used to maintain the memory con tents instead of a battery e Follow Up Message Although se cond messages are usually reserved for more sophisticated voice mail systems some top of the line ma chines may support a brief second or follow up message after the caller has stopped speaking Such a mes sage might be Thank you for call ing I ll get back to you very soon
9. and renames those that are frequently used with a code that s shorter than its ASCII equivalent Compressed data is then sent over the phone line at a speed of 9 600 bps At the receiving end the MNP 5 control charac ters are expanded back into their original sequence resulting in data throughput speeds up to twice the modem s data rate Of course the actual rate increase de pends on the type of data being sent Text files compress the best because they have very predictable patterns while graphics files gain the least Furthermore if you use MNP 5 to compress a file that has al ready been compressed by another meth od you actually ose data throughput because the modem wastes time looking for patterns that no longer exist Model 9632VP Features While the Racal Vadic Model 9632VP isn t unique in its support for V 32 proto col or MNP 5 data compression nearly all 9 600 bps modems support both its price is At 1 195 list the Model 9632VP is one of the lowest cost V 32 modems available But low price doesn t mean that this modem is shy on features In fact just the opposite is the case Racal Vadic 9632V P Modem Facts Maximum data rate Supported data rates V 32 V 22 Bell 212 Bell 103 Data compression 19 200 bps with MNP 5 data compression 9 600 4 800 bps 2 400 bps 1 200 bps 300 bps MNP 5 Error correction Command languages PC interface Weight Power Warranty List price Manufactu
10. vo T E E ada d TE ve fae ded Fig 2 Prototype of project was built on perforated hoard using point to point wiring The circuitry is housed inside a standard instrument enclosure possible Make certain in both cases that you properly orient all diodes and electrolytic capacitors and prop erly base any integrated bridge recti fier assemblies used and the three voltage regulators Mount a heat sink on the tabs of voltage regulators and 2 Do not plug 4 and C5 in their sockets These ICs are to be installed only after you have conducted initial voltage checks and are certain that the circuitry is correctly wired POSITIVE and NEGATIVE controls R5 and R72 inthe basic power supply section mount off the board as does power transformer 77 Trimmer controls R9 and 0 mount on the metering circuit board while 72 can mount on or off the board depend ing on its size and weight Once the two circuit board assem blies have been wired temporarily set them aside Now machine the en closure The type and size of enclo sure you use will depend on how you configure your Power Supply The circuit board assemblies should require very little room inside the enclosure The power trans 28 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com former s will have a significant ef fect on enclosure size as will the amount of front panel space re quired fo
11. YOUR ONE STOP SOURCE OF ELECTRONICS INFORMATION 1CD 08559 MARCH 1990 2 50 CANADA 3 50 ELECTRONICS FREIE oi EA A Sey eS roe ER Em THE MAGAZINE FOR ELECTRONICS amp COMPUTER ENTHUSIASTS Alse Featured Dual Polarity Power Supp y p 24 BCD to Hex Conver er Display 38 8559 03 Prus Forrest Mims Experiments With an rf Spectrum Analyzer Probe Evaluating the Racal Vadic B dget High Speed Modem Winter 1989 COMDEX Report New Analog to Digital Converter Chips Latest Technical Books amp Literature M 20 M m t E ii UEM Lj jg ear m asl PELO cm BECEWER IC RZDOD d SEL M MODE MENORY Tas SET SET RESET Ct em TOO FM rar rt tt ot tt E 200DOEHEU so E T e en emt Do cte TIEREN DE mas FROM ICOM RECEIVERS ICOMS IC R71A and IC R7000 are the professional s choice for receiving inter national broadcasts aircraft marine business emergency services television and government bands These people demand the finest in communications and so do you ICOM puts the world at your fingertips with the IC R7000 25 2000MHz and IC R71A 0 1 30MHz commercial quality scanning receivers Incomparable Frequency Control Both the IC R71A and IC R7000 feature direct freq
12. Articles Ads amp Classifieds Also 40 s amp 50 s Radios Ham Equip Early TV Books amp more Free 20 word ad each month 6 Month Trial 11 1 Yr 20 30 1st Class A R C P O Box 802 L2 Carlisle MA 01741 makes and models of cable equipment shipped within 24 hrs Quantity discounts For free catalog send S A S E to 1 Cable Mate Inc 214 Main St Algonquin IL 60102 C O D orders accepted CALL FOR PHICES TODAY SENER 056582121 No Illinois orders WW Hours 8 00 am 5 00 pm central time CABLE T V CONVERTERS Jerrold Oak Scientific Atlantic Zenith amp many others New MTS stereo add on mute amp volume Ideal for 400 amp 450 owners A 1 800 826 7623 d B amp BINC 4030 Beau D Rue Drive Eagan MN 55122 SURVEILLANCE TELEPHONE This i a normal functioning telephone EXCEPT it has a secret built in monito Only YOU can call and monitor all conversations using a secret code and never be detected Range Unlimited 175 00 6 month Warranty Phone Tap Catalog 3 00 LISTEN ELECTRONICS 603 Elgin Muskogee OK 74401 1 800 633 TAPS CABLE CONVERTERS IN STOCK Sto f Jerrold Tocom Pioneer Scientific Atlanta Zenith Oak Hamlin Eagle and others Call or write for FREE CATALOG Mon Fri 10 to 6 Eastern Time VIDEO LINK Enterprises Inc 520 Glenbrook Rd Suite 202 Stamford CT 06906 Orders 800 622 9
13. ER RR NN RN NO CONT D UNT UN S 7 A PNEU CON I cr t m miim rmt nd ELECTRONICS TEE B E F Fig 3 Spectrum Probe oscilloscope displays showing A simuitaneous 27 and 49 MHz CB transmitter carrier signals B two closely spaced signals of a cordless telephone system C broad spectrum noise produced by dc motor D expanded view of index marker and received local AM radio station E highly expanded view of index marker generated by Spectrum Probe and F ex panded portion of trace showing signal from AM radio broadcast band stations view of just the index marker and its ac companying side lobes An expanded view of the signals from several AM radio stations is shown in Fig 3 F The apparent fuzziness of these signals is a direct result of the fact that they are amplitude modulated and bounced up and down during exposure of the oscilloscope camera interest ing experiment is to tune a radio to a sta tion that the Spectrum Probe clearly shows on the screen of the oscilloscope You can watch the crest of the wave bounce up and down in direct proportion to the audio signal When the audio sig nal is momentarily quiet the displayed wave will settle down Miniature Part 15 Vhf Transmitter During the many hours I ve spent design ing and testing miniature transmitters l ve often longed for an r f analyzer Therefore one of the most interesting
14. message the Control Circuit is sig naled to stop the OGM cycle and be gin the ICM cycle Since the OGM tape plays until the conductive strip is sensed an outgoing message can be of any duration up to the time length of the tape on which it 15 recorded Common OGM tape lengths are 30 60 and 90 seconds Another method of controlling the OGM cycleisthe recording of a series of control tones at certain points on the tape The answering machine re cognizes these tones as OGM plays and controls the cycle accordingly Typically a control tone marks the beginning and end of an OGM Since control tones can be located any where on atape the OGM can be just about any length This is also the technique commonly employed in units in which a single cassette 15 used to hold both the OGM and any ICMs Presence of the OGM control tones allows an answering machine to know where the OGM ends and to begin the ICM sequence The tone before the beginning of the OGM al lows the machine to position itself at the beginning of the OGM once again as it resets for the next call e Incoming Message When the out going message is finished the Con trol Circuit turns off the OGM play mechanism and switches in the ICM record mechanism Fig 3 The tele phone Coupling Circuit switches the telephone line to the ICM play head as well as the speaker The Control Circuit startsthe tape motor and gen erates a short tone the start record ing tone or
15. 10 50 74368N 70 7454029 4 BO ZAHCSS3N 98 E LM358 51 AN2BMDS 63 ADC 001643200 M R5205 4 each of values 1 02 109 9 831 30 pt P 26 P6277 150 754508 70 7454738 71MC534N 88 M iusso 240 AN78MIO 3 ADC S CCN 8 25 354 ps x pen ig 50 ao Santegan 150 ae 63 AnD sont 88 4 each ot values 100 10919 25 213 2 PANASONIC V SERIES L 1 53 ADO 384 total peces 63 22 P6391 42 P6280 24 Stacked Metalized Film Capacitors 5 7AHCOA40N 175 ADO 701CCN 888 194090 80 375 175 IMJGIN 281 8 8 3 DACIBODLCN 1 85 88405 of values 1009 10 2 0KQ sal 563 P6392 4 P628 27 50 7ANCBBEN 86 0 28071 1 58 288 total pieces 63 47 P6393 47 P6282 20 Part Cap Volt Price P4635 0 68 50 483 75491N 100 745572 4 50 b 3 106 24 53 c P6283 53 63 100 P6384 59 No FI VAC 10 P4536 0 82 50 572 75492N 1 12 7458724 500 73HC3002N 28 E LM384N 155 AN7905 75 OACIBDBLCN 165 10 Watt Resistor Assortments 63 220 PDC P6294 7 P 75493N 1 38 401 J4HCA020N 93 AN7906 16 DACQ830LCN 6 90 P4513 001 50 1 23 4537 1050 66 74S940N 3 50 LM3BBN 1 8i R110 2 h of all 10 watt standard resistor 958 96 63 330 P6396 92 P6285 97 A PA713 001 100 1 81 7 490N 1 8 7asasin 350 1565 AN 907 DACOBS2LCN 388 values listed in the Digi Key catalog 63 470 P6397 112 62856 114 0012750 12101 00
16. ER PHREAKING UL ELECTRONIC KITS Tracking Transmit TIMATE SOFTWARE PROTECTION ters Voice Disguisers FM Bugs Phone De Many More Catalog 2 CONSUMER vices Detectors More Catalog 1 00 XAN TRONICS 2011 Crescent Alamogordo NM ELECTRONICS DI ELECTRONICS Box 25647 WW 88310 505 434 0234 descriptions orders Tempe AZ 85285 5647 TUBES New up to 90 off S A S E COMMUNICATIONS by 298 West Carmel Drive Carmel IN 46032 LISTEN to the world Huge catalog of short wave receiving equipment including radio tele LASER LISTENER II other projects Bug type and facsimile Universal Radio 1280 ging descrambling false identification infor mation Plans kits other strange stuff In OVES TRAE SISSY DOINGS Bs Reynoldsburg OH 45065 formational package 3 00 refundable DIRI SHORTWAVE ham scanner radio books JO BOND ELECTRONICS BOX 212 Catalog 1 Tiare Publications P O Box LOWELL NC 28098 493ME Lake Geneva WI 53147 PROTECT YOUR HOME AND BUSINESS MORSE Code No Problem You can in FROM ELECTRONIC EAVESDROPPING crease your speed no matter how many times AND WIRE TAPPING COMPLETE you ve failed before Results guaranteed when COUNTER MEASURES CATALOG 3 00 you follow the instructions PASS Publish REFUNDABLE DIVERSIFIED WHOLE ing s CW Mental Block Buster program helps SALE PRODUCTS BOX 127
17. Letters Modern Electronics News New Products Books amp Literature Advertisers Index Say You Saw It In Modern Electronics WWW americanradiohistorv com EDITORIAL STAFF Art Salsberg Editor in Chief Alexander W Burawa Managing Editor Dorothy Kehrwieder Production Manager Elizabeth Ryan Art Director Barbara Terzo Artist Pat Le Blanc Florence V Martin Phototypographers Hal Keith Illustrator Bruce Morgan Photographer Joe Desposito Forrest Mims III Ted Needleman Curt Phillips Contributing Editors BUSINESS STAFF Richard Ross Publisher Art Salsberg Associate Publisher Dorothy Kehrwieder General Manager Frank V Fuzia Controller Catherine Ross Circulation Director Melissa Kehrwieder Data Processing Kathleen Bell Customer Service SALES OFFICE Modern Electronics 76 North Broadway Hicksville NY 11801 516 681 2922 FAX 516 681 2926 Jonathan Kummer Advertising Manager Emily Kreutz Sales Assistant Offices 76 North Broadway Hicksville NY 11801 Tele phone 516 681 2922 FAX 516 681 2926 Modern Electronics ISSN 0748 9889 is published monthly by CQ Communications Inc Subscription prices payable in US Dollars only Domestic one year 17 97 two years 33 00 three years 48 00 Canada Mexico one year 20 00 two years 37 00 three years 54 00 For eign one year 22 00 two years 41 00 three years 60 00 Foreign Air Mail one year 75 00 t
18. RADIO IS FUN It s even more fun for begin ners now that they can oper ate voice and link computers just as soon as they obtain their Novice class license You can talk to hams all over the world when conditions per mit then switch to a repeater for local coverage perhaps using a transceiver in your car or handheld unit Your passport to ham radio adventure is TUNE IN THE WORLD WITH HAM RADIO The book tells what you need to know in orderto pass your Novice exam Two cassettes teach the code quickly and easily Enclosed is my check or money order for 19 00 plus 3 50 for shipping and handl ing or charge my VISA MasterCard Am Express Signature Acct NO a Good from Expires Name Address THE AMERICAN RADIO RELAY LEAGUE 225 MAIN ST NEWINGTON CT 06111 CIRCLE NO 124 ON FREE INFORMATION CARD C ELECTRONICS NOTEBOOK B D Fig 6 Spectrum Probe oscilloscope displays of A 84 MH signal generated by Fig 4 transmitter B multiple exposure showing signals emitted by transmitter for three dif ferent oscillator coil taps C signal from transmitter high amplitude spike at right along with local broadcast band and TV station signals and D expanded view of C Adding a short wire antenna to the Spectrum Probe greatly increased the amplitude of the displayed signal from the transmitter on the screen of the oscil loscope Figure 6 C shows the signal when th
19. _ and CD Audio Music Disk Sampler A second CD ROM comes with Small Business Consultant and Stat Pack both from Microsoft Software accessed by the III CD s hard disk includes MS DOS version that permits partitions greater than 32 MB on the hard disk GW BAS IC HOT Pop Ups utilities with notepad datebook calendar and calculator HeadStart Office Man ager with word processor spread sheet database and spelling checker Publish It desktop publishing sys tem Splash VGA graphics program for 256 colors Twist amp Shout for printing wide spreadsheets and large banners and Chessmaster 2000 chess program Other software in cludes ATI Skill Builder tutorial for mastering the computer Comput er Ease animated tutorial for color graphics Mavis Bacon Teaches Typ ing typing tutor XTree disk file management program Backup Pro for hard disk back up to floppies DS Recover and DS Optimizer for recovering erased files from the hard disk and speeding up and de frag menting hart disk files Bookmark Plus automatic file saver Above Disc EMS Emulator Ashton Tate s Framework I and Perspective 3 D Graphics 2 995 CIRCLE 52 ON FREE INFORMATION CARD pS noc DG ie EE SE EA Se ee ee 14 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com Say You Saw It In Modern Electronics ulates output voltage at the load to compensate for test lead losses Both models feature di
20. ing MNP 5 data compression allowing you to send those 1 44MB in well under 15 minutes In addition to V 32 operation the Model 9632VP can also function as a 1 200 2 400 bps or 300 baud modem for connecting with electronic bulletin boards and other low speed user devices The Model 9632VP does this by querying the responding modem as to its typeat the beginning of the session then adjusting its speed to match that of the other mo dem Which means the Model 9632VP is a One stop source for all your modem needs at standard speeds The V 32 Story Modems communicate by first generat ing and then modulating a carrier signal that is subsequently transmitted over tel ephone lines The method of doing this is identical to the way radio and TV stations send their messages over the airwaves ex cept that the frequencies are different Modems are currently restricted to the 2 700 Hz bandwidth of the Public Switched Telephone Network PSTN dial up phone channel until ISDN be comes commonplace which ranges be tween the audio frequencies of 300 Hz and 3 kHz Consequently you don t have a lot of room to work with and the carri er frequency is pretty much limited to 2 400 Hz For full duplex two way com munications you need two carriers how ever One coming and one going leaving only 1 200 Hz of bandwidth 600 baud per channel Modems overcome this inherent speed limitation by using phase shifted keyed PSK modulation
21. sumes a great deal of memory space At the end of the recording period the digitizer is disabled and the coun ter resets to be ready to play the digi tized OGM when the answering ma chine picks up on an incoming call When the machine using DROGM picks up a ringing telephone line the Control Circuit switches in a Digital to Analog Converter DAC net work The counter cycles through its sequence of EEPROM addresses The digital data words stored in the EEPROM by the recording process are now available at the EEPROM s output and coupled to the DAC s in put In turn the DAC converts the digital data back into a proportional analog signal at its output Fig 10 By stepping through each EEPROM address at the same rate at which it was recorded data entering the DAC generates an analog signal that re sembles the voice of the user The an alog low pass filter in the output cir cuit of the DAC smoothes out sud den changes in the DAC output to improve the quality of the signal Fig 11 The primary advantage of this sys tem is reliability There are no OGM motor linkages or moving parts and no OGM tape to wear or break Limited recording time is its major disadvantage A fast sampling rate consumes a great deal of memory to ensure a suitable quality of speech so OGM times are short The DROGM method is also much more complex electrically but new machines use a single digital chip with built in digi tizing circu
22. 1 50 S amp H per item except magazine Texas residents add 7 5 sales tax TO FRANKLIN BELLE PUBLISIIERS 4639 Corona Suite 12 Corpus Christi TX 78411 512 852 0446 CIRCLE 131 ON FREE INFORMATION CARD 76 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com 17 75 17 75 Filtered waveform 10111601 11101100 11111111 11101100 10111001 01111111 01000000 Digital data words Reconstructed waveform Fig 11 An analog filter at the output smoothes out the sudden changes in the DAC s converted waveform to im prove the quality of the regenerated audio signal the Date and Time Stamp feature of some machines When an incoming call is recorded the voice synthesizer announces the current date and time and records it on tape along with the ICM During playback the recorded date and time are announced after its corresponding message This feature is handy in business use when it is im portant to know the exact date and time of every call or whenever it is necessary to discriminate the date and time of messages that are col lected over a period of days or weeks This concludes Part I Next month we will finish up with select ing a location for your telephone an swering machine hints on making connections between telephone line and telephone instrument s main taining your answering machine and selecting the best model for your par ticu
23. 2 LLS1 LASER LIGHT SHOW 3 METHODS 20 00 EH1 ELECTRONIC HYPNOTISM TECHNIQUES 8 00 1 HOMING TRACKING BEEPER TRANSMITTER 44 50 LGU6K 2 5 MW HAND HELD VISIBLE LASER GUN 249 50 BTC3K 250 000 VOLT TABLE TOP TESLA COIL 249 50 10G2K RAY GUN project energy without wires 129 95 KEIK TELEKNETIC ENHANCER ELECTRIC 79 50 WPM7K 3 MILE AUTO TELEPHONE TRANSMITTER 49 50 EML1 LOWER POWERED COIL GUN LAUNCHER 8 00 2 JL3 JACOBLADDER3MODELS 10 00 S05 10 00 LEVI 10 00 uj FMVIK MILE FM VOICE TRANSMITTER 34 50 PFSTK CONTROLLED PLASMA FIRE SABER 525 50 NIG7K FLUX NEGATIVE ION 34 50 PG5K PLASMA LIGHTNING 610 49 50 LHC2K VISIBLE SIMULATED 3 COLOR LASER 44 50 5 a ASSISTANCE KITS ASSEMBLED IN OUR LABS 15710 INFINITY XMTR Listen in via phone lines 199 50 IPG70 INVIS PAIN FIELD BLAST WAVE 74 50 ITM10 100 000 VOLT INTIMIDATOR UP TO 20 599 50 TAT30 AUTO TELEPHONE RECORDING DEVICE 24 50 PSP40 PHASOR SONIC BLAST WAVE PISTOL 89 50 DNE10 ALL NEW 26 VIVID COLORED NEON STICK 74 50 LGU20 5 TO 1MW VIS RED HeNe LASER GUN 199 50 BLS10 100
24. 745113 50 6 LM32OLZ 12 50 1M3815N 2 65 0992129 338 6524 561045 each of the 73 standard 5 89 90 P201 4775 3 31 4725 54 745114 2 2 5 72 LM7BLOSAC 48 P8216 275 2012 68 63 34 6 8 25 65 7493AN 55 74 161 63 LM32012 15 72 DP8224 4 75 4 watt carbon film resistors in the 10 26 06 7495N 63 738133N 45 7aHC 167N 63 LM320MP 2 25 LM7BLI2ACZ 54 DP8226F 2 75 senes 10 12 15 18 22 etc P2013 10 6 3 32 02 74107N 63 TAST34N 163N 63 LM320MP 12 180 LMIBLISACZ 54 PB through 1 0 megohm 4365 2014 15 6 3 gt 52 9 3 ss owes umso suem fH AT m ED X 15 4121N 60 7asr3gn 85 74HCI69N 63 240 1073127 98 peggpow 6 57 f Rsz25 SetofSeachot ine 72stenderd5 9 90 P2007 17 63 85 0 1 35 7 74123N 58 748140N pg 4ML174N 58 EMS23K 8250 0 8303 44 213 1 4 watt carbon film resistors in the P201B 68 63 0 15 36 74125N 50 JAHC17SN 58 1 2 54 1 130808 180 npp3641N 188 senes 1 3 16 20 2 4 etc P2019 100 6 3 82 0 22 35 741328 75 748151N 85 aurioaN 78 iM325N 512 13600 144 ppg3p iN 325 E UL RC al ae ES 458 2451538 B5 Uw326N 600 420 T 9 0 33 35 741450 1 03 74515789 85 74HC 194N 78 k 0 8308 2 2094 220 6 3 B5 7 3 741488 110345588 82 24 195 78 LM327N 3 m 4N7805 75 gpB310N 588 1 2 Watt Resistor Assortments P2085 5063 65 0 68 35 74150N 1 58 2 749221 110 1 432907 1 AN78
25. KLEIN 302 WEST FIFTH STREET HER MANN MO 65041 MAKE OFFER ATTRACTIVE ORIENTAL LADIES seek ing correspondence marriage Professional introductions since 1984 Asian Experience Box 1214TZ Novato CA 94948 415 897 2742 MAKE 50 hr working evenings or weekends in your own electronics business Send for free facts MJOI INDUSTRY Box 531 Bronx NY 10461 USED TECHNICAL BOOKS RADIO ELECTRONICS MATH MILITARY MAGAZINES CATALOGS ETC LARGE LIST 1 00 STAMPS OK SOFTWAVE DEPT ME 1515 SASHABAW ORTON VILLE MI 48462 SURVEILLANCE Pirvacy control Debug ging Protection kits assembled Large new catalog 5 00 Tri Tron 2209F Lapalco Har vey LA 70058 SATELLITE TV SYSTEMS UPGRADES PARTS PLUS BOOKS amp TAPES INSTALLATION VIDEO 33 95 ADD 2 S H VIDEO FREE wITH SYSTEMS Catt WRITE TOOAY h 3 9 C 800 334 6455 us INSTALL UPDATE REPAIR YOURSELF 218 739 5231 MN SKYVISION 2014 COLLEGE WAY FERGUS FALLS MN 56537 Order Back Issues of ELECTRONICS Say You Saw It In Modern Electronics QUALITY PARTS DISCOUNT PRICES xFAST SHIPPING ALL ELECTRONICS CORP 12 VOLT DC MINI FAN Howard Industries 3 15 810 Operates on e m 12 Vdc 0 10 amp 1 0 watt Compact plastic housing a 2 35 square X 1 275 thick Xx 7 l Ea 9 blade fan Two 9 pigtail leads CAT CF 1
26. Q Payment enclosed C Charge my Visa MasterCard Exp Date Signature Name Address City St ZIP All orders must be signed to be processed If I elect to keep the Manual I understand I ll also receive supplements 4 to 5 times a year at 25 per page to ensure my Manual remains completely up to date I ll be billed with each separate supplement and can return them unpaid if I m not satisfied I can also cancel further supplements at any time Learn to troubleshoot and service today s computer systems as you build a fully AT compatible micro complete with meg RAM and powerful 20 hard drive Train the NRI Way and Earn Good Money Servicing Any Brand of Computer Jobs for computer service technicians will almost double in the next 10 years according to Department of Labor statistics making computer service one of the top 10 growth fields in the nation Now you can cash in on this exciting opportunity either as a full time industry technician or in a computer service business of your own once yo1 ve mastered elec tronics and computers the NRI way NRI s practical combi nation of reason why theory and hands on building skills starts you with the fundamentals of electronics then guides you through more You assemble and test sophisticated circuitry all the your computer s intelligent way up to the latest advances keyboard install the pow
27. from 0 25 to 1 Next if the Q value of the circuit or equivalent circuit is slightly greater than 1 the overshoot will be followed by a as illustrated in B Fig 5 Example of ringing reproduced square wave with rapid decay interval A as it would appear on the screen of an oscilloscope B rapidly of decay de pends on the Q value of the equivalent RLC network DTE D CRM OG ccc SSS Ee I h 48 MODERN ELECTRONICS March 1990 WWW americanracdiohistorv com Fig 6 B That is the initial single surge is followed by one recognizable half cycle of ringing Under this con dition the rise time of the waveform is also improved to some extent If the value is much greater than 1 the initial overshoot is followed by prolonged ringing as demonstrated in Fig 6 C A practical example of this condition is seen in a defective TV sweep system described as ring ing all the way through the picture Rising High Frequency Response Although an RC amplifier does not contain inductance per se the ampli fier will overshoot and ring on a square wave test if it has rising high frequency response This is exempli fied in Fig 7 In this case the ampli fier rings because the rising high fre quency response is equivalent to a basic flat amplifier plus a high frequency RLC peaking network In turn the amplifier overshoots and rings because i
28. the mo dem has taken a quantum leap forward in performance Versatility is a must with high speed modems if they re to be anything more than a luxury An important requirement is the multi speed feature supported by the Racal Vadic Model 9632VP that lets the modem operate at 1 200 and 2 400 bps for use with dial up services and oth er users who haven t upgraded to V 32 Without the ability to shift gears the user is limited to just sending files back and forth between another V 32 modem Another Model 9632VP key feature to keep in mind is MNP 4 error correction and MNP 5 data compress Both are find ing widespread use among V 32 modems and the new generation of 2 400 bps mo dems When talking to a 2 400 bps mo dem using MNP 5 data compression ac tual data throughput is at speeds up to 4 800 bps When talking to another V 32 modem using MNP 5 data compression you ll hit speeds of 19 200 bps High speed V 32 modems are likely to find wide appeal among heavy PC users because of the time and phone charges they save Desktop publishing and CAD CAM users should find V 32 s high speed ideal because of the size of the files their applications generate Financial analysis and mainframe links are also prime targets for V 32 performance Until recently though V 32 modems with list prices topping 2 000 have been out of reach for most PC users This is why the 1 195 Racal Vadic Model 9632VP under 1 000 on the streets mo dem
29. 4273 4099BCN_ 75 MM 215225 23 28304 1 122 3 8 630 26 P8201 16 M paag 15000 25 1 20 120 22071K 12 1 522 2 US 7418241N 65 7409255 6 38 45038CN 33 26227 23 283019 114 PNA24B 34 6 3 220 P6303 35 P6202 21g P449 2200025 120 121 270 1K 12861250 X059 HC 18 162 1350 7452438 66 74692846 5 38 4510BCN 80 M 2 6320 2 30 2N3020 144 4249 34 6 3 330 P6304 42 P amp 203 22M 4150 3200025 176 P4122 330 1K 1 99 M iz 000 X077 HC 18 162 1340 74152448 B5 7229277 636 451 BCN 80 BM 25527 2 50 2N3053 144 PNA250 34 6 3 470 P6305 46 P6204 23 Pa 52 1000 50 1 09 P4123 390 1 1399 M X060 HC 18 180 1500 7418245 6 7408284 5 38 4512BLN BO M 2 5322 2 30 2N310 1 0 PN4250A 40 6 3 1 000 P6306 64 P6205 38 M P4153 10050 109 41224 47K 19 Bg X061 HC 18 180 1500 7ALS2 9N 124 74C932N 1 23 4514804 108 M 2N5323 184 283108 1 0 Pha258 30 6 322 200 P6307 81 P6206 62 2200 50 108 4125 560 1K 1 89 M 25 ooo X062 E 198 15 50 74 S251N 60 740941N 198 4515808 108 MI 2N5400 31 MPS29078 3 4274 283 63 3300 P6308 95 P6207 al 09 199 8 55 55 X063 He ds 198 1650 74152538 60 74C945N 1125 a5 6BLN 83 M 255401 31 MPS2924 36 PN4275 29 6 3 4 700 P6309 1 13 P6208 101 120 2 25 5 1 1850 74526788 50 749494 11 25 4518BCN 83 3 t B MPS3392 24 PN4355 36 6 3 6 800 P6310 148 P6209 1 22 1 24 225 M 29 000 _ X06 HC18 199 16 The Digi Kev volume d
30. A radio frequency spectrum analyzer is similar in principle to an audio spectrum analyzer Both instruments provide c graphical display on which signals are plotted as a function of both frequency and amplitude Serious audiophiles find an audio spectrum analyzer indispens able for observing the nature of an audio signal and for equalizing the frequency response of a system to best match the acoustics of a particular room or auditor ium An r f spectrum analyzer is even more important since unlike audio sig nals r f signals ordinarily cannot be sensed by the human body An r f spectrum analyzer can be used to measure the absolute frequency and amplitude of a signal It can also be used to compare the relative frequencies and amplitudes of two or more signals The signal can be generated by a circuit under test or from an unknown source In any case a quick glance at the analyzer s screen will reveal if the signal has a nar row bandwidth or if it is noisy An analyzer greatly simplifies align ment of an r f source because harmonics noise and spectrum broadening are easily visible It s also a valuable tool for find ing and correcting unwanted r f leaks and signals these features and advantages can be very expensive Consider for exam ple Hewlett Packard s Model 3585 20 i i lt PE T F 2 5 y MEL Fig 1 The Spectrum Probe spectrum analyzer in operation with an osc
31. INFORMATION CARD At Em Ens See gee Tan eemper a THE ULTIMATE ELECTRONICS CATALOG 14 000 money saving electronic parts and equipment Send 3 00 a check or money order or call 1 800 543 3568 today and use your Mastercard or Visa Consolidated Electronics Incorporated 705 Watervliet Ave Dayton Ohio 45420 2599 Name Addreas City CIRCLE NO 128 ON FREE INFORMATION CARD 82 ee E a Pocket Alarm from page 52 Tide Clock from page 37 you the sign of the difference but this will be easy enough to figure out once the project is operating Then you can mark the panel accordingly For a drive frequency of 57 987 Hz adjust the setting of the potenti ometer in the slow direction for a LED blink rate of about two times per second For accuracy you could use a stopwatch to time the beat fre quency over intervals of about a min ute For a frequency of 60 1643 Hz adjust so that the LED blinks once every 6 09 seconds For frequencies close to 60 Hz the beat frequency LED can be a quite useful indicator Without a frequency counter or beat frequency indicator just set the potentiometer to about the middle of its range and hope forthe best Sever al corrections will probably be need ed over a period of many days to ac curately calibrate the Tide Clock If this is your method of calibration it helps to mark the potentiometer set ting each time
32. If the coupon is missing write to NRI School of Electronics McGraw Hill Continuing Education Center 4401 Connecticut Avenue NW Washington DC 20008 world experience you need to wor bis r with troubleshoot and service today s most widely used computer sy stems McGraw Hill Continuing No Experience Needed 4401 Connecticut New Explore the Latest NRI Builds It In Avenue NW Advances in Voice Synthesis Washington DC 20008 School of Electronics This is the kind of practical hands on Now NRI also includes innovative experience that makes you uniquely registered trademarks of hands on training in voice synthesis Internati one of today s most exciting and wide ly applied new developments in com puter technology You now train with and keep a ec full featured 8 bit D A converter that FET arcum ILE JE E CM attaches in line with your computer s parallel printer port Working with the McGraw Hill Continung Education Center 4401 Connecticut Avenue NW Washington DC 20008 Air Conditioning Heating amp Refrigeration exclusive text to speech software also FREE CATALOG ONLY 0 Telecommunications Small Engine Repair _ Computer Electronics Industrial Electronics Electrician included with your course you i O TV Video Audio Servicing C Electronic Circuit Design C Locksmithing the fascinating t
33. Industrial is a pair of low cost power supplies for bota CD ROM Based New from Headstart Technologies Great Neck NY is a CD ROM based PC that offers the user quick access to large volumes of data in teraction with other drives ability to play audio CDs with stereo sound and unlimited possibilities of inter active information combining sound graphics and text in single ap plications The 8 12 MHz 80286 HeadStart III CD has a socket for 80287 match coprocessor It features IMB of RAM expandable to 3 MB clock calendar with lithium battery back up six 8 16 bit expansion slots 256K of video RAM 101 key Jaa dude l A PS 2 style keyboard 5 25 inch 680M CD ROM drive with stereo sound 40 MB 28 ms hard disk with 1 1 interleave 1 44M 720K 3 5 inch floppy drive VGA card stereo headphones mouse 9 and 25 pin serial a parallel port bus mouse connector and game ports stereo phono jacks for CD audio and stereo mini headphone jack for play back of CD video One CD ROM supplied with the III CD has on it New Grolier Elec tronic Encyclopedia Microsoft Bookshelf with dictionary almanac manual of style thesaurus etc HeadStart CD ROM Library Disk PC Globe computerized world atlas bench use The supplies offer dual output ranges 15 volts at 2 amperes for the Model MPS60 and 30 volts at 3 amperes for the Model MPS100 Remote sensing in the MPS100 reg
34. It is not difficult to understand why an amplifier that has a very non linear phase characteristic is rapidly curved at high frequencies Envelope delay distortion also known as phase distortion is the inevitable re sult This is just another way of stat ing that the higher harmonics in the square wave are not equally delayed from one harmonic to the next in passage through the amplifier In stead the rapid curvature in the phase characteristic bunches up the high frequency harmonics with respect to time In turn the sum of the higher frequency harmonics be comes abnormal with accompanying overshoot If an amplifier has a comparatively slow rolloff characteristic in its fre quency response it will also have a comparatively linear phase charac teristic In the case of an ideal linear phase characteristic all harmonics in asquare wave will be equally delayed from one harmonic to the next and the reproduced square wave will be undistorted In practice no amplifier has an ideal phase characteristic However when reasonably slow high frequen cy rolloff is provided square wave distortion becomes negligible or at the very least tolerable It is not ordi narily feasible to display the phase characteristic of an amplifier on the screen of an oscilloscope However Say You Saw It In Modern Electronics Output voltage Frequency Maximum effective Q value NOTE Phase characteristic becomes very
35. Procomm Plus In addition to the Hayes AT command set the Model 9632VP also supports a Racal Vadic pro prietary command set called ATPlus that is asuperset of Hayes AT With ATPlus you can control modem capabilities not available in AT like manual synchron ous operation nice feature of the ATPlus command set is a user friendly interface that tells you in plain English what s happening with your connection or what the modem needs in the way of in put ATPlus commands be entered into the modem using a software package that has a script language like Procomm Plus or by typing in the commands from the keyboard while in DOS Automatic dialing of telephone num bers that contain up to 36 digits and auto log on are supported by both command sets In the AT command mode the Model 9632VP can store up to four phone numbers in nonvolatile memory In the ATPlus mode up to 15 phone numbers can be saved User Comments Installing the Racal Vadic Model 9632VP modem is about as simple as it gets Altogether there are four back panel connectors to fill three of which are signal and one for the power The connection to the PC or terminal is via a standard 25 RS 232 port Power comes from aremote supply that has two 6 foot cords emanating from its plastic 58 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com box a low voltage cable that plugs into the modem and a standard power cord that plugs into
36. SERVICE CALL TOLL FREE 1 800 729 9000 DAMARK INTERNATIONAL INC 6707 Shingle Creek Parkway Minneapolis MN 55430 Customer Service 612 566 4940 Please rush me Leading Edge Computer s 1999 each plus 39 00 s h each Item No B 1842 133967 Please rush me Hand Scanner s 99 each plus 5 00 s h each Item No B 1842 134270 Nannie Address City State Zip LJ Check MO O VISA D Master Card O Discover Card No Exp Date eee Phil pon aM Signature 1 1 1 MN res add 6 sales tax March 1990 MODERN ELECTRONICS 53 WWW americanradiohistorv com PRODUCT EVALUATION The Racal Vadic V 32 Modem High Speed Data Communication on a Budget By TJ Byers an age when you can fly from Los geles to New York in 4 hours you might reasonably ask why you should you have to wait nearly 2 hours for your 2 400 baud modem to transmit the contents of a single 1 44MB 3 5 inch floppy diskette from one PC to another answer is that you shouldn t have to wait so long and now you don t new generation of 32 modems like the Racal Vadic Mod el 9632VP solves the problem by offer ing data throughput at speeds up to 19 200 bps bits per second over stan dard telephone lines Although the V 32 standard is rated at 9 600 bps the Model 9632VP is ableto double the data rate us
37. This is a very rare feature in answer ing machines since most callers will hang up immediately after leaving their messages but it is ideal in busi ness use where an extra measure of courtesy is important Digitized Speech The techniques and components for synthesizing di gital speech have come a long way in the last few years New machines in corporate a digitizer and a memory chip to make up a DROGM Digital ly Recorded Out Going Message in stead of using an OGM tape Shown in Fig 8 is one possible ap proach for assembling a voice digi tizer recorder Pressing the OGM record button erases the existing con tents of the EEPROM Electrically for transmission over the telephone line Erasable Programmable Read Only Memory and then starts a timer that sequentially loads digital words from an Analog to Digital Converter ADC The timer circuit also sup plies an enable signal and clock pulses to the ADC When speech reaches the micro phone the analog voltage is ampli fied and sent to the input ofthe ADC where it is sampled at a very rapid rate Each sample is converted to an equivalent digital word which is taken from the output of the ADC when each conversion is complete A strobe pulse records the digital word in an EEPROM address and then advances the counter to the next EEPROM address Fig 9 There is a time limit with digital re cordings usually in the range of 30 seconds since rapid sampling con
38. a 117 volt ac power outlet The two remaining outlets are phone jacks one to connect the modem to the telephone line the other labeled TELSET to be used to connect a standard tele phone through the modem to minimize the number of phone connections in your system When you use the telset op tion a relay in the modem disconnects the handset when the modem is in service You can override the disruption using the voice data switch Basically that s all there is to installa tion If by someremote chance your com munications software program requires special hardware settings you ll have to make them from the keyboard Unfor tunately the user s manual doesn t ex plain the procedure in lay terms so the process may be confusing to some users Of the many software communications packages tested on the Model 9632VP the modem showed no hardware or soft ware problems The only quirk noted was that the speaker didn t turn off when switching from voice to data when used with Smartcom III or HyperAccess But it s not a life threatening problem If you find it bothersome there s a volume con trol within easy reach on the rear panel Conclusions There has never been a better time to buy modem than now Today s modems of fer more features and better reliability and are easier to use than modems of the Say You Saw It In Modern Electronics past With the adoption of V 32 as the in ternational 9 600 bps standard
39. americanradiohistorv com Say You Saw It In Modern Electronics standards is done with simple soft ware commands and does not require setting of switches or jumpers The MVGA 16 works with multi frequency IBM PS 2 and compatible monitors Depending on the monitor used extended resolutions of 800 by 600 pixels with 16 colors 640 by 480 pixels with 256 colors and 1 024 by 768 pixels with 16 colors can be dis played Additionally several 132 column modes can be displayed on all compatible monitors High speed Gesign is said to improve graphics drawing of the card by more than 50 over that achieved by the IBM VGA 499 with 256K of RAM 699 with 512K of RAM CIRCLE 59 ON FREE INFORMATION CARD Levered Cutting Tweezers Cutting tweezers with a lever action device are available from Aven Tools Inc Ann Arbor MI The lever is said to dramatically reduce the force required to make cuts re ducing muscle tension and thereby providing better muscle control for miniaturized work The E Z cut ting device is available on 12 differ ent cutting tweezers that have vari ous blade configurations sizes The lever can be positioned to ac commodate both right and left hand use CIRCLE 60 ON FREE INFORMATION CARD Cordless Video Light The Model V 0870 Compact One Powerlight from Ambico Norwood NJ provides 20 watts of quartz halogen illumination at a col or temperature of 3 200 degrees
40. an oscil loscope B graph of ringing frequencies FI and F2 Transient Ringing Waveforms ringing waveforms are transient in nature and eventually decay to zero However some decay slowly others rapidly This decay rate is a function of the circuit s value When is high R is small and the I2R resistivelossis correspondingly slow With reference to Fig 5 when R is comparatively large and the circuit bandwidth is large a square wave will be reproduced with overshoot and ringing evident for only brief in tervals following the leading and tralling edges of the square wave The Q value of a parallel resonant circuit or equivalent parallel reso nant circuit is equal to XL R Since XL XC at resonance the Q value of the circuit is also equal to XC R It is helpful to note that a definitive A value of circuit resistance is called the critical resistance abbreviated R This critical resistance is equal to 24 L C Under this operating condi tion the overshoot is a single surge without subsequent ringing as illus trated in Fig 6 A By way of com parison the Q value under this con dition is 1 If the Q value is reduced to 0 25 there will be no overshoot However the corner of the reproduced square wave will be substantially rounded off This is just another way of stat ing that the rise time of the waveform is considerably faster if overshoot is permitted by increasing the Q value
41. and pin 8 again not pin 7 as shown goes to ground In Fig 2 C4 should be labeled C14 and Q1 should be shown as an npn not pnp transistor Vic Richter Kerville TX Setting the Record Straight The Table of Contents in the December 1989 issue of Modern Electronics lists the wrong author for Making Printed Cir cuit Boards Without Photography This article was actually written by Jan Axelson as shown on page 16 K Furstman Astoria NY ELECTRONICS 650 CONGRESS PARK DR CENTERVILLE OH 45459 4072 A PREMIER Company SOURCE NO ME 52 March 1990 MODERN ELECTRONICS 7 WWwWwesamericanradiohistorv com MODERN ELECTRONICS NEWS PARTS DISTRIBUTOR NEWS Digi Key Corp the nationwide distributor of electronic components since 1972 added Industrial Devices products to its store of parts This rounds out the distributor s offering in neon and incandescent lamps says Stan Springsteen Digi Key s Vice President of Marketing JDR Microdevices which has an extensive catalag of microcomputer devices has started a 24 hour electronic bulletin board system BBS with on line product information tech help free software conferences and more including on line orders from JDR The BBS will also host several SIG special interest Group sub boards for Apple Amiga Atari and Commodore users plus Tech Talk and High Tech among others as well as 20 categories of software for downloading utilitie
42. are ten more chap ters Chapter 3 discusses digital receivers as they are now and what can be expected in the foreseeable future Surface mount and LSI technologies are treated in depth in the next chapter Chapter 5 deals with the art science and practice of TV servicing Here is where the test instruments specific to TV troubleshooting and repair are identified and their utilization discussed The next five chapters dissect the TV receiver devoting indi vidual chapters to mono and stereo sound tuner types luma chroma sync processing circuits power supplies and antennas transmission lines and MATV systems Projection TV and cath ode ray tubes are dealt with in Chapter 11 The book closes with a look at the near future of TV with a discussion on high defini tion television HDTV and the steps that might lead up to this ultimate goal which is expected to be the next wave in improved performance reception From the foregoing it should be obvious that this book pro vides a well rounded overview of modern TV receiving equip ment and the techniques required to service and repair it while at the same time giving an insight into where the technology began and where it is heading Excellently rendered schematics draw ings and photos are liberally distributed throughout the book to support the easy to understand text NEW LITERATURE Computers amp Electronics Catalog Jameco Electronics new 1990 catalog of compu
43. ask that they be WWW americanradiohistorv com 7 disk 1249 World 29 World map prog allows you 8 disk 20 PART TIME FROM YOUR OWN HOME Secrets Revealed NO Special Tools or Equipment Needed THE MONEY MAKING OPPORTUNITY OF THE 1990 S IF you are able to work with common small hand tools and are familiar with basic electronics i e able to use voltmeter understand DC electronics IF you possess average mechanical ability and have a VCR on which to practice and learn then we can teach YOU VCR maintenance and repair FACT up to 90 of ALL VCR malfunctions are due to simple MECHANICAL or ELECTRO MECHANICAL breakdowns FACT over 77 million VCRs in use today nationwide Average VCR needs service or repair every 12 to 18 months Viejo s 400 PAGE TRAINING MANUAL over 500 photos and illustrations and AWARD WINNING VIDEO TRAINING TAPE reveals the SECRETS of VCR mainte nance and repair real world information that is NOT available elsewhere Also includes all the info you ll need regarding the BUSINESS SIDE of running a successful service opera tion FREE INFORMATION CALL TOLL FREE 1 800 537 0589 Or write to Viejo Publications 3540 Wilshire BL STE 310 Los Angeles CA 90010 Dept ME CIRCLE NO 123 ON FREE INFORMATION CARD Renaissance Software Library TOP 20 SOFTWARE HITS 3 00 disk 2 50 disk for 10 1 disks 190 192 PC File dB top notch database
44. at a fixed rate regardless of the number of recorded messages In most such systems the LED blinks to signal the number of waiting mes sages For example a LED could blink five times to indicate five wait ing messages briefly extinguish to signal the end of the count and then continue to blink to signal the count The cycle repeats until the messages are played back at which point the circuit resets and causes the LED to remain lit continuously once again until new messages are recorded Some answering machines employ seven segment numeric displays to show the number of recorded ICMs The counters in most such machines count from 00 to 99 Seven segment LEDs and LCDs are used for this Line is idle T No connection R Panel controls PLAY REW FF MEMO N Fig 6 Buttons on an answering machine permit the incom ing message tape to be be manipulated as in any other audio Say You Saw It In Modern Electronics switching network task Upon message playback the counter resets and the display reads 00 again until new incoming mes sages are recorded Newer more expensive machines may use a built in speech synthesizer to actually announce the date and time as well as the number of re corded messages Voice synthesis may also be used to provide vocal prompts from the machine to guide the user through each operating step e Paging Automatic paging is rarely found in answering machines and the
45. ex periments I ve performed with the Spec trum Probe was evaluation of a minia ture vhf transmitter which I described in the April 1987 installment of this column Shown in Fig 4 is the schematic dia gram of the circuitry for this transmitter The transmitter can be switched on by a pressure or light sensitive switch to noti fy you when mail has been placed in your mailbox It can also be used as part of a wireless doorbell or intrusion alarm sys tem By replacing R7 with a suitable vari able resistance detector it can even be used as a telemetry transmitter that trans mits temperature light intensity or other physical analog data The transmitter depicted in Fig 4 was designed to meet the requirements of Part 15 122 of Title 47 in the Code of Federal Regulations This regulation per mits periodic low power transmission at any frequency beyond 70 MHz In the band from 70 to 130 MHz maximum field strength of the fundamental fre quency is restricted to 500 microvolts meter at a distance of 3 meters This per mits a transmission range on the order of hundreds of feet Part 15 122 permits a maximum trans mission time of 1 second and minimum interval between transmissions of 10 sec onds The silent interval must be at least 30 times the duration of the transmis sion Therefore if a pulse is transmitted once every 10 seconds its duration must not exceed 0 33 second The Fig 4 circuit transmits a 0 24 sec ond b
46. from the bat tery So if you use a heavy duty alka line battery for B you should ob tain a long life from the battery a Construction Owing to the simplicity of this proj ect in terms of component count and the fact that nothing is critical about component location and conductor runs you can build the Pocket Say You Saw It In Modern Electronics Ri R2 470K 1M PARTS LIST B1 9 volt alkaline battery 470 16 volt electrolytic capacitor ICI LMS555 timer PB1 PC mount 2 8 kHz piezoelectric buzzer Radio Shack Cat No 273 065A All resistors 4 watt 5 tolerance R1 470 000 ohms R2 1 megohm R3 1 5 megohms R4 2 2 megohms R5 22 000 ohms S1 Spst push push slide or toggle switch S2 4 position DIP switch assembly 53 momentary action spst pushbutton switch Misc Printed circuit board or perfor ated board with holes O 1 inch centers and suitable Wire Wrap or soldering hardware see text 44 x 24 x 1 plastic enclosure see text snap type connector and holder for 9 volt battery spacers lettering kit see text clear spray acrylic fast set ting epoxy cement or silicone adhe sive see text machine hardware hookup wire solder etc Fig 1 Complete schematic diagram of the project s circuitry Snooze Alarm using any traditional wiring technique that suits you If you wish you can wire the circuitry on a small pri
47. hangs up Remote Room Monitor This is a function of beeperless remote con trol that allows a user to call in and listen to any sounds in the vicinity of the answering machine via its built in speaker To use the room monitor you call the machine and enter the ac cess code The machine then waits for an additional code to select the desired function the code is usually one or two digits depending on the machine Now you enter the proper code at which point the machine connects the microphone to the line and allows you to listen to any sounds within the machine s range After a certain period of time usu ally 30 seconds the machine discon nects from the line and awaits a new function command Private Coded Messages A few an swering machines have a second OGM that can be activated by a Touch Tone code entered by the call er For example if an expected caller needs special instructions or infor mation that is not to be available on the regular OGM hecan enter a code usually two digits to initiate play back of an alternate OGM that can be left just for that particular caller Of course the caller will have to know the code in advance to reach the private message e Answer Only This mode plays back only an OGM and then hangs up It is used to provide information to a caller but not to take any mes sages This mode may be activated by beeperless remote control or by a switch on the machine itself e High S
48. in 4049 CMOS hex in verting buffer C2 wired here as astable or free running multivibra tor Clock frequency is determined by the values of R9 and Ideally operating frequency of the clock generator is calculated using the for mula f 1 2 2RC The main objec tive in selecting the values of the re sistor and capacitor was to have a digit select frequency that was high enough to obviate perceptible flicker of the lighted segments in the display The output at pin 2 of C2 goes to the input at pin 1 of counter C4 The internal counter to which pin 1 of IC4 connects operates as a BCD de cade counter The output at pin 3 of this counter furnishes the clock sig nal that is fed to pins 8 of 7415173 quad D type flip flops C6 through IC11 The output at pin 5 of JC4 goes to the pin 10 cluck enable inputs of the same ICs The output at pin 6 of C4 pro vides the clock input to pin 15 of the second counter inside this chip and the write enable WE signal to pin 2 of 74C917 display controller driver The output at pin 7 of C4 con nects to segment output enable SOE 15 of C1 The duty cycle of the pulse train fed to the C pin 15 input determines the segment on off time and subsequently the brightness of the lighted segments in the display If you wish to temporarily reduce power dissipation you can do either of two things to extinguish the dis play You can switch off the 5 volts to the entire ci
49. in the floor panel for the circuit board as sembly and power transformer and an entry hole for the ac line cord through the rear panel Determine exactly where in the top panel to make the cutout for the six decade numeric display s window and cut a suitable slot for it Then cut narrow slits through the rear wall panel near JI and J2 through which to route the two input cables Make these slits on ly wide enough to pass through the ribbon type input cables If you are using the POWER switch and fuse also drill holes in which to mount them through the front panel If you drilled the holes or cut the display slot through metal panels deburr them to remove sharp edges Then mount the power transformer in place with suitable machine hard ware sandwiching the mounting tab of a two lug terminal strip neither lug connected to the mounting tab between the nut and one tab of the transformer Connect and solder the two secondary leads of the trans former to the appropriate points in the bridge rectifier arrangement in the power supply Crimp but do not solder the pri mary leads of the power transformer to the lugs of the terminal strip If the line cord entry hole is through a me tal panel line it with a rubber grom met Pass the unfinished end of the line cord through the hole and into the enclosure Tie a strain relieving knot in it about 6 inches from the un finished end inside the enclosure Tightly twist together the fin
50. instructional help 6 days a week toll free Each CIE lesson is authored by an independent specialist backed by CIE instructors who work directly with you to answer your questions and provide technical assis tance when you need it pit ED S e C CIE World Headquarters Practical Training At Your Own Pace Through CIE you can train for your new career while you keep your pres ent job Each course allows a gener ous completion time and there are no limitations on how fast you can study Should you already have some electronics experience CIE offers several courses which start at the intermediate level State Of The Art Facilities amp Equipment In 1969 CIE pioneered the first elec tronics laboratory course and in 1984 the first Microprocessor Laboratory Today no other home study school can match CIE s state of the art equipment And all your laboratory equipment is included in your tuition cost There is no extra charge it s yours to use while you study at home and on the job after you complete your course Earn Your Degree To Become Professional In Electronics Every CIE course you take earns you credit towards the completion of your Associate in Applied Science Degree so you can work towards your degree in stages And CIE is the only school that awards you for fast study which can save you thousands of dollars in obtaining the same electronics education found in four year Bachelors Degree
51. is to build the circuit around an integrated circuit oscilla tor chip Of the oscillator chips that are commonly available the Exar XR 2206CP was chosen for this proj ect because it has the best thermal stability rated at 20 ppm C The stability of the XR 2206CP chip is more than adequate for a clock with an analog display This is because the error in reading the posi tion of the hand against the clock dial alone is much greater than the oscil lator would accumulate during weeks Of worst case operation Another advantage of the XR 2206CP shown for C2 in Fig 2 is the low additional external component count required to configure a square wave oscillator with this chip In this circuit the operating frequency of the oscillator built around 2 is de termined solely by the capacitance of C2 and series resistance of R1 and FINE ADJUST potentiometer R8 With a capacitance value of 1 mi crofarad the resistance required is 17 425 ohms A 16 000 ohm value for R1 and 2 000 ohm value for the potentiometer permits the operating frequency of the oscillator to be ad justed over a range of 55 5 to 62 5 Hz enough to allow for trimming purposes and to make up for slight discrepancies in component values The square wave output at pin 11 of IC2 is directly coupled to the input of C3 at pins 5 7 9 and 11 The un connected pins of C2 provide a sine wave output and some other func tions that are not of interest here Capacit
52. machine is not activated without gen wr mg erating a toll charge saving on the cost of expensive long distance con nect charges When the appropriate number of rings have passed the Pickup Circuit activates the main control which then switches in the Telephone Cou pling Circuit to make the connection to the line The caller hears only a click as the machine picks up Outgoing Message The Control Circuit activates the tape motor and the OGM play mechan ism which then plays the outgoing message tape The caller hears the outgoing message that is read by the OGM play head amplified and cou pled into the active telephone line by the telephone coupling circuit De pending upon the design of the parti cular machine the OGM be made to play through the speaker as well as being transmitted over the telephone lin to the caller The OGM is generally recorded on an endless cassette tape with a conductive strip that joins both ends Asthis strip passes an internal sensor at the end of the recorded outgoing Gm m BEN AURA nue RR md T x m NN L c C0 Photo shows OGM and ICM tapes inserted into a Radio Shack Realistic brand answering machine 20 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com Say You Saw It In Modern Electronics ium Lo egenum Gne
53. period of time Before calibration make sure the circuit 15 actually working by plug ging the clock motor into the ac re ceptacle on the rear panel of the en closure Then allow the circuit to sta bilize and the case to warm up by run ning the project for 20 minutes or so under load If you have a frequency counter connect it to the Tide Clock via 1 and J2 While observing the counter s display adjust the setting of the potentiometer for a precise 57 9865772 Hz output Accuracy to two or three decimal places will be quite sufficient Without a frequency counter cali bration is more difficult but still pos sible Using the panel mounted LED the output of the oscillator can be compared with the 60 Hz line fre quency The frequency of the flashes of the LED then represents the dif ference between the drive and ac line frequency This method will not tell Continued on page 82 March 1990 MODERN ELECTRONICS 37 AWW americanradiohistorv com Project BCD to Hex Converter Display Easily converts and displays binary coded decimal data in hexadecimal format By Lloyd W Redman ational Semiconductor makes an integrated circuit that offers an ideal solution to the problem of having to convert binary coded decimal BCD data into the hexadecimal format The six digit hex display controller driver 74 917 chip decodes and dis plays on separate numeric display devices 24 bits of hex data from
54. quieter than LSB This improved noise performance has immediate application in DSP digi tal signal processor processing resulting in improved signal to noise ratios Servo positioning systems also benefit from the low transition noise of the ADC 912 The fast 12 microsecond conversion time of the ADC 912 makes it well suited for data acquisition systems Also bat tery operated equipment can take advan tage of the ADC 912 s 95 mW maximum power consumption The half width 24 pin skinny DIP and 24 lead SOL packages permit production of compact portable equipment The ADC 912 s fast 90 ns access time allows direct interface with no wait states to of eight bit serial I O analog to digital converters that include on board refer ence multiplexer and track and hold functions see Fig 3 The family called the ADC08031 series features a conver sion time of 8 microseconds four times faster than National s earlier series of ADC0831 devices The new devices include the ADC 08031 ADC08032 ADC08034 and ADC 08038 which offer one two four and eight analog input channels respectively and are pin compatible upgrades for the earlier ADC0831 ADC0832 ADC0834 and ADC0838 The new components of fer high speed digital interface and on board track and hold Track and hold allows the analog input to vary during the conversion process A reference is also provided on the ADC08034 and ADC 08038 that is not available on the A
55. respectively The output of the second counter inside C4 is in verted by a second gate inside C3 and is available at pin 11 This in verted signal is fed back to master re set pin 14 of C4 The second ripple counter inside IC4 counts from 0 to 5 and resets to 0 The outputs at pins 13 11 and 10 generate the address code for inter nal registers of JC These outputs also connect to 74LS138 1 of 8 de coder 5 at pins 1 2 and 3 respec tively Though C5 is in reality a 1 of 8 decoder it is wired here as a 1 of 6 decoder BCD data is temporarily stored in IC6 through C1 before it is switched from pins 6 5 4 and 3 of these flip flops to the A B and D inputs of at pins 3 4 5 and 6 respectively Notice in the schematic that the clock enables E1 pins 9 of through wired to ground logic low When the E2 clock enables at pins 10 of C6 through 11 are low the next low to high transition of the clock signal connected to pin 7 of each of these flip flops loads the BCD data into the chips When the E2 pin is high on any flip flop the next high to low transition of the clock signal latches the BCD data in to that flip flop Outputs of through 11 op erate independently of the inputs Output enable OE2 pin 2 in all six cases is wired to ground logic low When output enable OE1 pin 1 goes low the data latched into the flip flops appears at output pins 3 4 5 an
56. s FM radio transmission band a popular rock and roll music program is the 200th station to carry CUE Paging Corp s nationwide network of FM subcarriers to its subscribers The subcarrier is the part of the FM band that transmits signals like Muzak background music weather reports and time signals The CUE pager also provides voice message service to its customers FREE SAMPLES Motorola MOS Memory Products Div announced an offer of free engineering samples of its 12 nanosecond 16K x 4 fast static random access memory FSRAM one of its newest products Each sample pack contains 8 one micron MCM 290J12 devices in the SOJ package This is a full 64K bytes of memory for use with the newest 33 MHz 32 bit systems To order the free sample pack send your business card and a brief description of your application to Motorola Semiconductor Products Literature Distribution Center P O Box 20924 Phoenix AZ 85036 0924 or call your local Motorola sales person AA SSS M c P 2 M M N U 8 MODERN ELECTRONICS March 1990 Say You Saiw It In Modern Electronics WWW americanradiohistorv com 9 Reasons you ll really enjoy The Modern Electronics Manual Look how want make your cwn printed circLits now 1 Select the board layout you 2 Place it on wp of a photo sensitive copper baseboard and expose to sun ight spotlight or i
57. sockets and com ponents If you are using a pc board they are already wired together A fairly foolproof method of wir ing any project using the point to point technique is to make up a Wir ing List that details every wire run and connection and check off each as it is made The complete Wiring List for this project is shown elsewhere in this article Carefully following each step as detailed in it should yield a working project the first time out Next using the Wiring List and an ohmmeter or audible continuity test er check all runs and connections for continuity When you obtain the proper indications in all cases as semble the power supply circuit if there is room for them you can mount the rectifier diodes two capacitors and regulator 1 12 on the circuit board assembly Do not at tempt to mount the power trans former on the board If you wish you can incorporate a POWER switch and l ampere slow blow fuse in a holder into the primary side of the power transformer in the traditional manner Select a suitable enclosure for the project It can be all plastic all metal or a combination of the two The en closure must be large enough to ac commodate the circuit board assem bly and power transformer without crowding and have sufficient front panel room for the POWER Switch and a bayonet type fuse holder if you decide to use these two components Machine the enclosure as needed That is drill mounting holes
58. switch Crimp and solder the black insulated lead of the battery snap connector to the other lug of the latter switch Checkout amp Use With the 555 timer chip still not plugged into its socket snap a fresh 9 volt battery into the connector and place the battery in its holder Con nect the common lead of a dc voltme ter or multimeter set to the dc volts function to the negative lead of the capacitor Set 7 to on Touch the hot probe of the meter to pin 8 of the IC socket and observe the reading obtained on the meter If it is not 4 9 volts power down the circuit and rectify the problem Once you are certain that the proj ect has been correctly wired turn off the power Then install the 555 timer chip in the IC socket Make certain that the timer is properly oriented in the socket and that no pins overhang the socket or fold under between IC and socket Now select the shortest duration snooze period by setting switch 1 in the switch assembly to Upon power up of the project you should immediately hear aloud beep ing from the buzzer Press and re 43 Fig 4 Faorication details for front panel of specified enclosure If you use an enclosure that has different di mensions make suitable adjust ments in machining details lease the START pushbutton switch to begin the timing interval countdown of 5 minutes At theend of the count down interval the buzzer sh
59. the screen As the active area of thesensing pad is about 7 5 by 7 5 inches this mode works well for many drawing applications The other two modes WIZ can be used in are drawing and template In drawing mode the WIZ is used with a CAD or paint program The line will follow the movement of the mouse on the pad If you place a picture on the pad and use the reticle s cross hairs to follow the lines they will be reproduced on the screen This is the same way expensive digitizing tablets work except that their tracing de vices often resemble hockey pucks rather than a mouse with a monocle By loading in a software template and placing a plastic overlay onto the WIZ s pad you can also use the device as a menu selector Just place the cross hairs over your choice on the plastic overlay and click the button on the mouse to se lect The WIZ comes with Templates and 70 MODERN ELECTRONICS March 1990 WWW americanradiohistop esre _ Say You Saw It In Modern Electronics overlays for DOS and Windows By re turning the registration card you can get an additional template for free A num ber of templates and their correspond ing plastic overlays are available for many CAD word processing and other programs These additional templates cost 49 95 each Installing the WIZ gave me a little trouble The device is powered from the keyboard connector but must also be hooked up to a serial or mouse port There i
60. the unit on top of a 9V battery and you can hear every sound in an entire house up to 1 mile away Use with any FM radio Tunes to any frequency from 7O0mhz 130mhz Easy to assemble kit includes all parts and instructions Only 29 98 tax incl The WIRELESS TELEPHONE TRANSMITTER model WTT 20 is only about the size of a dime yet transmits both sides of a telephone conversation to any FM radio with crystal clarity Completely automatic Uses power from the telephone line itself never needs a battery Up to mile range Tunes from 70mhz 130mhz Easy to assemble kit includes all parts and instructions On ly 29 98 tax incl Cali or send MO VISA MC for immediate delivery Single kit orders Include 1 50 S amp H FREE SHIPPING on orders of 2 or more All orders shipped by U S Maii COD add 4 00 Personal checks allow 21 days DECO INDUSTRIES BOX 607 BEDFORD HILLS NY 10507 914 232 3878 CIRCLE NO 134 ON FREE INFORMATION CARD ELECTRON TUBES OVER 3000 TYPES IN STOCK Also capacitors transformers and parts for tube type equipment Send 2 00 for 26 page catalog ANTIQUE ELECTRONIC SUPPLY 46 688 W FIRST ST TEMPE AZ 85281 PHONE 602 894 9503 FAX 602 894 0124 Cable Converters And Descramblers Why Pay a High Monthly Fee For FREE Catalog Call or Write CABLE CONNECTION 1304 E CHICAGO ST SUITE 301 ALGONQUIN IL 60102 708 658 2365 No lllinois Orders 6805 MICROCOMPUTER DEVELOPMENT SYSTEM No
61. the work horse of this project It performs nearly all the functions illustrated in Fig 1 To accomplish this the chip has on board number of circuits which are diagrammed in Fig 2 Referring to Fig 2 BCD data ex cept the decimal point is presented at inputs a b c and d of the Input Say You Saw It In Modern Electronics ELECTRONIC SWITCHING ZT E f E Vul Le BCD TO 7 SEGMENT DECODER DRIVER 22 4 LINE ous ELECTRONIC SWITCH ELECTRONIC SWITCH CONTROL amp SYSTEM CLOCK 4 LINE BuS BCD DATA SOURCE 4 LINE BUSES Fig 1 Block diagram of the subsections that make up the project Data Buffers This data is written in to internal registers M1 through M6 when WE write enable and CE chip enable are low When implemented in the project presented here CE is permanently wired low When WE goes from low to high the data written into the registers is latched Address information is fur nished the 74C917 from a 74L 8390 IC4 in Fig 3 complete schematic diagram of project dual decade rip ple counter internal oscillator running at about 350 Hz switches the BCD data from the internal registers to the 16 x 7 ROM where it is de coded to hexadecimal format When SOE goes low segment drive data is switched to the proper decade in the display and turns on that decade Referring now to Fig 3 the dis play system clock generator consists of two stages
62. to ease this task Not shown in the lead photo are and light emitting diodes LED3 These were added to the prototype after the photo was taken Also not shown in the lead photo are the 5V POWER switch LED POWER indicator and and 5 OUT PUT binding posts you might have incorporated into your Power Supply project If you included this optional supply label the panel accordingly When you are finished labeling the panel mask off the controls switch es binding posts and display window with masking tape Then spray two or more light coats of clear acrylic over the legends to protect them from abrasion while the Power Supply is in use Allow each coat to dry before spraying on the next Finally when the acrylic coating has completely dried remove the masking tape and return the knobs to the shafts of the controls Closing Comments You now have a Dual Polarity Pow er Supply that is tailor made for op erational amplifier and other linear circuit experiments If you built into the project the optional 5 volt dc supply you also have a power source that can be used with TTL digital cir cults as well as mixed analog digital circuits You will never again have to resort to an arrangement of battery cells or kludge up a power supply when you need it 53597 UM a Dawe SX Soto s 5 p CIRCLE NO 132 ON FREE INFORMATION CARD www americeanradieohistorv com Put Professional Know
63. users to interchange Adobe Type 1 fonts across output devices The resulting device independence permits the same outline fonts to be used acrossia broad range of printers that use PostScript and AMT drive The printer is compatible with all models of Macintosh computers equipped with 1 MB of RAM and Apple system software version 6 0 2 or later It prints on plain paper and uses a printhead with self contained disposable ink supply that is rated to deliver up to 500 pages of text Both portrait and landscape printing modes are possible Resolution is rated at 192 x 192 dpi in quality mode 96 x 96 dpi in draft mode Connection between computer and printer is via a serial interface oper ating at 9 600 baud Rated operating noise level is 45 dB Five C size rechargeable cells not included power the printer and can print more than 100 pages of text be fore the battery requires recharging either overnight or while the printer is being used The printer comes with a 117 volt ac wall mount transform er for use when such power is avail able When the printer is in use built in software senses when data is being received from the computer and temporarily interrupts charging charging is automatically resumed after about minutes of inactivity The printer measures 10 8 W 6 5 D x 1 97 H and weighs 3 1 lbs 3 75 lbs with battery 699 CIRCLE 63 ON FREE INFORMATION CARD 16 MODERN ELECTRONICS March 1990 WWW
64. with its many features and 19 200 bps performance is perhaps your best V 32 dollar value today ME CIRCLE NO 117 ON FREE INFORMATION CARD Glossary of Popular Modem Terms ASCII 7 bit code for text encoding AT mode Hayes command set Bell 103 300 bps full duplex Bell 208 4 800 bps half duplex Bell 212A 1 200 bps full duplex Bps bits per second CCITT Cooperative Committee for International Telephone and Telegraph CRC Cyclic Redundancy Check error correction method Full duplex two way communication Half duplex one way communication ISDN Integrated Services Digital Network MNP 4 Microcom Networking Protocol error correction method MNP 5 Microcom Networking Protocol data compression method PLL Phase Locked Loop PSK Phase Shifted Keyed modulation PSTN Public Switched Telephone Network V 21 300 bps full duplex V 22 1 200 bps full duplex V 22 2 400 bps full duplex V 27 4 800 bps half duplex V 29 9 600 bps half duplex for use with fax V 32 9 600 bps full duplex V 42 CCITT error correction method compliant with MNP 4 Say You Saw It In Modern Electronics WWW americanradiohistorv com 1 800 826 7623 MESSAGE STOPPER Automatically stops your answering machine when you pick up any phone 515 95 ALL IN ONE REMOTE Tired of having 3 or 4 different remotes on the coffee table Then this remote is for you you
65. with the DIP switch turn on pow er and press and release the START switch to start the project counting down Bear in mind that it is possible to have more than one switch in the DIP switch assembly set to at any given time If more than one switch is set to on the snooze in terval will be shorter than if a single switch is closed because two timing resistors will be connected in parallel with each other So always make sure that only one DIP switch is closed for any desired countdown period A Rs ADVERTISERS INDEX page 132 Sales os ee 425 77 124 eee E 64 120 All TEIECIFOBICS 322022222222 81 Antique Electronic Supply 78 Antique Radio Classified 80 125 BAB Ine 20222222 22 59 80 140 CES Sales sena E 17 Cable 78 Cable Mate 80 Cleveland Institute of Elec 3 Command Productions 67 128 Consolidated Electronics 82 127 Cook s 58 CrutchDield 15 Damark International 53 71 134 Deco 78 8 Digi Key 79 Electronics Book Club Cov III 130 Fordham Radio Supply Cov IV 131 Franklin Belle Publishers 76 136 Global Cable Network
66. you properly wired the project For this you will need a dc voltmeter or a multimeter set to the dc volts function Clip the meter s common lead to the negative lug of 781 and leave it there until voltage measurements are complete Plug the project s line cord into an ac outlet and set the POWER switch to the 120 VAC ON posi tion Touch the meter s hot probe to pin 16 of the C2 and pin 14 of the and C4 sockets The readings obtained should all be approximately 12 volts If they are not im mediately power down the project and unplug it from the ac line Recti fy the problem before proceeding Once you are certain that the proj ect has been properly wired power it down and allow the charges to bleed off the electrolytic capacitors Then plug the ICs into the various sockets on the circuit board assembly Make sure the correct ICs go into the sock ets and that no pins overhang the sockets or fold under between ICs and sockets Handle these ICs with the same care as you would use in handling any other MOS type device Power up the project and calibrate it as follows The easiest way to ac curately calibrate the drive circuit to a particular frequency is with a fre quency counter that has adequate resolution Another method is to use the beat frequency LED to indicate the difference between the oscillator frequency and the 60 Hz of the ac line A third method isto use trial and error over a long
67. 000 WATT BLASTER DEFENSE WAND 89 50 ASSEMBLED EASY ORDERING PROCEDURE TOLL FREE 1 800 221 1705 or 24 HRS ON 1 603 673 4730 FAX IT TO 1 603 672 5406 VISA MC CHECK MO IN US FUNDS INCLUDE 10 SHIPPING ORDERS 100 00 amp UP ONLY ADD 10 00 CATALOG 1 00 OR FREE WITH ORDER INFORMATION UNLIMITED P D Bax 716 DEPT MEO AMHERST NH 03031 CIRCLE NO 126 ON FREE INFORMATION CARD EARN YOUR THROUGH HOME STUDY Our New and Highly Effective Advanced Place ment Program for expenenced Electronic Tech nicians grants credit for previous Schooling and Professional Experience and can greatly re duce the time required to complete Program and reach graduation No residence schooling re quired for qualified Electronic Technicians Through this Special Program you can pull ail of the loose ends of your electronics background together and earn your B S E E Degree Up grade your status and pay to the Engineering Level Advance HRapidly Many finish in 12 months or less Students and graduates in all 50 States and throughout the World Established Over 40 Years Write for free Descriptive Lit erature COOK S INSTITUTE OF ELECTRONICS ENGINEERING 4251 CYPRESS DRIVE z E JACKSON MISSISSIPPI 39212 CIRCLE NO 127 ON FREE INFORMATION CARD AMAZING PRODUCT EVALUATION Waveform of phase shift keyed PSK modulation and supported by virtually all popular communications programs like Cross Talk and
68. 022 Catalog amp Info 203 975 7543 CABLE TV BOXES Descramblers Converters FREE CATALOG TRANS WORLD CABLE CO 12062 Southwest 117th Ct Suite 126 Miami Florida 33186 800 442 9333 _ CABLE TV DESCRAMBLERS a BARGAIN HEADQUARTERS Complete w mini transmitter and 5 vdc RF receiver Fully assembled including plans to build your own auto alarm Write for more information Quantity discounts available b Check Visa or M C ONLY 24 95 30 days refund Add 3 shipping E ala VISITECT INC Dept M 415 872 0128 Oak M35B ONLY 60 PO BOX 5442 SO SAN FRAN CA 94080 6 month warranty We ship C O D T A Lowest retail wholesale prices FREE CATALOG Global Cable Network 1032 Irving St Suite 109 a ie H iin a n Artwork Made Easy S F CA 94122 PCBoards Layout Software takes the Hassle out of Creating P C B Artwork ORDER TODAY 800 327 8544 Advanced Features Menu Driven CIRCLE NO 136 ON FREE INFORMATION CARD Auto Router amp Schematic Program Available Requirements IBM PC or compatible 364K RAM DOS 3 0 or later PCBoards 99 00 Demo 10 00 AL 35205 205 933 1122 CABLE RENTERS STOP If your currently renting your cable equipm ent i s time to look into owning your own You can save upto 100 plus every year Satisfaction Guaranteed We carry all the major brands of Converters Remote co
69. 06 75 5523 RS150 Setot5 each of the 73 standard 5 9 90 P2022 2 1 28 10 35 74181AN 63 74H 240N 7 LM331N 5 25 AN7807 75 INS803 1N 6 3 50 1 2 watt carbon film resistors in the P2023 31 15 35 74153N 63 245163 238 75 tMi 1 65 AN7808 75 INSSO33N 11 3 38 senes 10 12 15 18 22 etc P2024 34 2 2 35 158 7481744 83 78 3352 2 10 AN7809 75 5803 6 275 through 10 megohms 365 tota P2025 22 3 3 35 74158 60 A 253 78 0 338225 120 75 INSO30N 11 563 E es 1 326250 1 20 AN7812 pcos M TAIHA 80 MOASIEN 75 NSBIERN 1750 MM ms2so of 5 each of the 72 standard 5 9 90 35 6800 P6370 72 10 35 AE rele 5 DE aaah jp 1851948 143 2 Bv 95 AN7820 75 m senes 11 13 16 2 0 2 4 etc 118 047 35 58 7441022 50 22 P6261 dM E 74S185N 143 eee LM338K 10 20 AN7BL04 43 MN 28 through 910 kilohm 1360 total pieces 50 33 P6371 2 P5262 i 2 35 63 SN 25 heen 4a 925 5 WIREWOUND REC RESISTORS 947 26 6263 a oa 3 35 FABON gp 738243N 350 90 MOORE 12 210 43 es 50 22 26374 35 6265 7452448 1 63 LM2340KC 15 210 lue 50 33 P6375 41 P6266 2 X 741814 250 105 12202993 135 Bh wsaots 87 43 amp DIA S AA
70. 1 inch length of small diameter heat shrinkable tubing over one primary lead of the power transformer Crimp the other line cord conductor to this lead and solder the connec tion Slide the tubing over the con nection to completely insulate it and shrink the tubing into place Then crimp and solder the other trans former primary lead to the other POWER switch lug on the same side of the switch Crimp but do not solder the center tap secondary lead of 77 to onelug of the fuse holder Then use a suitable length hookup wire to bridge be tween the same fuse holder lug and the negative lug of the screw type terminal strip on the rear panel of the enclosure Now wire the other half of S as shown in Fig 2 If the solder lug ter March 1990 MODERN ELECTRONICS 35 WWWw americanradiohlistorv com minal strip in the power supply is suf ficiently close to 781 simply bridge from the switch lug to the terminal strip lug to which the cathodes of all three diodes in the powering section connect If not lengthen the anode lead of D6 with hookup wire use heat shrinkable or other tubing to in sulate the connection Make certain D 15 properly polarized and that you wire the anode lead to S so that when the ac powering option is off the circuit from 751 is closed to D6 Now wire LEDI JI and J2 to the circuit board assembly using the wires you previously installed on the board Use small diameter heat shrinkab
71. 124 M 1276s X622 HC 18 173 1440 74151510 Si 74C374N 223 401BBCN 65 254234 2 10 2N2218 26 5161 36 M RS1X 5eachot values 100 to 97 62 29 95 B No tpfi 1V 10 41 59 15000 50 1 35 Ct 3 579545 X005 HC 33 234 1950 74LS159N 57 7409018 55 4047BCN 78 M 2N2235 2 30 2N27 194 zo PN2222A 23 480 total pieces PAO00 10 500 71 P4160 22000 50 195 45 HC 18 162 1350 7411548 1 34 7409078 55 40188CN 35 24238 230 202210 25 RS2X 5 cach of values 1009 to 9762 528 95 M P4002 15 500 64 P4100 100 500 68 346 X071 HC 1B 162 1350 7451858 60 74C903N 55 4049CN 33g 2 237 230 2022 80 982263 2 1480 total pieces P4003 18 500 64 P4102 1507500 68 M 3700 X012 HC G U 260 2290 40506 33 l 292232 230 282222 60 PN2484 2 4 P4004 22 50 64 4103 180 500 68 74151668 57 74C904N 5 RS3X 5 each of values 1 00 9 to 9 76KO 529 95 gt 1 000 X006 HC 18 162 13 50 74151578 54 74C905N 9 25 4051808 55 M 24239 2 30 2N2222A 60 PN2907 23 P4005 27 500 64 P4104 220 500 68 3 0320 X072 HC 18 162 1350 7ALSI58N 54 17409066 55 aD52BEN 56 284400 23 282363 60 PN2907A 23 480 total preces P4006 33 500 64 4105 270 500 B8 3134304 HC 18 162 1350 7405161 63 749076 56 40538C 55 M 204401 23 2 2369 60 3251 39 RS4X Seach of values 10 0KO to 97 6KQ 29 95 M 24007 39 500 64 P4106 330 500 68 1 13 50 TACSIBIN r MEIN 133 4060BCN 5B 284402 23 282405 1 at PN3565 28 480 total p
72. 1270 3 741500 TTL 74CD0 M 2p dile 73 DACYOZ2lEN 5 75 68 W ras 0018 50 122 P4715 0015 100 1 8 2 2 P6399 x T P it 181 Price CMOS 7AHCAD60N 1 10 Mi 200 497910 75 MMES6SARN 163 2 0 4577 0022 80 136 4716 0018 10 181 2 2 74 75 MMS38SEST 1 63 P4518 0027 50 138 7 0022 1000 1 7115004 32 74HC4075N 28 7912 5 21 32 Price 30 row 100 290 7 15 75 Available in 182 Watt ee ERE es 21 i Pasis 0033 50 1 47 718 0027 100 189 30 M 22 7 44 4719 0 033 1 1 93 74LS03N 32 prre i 7 306 164 M393N 51 AN7818 Interface How To Order Take any standard resistor value i 1000122 P6403 26 P6290 23 A cn a7 P4720 0 038 ioe 198 3T 28 150 LM395P 2 20 AN 920 151 1 SK and adda W1 for wau W2 Tor ME 100 33 P6404 23 d rue 26 P4522 0056 50 154 721 0 047 000 203 741505 32 74 08 45 74HC4538N 105 55 300 7324 75 Price M watt i e 1 5KW1 for 1 5KQ 7 wart this is the Dio 100 47 P6405 34 P6292 26 M 54523 068 50 163 P4722 0 056 100 2 10 741508 32 45 74HC4543N 1 37 1M3U5K 10 50 7904 43 0524888 88 Key part number 100 10 P6406 A2 P6293 3 4 A 173 P4723 0068 100 223 3 4000 26 21 00 Anglos 05 69 120
73. 12K displays to 1024 x 768 resolution One Centronics parallel port i Two RS 232C serial ports 80387 math coprocessor socket Includes software MS DOS 3 3 amp GW BASIC Zero wait state Mfg Sugg Retail Supports all VGA EGA CGA MDA 3 295 00 Hercules amp modes Dim 15 5 x 15 9 x6 1 qmm VGA Color Monitor DANMARK PRICE 14 high resolution tilt swivel monitor compatible 31 mm dot pitch Analog input signal Resolution 640 x 480 Full 20 Month Factory Warranty Factory New Factory Perfect 1999 Item No B 1842 133967 Insured dpt 39 00 I ET HAND HELD IMAGE SCANNER w Software Scanning maximum width up to 4 wide 100 200 dpi resolution Scans at approximately 1 per second Quickly reads signatures logos photos newspaper columns amp clip art Display bar charts 2 D or 3 D Scanner controller amp IMS Graphic Presentation software dithering patterns for grey scale effects Scanned images look as sharp and clear as the originals Works with major graphic amp desktop Mig Sugg Retail publishing software IBM compatible 00 Uses red LED amp CCD light sensors 13 different graph types w unlimited combinations Requires IBM or 10096 compatible 50 Q computer amp a hard drive Dim 5 75 Wx 1 5 H x 3 3 D Item No B 1842 134270 Insured Ship Hand 5 00 FOR FASTEST
74. 21 9 00 each STANDARD SIZE COOLING FAN Features die cast metal housing for strength and durability IMPEDANCE PROTECTED 4 11 16 square X 11 27 deep Factory new 120 Vac fans CF1 N 9 50 each TIL 99 PHOTO TRANSISTOR SWITCHES ITT PUSH BUTTON 1 25 volts 500 mAh CAT TMC 30 3 00 each e ons S seres SM X ge NCB AA 64 LED 4 10 for 9 50 WILL BUY 1 27 grey rectangular Mey se ied PHOTO FLASH CAPACITOR OC merci k SP ST NO fem Pu clans RATE DOA SEDE BI POLAR LED 1 4 WATT RESISTORS dm 0 25 amp carry current P C mount EE AM 200 mfd 330 volts RS Lights RED one direction Bent leads carbon comp and carbon film CAT4 PB 8 654 each 10 lor 6 00 Min 0 79 diameter X 1 11 high vj GRES 1 00 per assortment 100 for 50 00 SPDT PUSHBUTTON Marquardtit 1843 Rated 6 amps 125 250 Vac Black plastic pushbutton Switch body 927 X 94 X 657 CAT PB 18 1 65 10 for 1 50 each PUSHBUTTON SWITCH GC Thornsen 35 420 S P S T normally open momentary pushbutton switch Red plastic actuator 0 57 diameter Chrome r bezel 0 68 diameter Threaded bushing mounts in 50 diameter hole Rated 3 amp 250Vac Solder loop terminals PB 20 1 00 each 5 6 SIP IREED RELAY Electrol MIN
75. 4 7 1 4530 32 T4C85N 160 40 1BCN 2 LM741CN 51 9124 434 LOS 1 Watt Metal Resistor Assortments 74LS32N 32 8 a012BCN 2B x PANASONIC B SERIES 7415274 33 s ah EN 30 85101 5each of values 0 472 to 569 25 95 NA 7415388 33 74C90N 123 4014BCN 0 Digi K Pat a 222222 1255 total pieces yestar pac JaS42N 50 74693 123 30158CN 55 Puce 28542 23 f 85201 5 each ot values 629 107 ee Cap Volt Price MUSS 45174064 150 4018N 37 295550 30 wesi6384 23 B 1255 total pieces No VAC 10 7415558 38 4 107N 65 ROLE 1 147 25579 255 453641 30 RS301 5 each of values 8 2KQ to 1 OM 526 95 P455 51 50 105 TOSIA 42 74C150N 3 98 201680 M E 5 2956800 250 AP 2 255 total pieces P4552 0012 50 1 05 4 2N3438 175 APS3646 52 255 1491 299691 2 80 2 2 Wart Realstor Assortments P4553 0015 50 105 5 401548 3 88 3020 60 M 5 3706 v 00 2N5682 28D 5172 22 29 95 P4554 0018 50 1 05 85 221800 260 LDB 29769 32 weisst 258 total pieces S cds N i 2N5771 125 55514 24 noces 74LS85N 66 740161N 83 4023BCN 28 283803 23 2N5772 3 MPS8515 28 RS202 5 each of values 620 to 7 5KQ 29 95 QUARTZ CRYSTALS 283904 23 7415868 39 74C162N B3 40248 5 ELETT 141 285830 65 MPS6520 4 1255 tota pieces 250 22 1415904 51 74C163N 83 4D258CN 28 353905 73 2N5831 70
76. 5 811597AN 148 39 347 070 60 240 1 4007 1000 PIV 00 41 1 08 860 75 25 4164 10000050 P4431 1000 50 86 Busse Haa 52 205800 240 DH682 680050 90 P4432 1500 50 86 7417 AHC F352N 05 7 2200 33 pao oe 05 imzadan 52 7402008 E 5 CARBON FILM RESISTORS 200 1000 100 98 pagos 2200 50 B 7426N 35 J4HC32N 28 LESSEN 120 1 290550 390 170 Available in 1 8 1 4 amp 1 2 Watt P4203 2200 100 79 P4A35 2700 50 86 7427N 43 Part Pile 72 l 3578 1 50 quendi Les 48189N 210 8 How To Order Take any standard resistor value P4205 3300 100 79 P4436 6800 50 94 7430N 30 ay 23 74HC73N 39 LF398N 336 225 74828074 200032 and add an for 1 8 watt or a Q for 1 4 watt P4206 4700 100 109 P4437 10000 50 101 7432N 35 745038 35 JAHC74AN 36 1 105 M2917N B 225 7452888 17026 oran H for 1 2 wart 3 20 for 3 29 1 4 watt P4209 6800 100 1 P4438 15000 50 1 01 7437N 40 74HC75N 39 1 74 1 7452898 210 this is the Dig Key part number P4300 0144 25 56 4439 2200050 1098 733 N ag 74SO4N 38 LFA41CN 90 M2924N 26 g y part P4303 022 425 64 P 33000 50 173 UN 1 35 74HC76N 50 M LFasicNn TTE 748387N 195 prici 5 200 100 ub 4440 7440N 48 185058 35 JAHCB5N 85 Mm irasacn 180 12931250 66 345372AN 480 ricing 2 d P4305 0331 25 64 P444 47000 50 173 7442N 55 71S08N 35 pancagn 45 78 192
77. 5 00 200 ASSORTED 7 1 2 WATT RESISTORS AO Bent leads carbon comp and film GRABRE 1 00 per assortment 50 ASSORTED DISC CAPACITORS t I Most are cut p c leads Some to 500 volts CAT GRABDC 1 00 per assortment ELECTROL 2178 CONTROL Rated 5 510 10 y will operate on 3 32 Vdc LOAD 10 240 Vac 2 1 4 X 1 47 X 7 8 CAT SSALY 10B 9 50 QUANTITY DISCOUNT 10 for 85 00 25 for 175 00 50 for 300 00 100 for 500 00 15 VALUES OF ELECTROLYTICS Contains both axlai and radial styles from 1 mtd GRABCP 1 00 per assortment LOOK WHAT 2 00 WILL BUY 15 AMP SNAP ACTION SWITCH 5 pieces of a 15 OPTO SENSOR U shaped package with mounting ears 1 87 opening 3 4 mounting ears 125 250 Vac normally K5 a The inner workings of an electronic Scrabble game Op eds E ore yen open switch Body al T P erates on 6 Vdc B digit alpha numeric readout 45 but 1 34 X 5 8 X 58 ton keypad 14 transistors 2 1 piezo element and other goodies Top and bottom row of keypad buttons are function keys middie 3 rows are alphabetic No in structions available 6 X 4 45 5 4 1 75 each 10 for 15 00 TELEPHONE COUPLING TRANSFORMER Mull Products interna
78. 5 ME RE you explode mental blocks that hold you back DONDO BEACH 90278 Based on 40 years of research the CW Mental KINETIKITS from KINETICO electronic Block Buster uses guided meditation dynamic kits outputting light or sound Free catalog visualizations and powerful affirmations to KINETICO P O Box 1634 NY NY blast through mental blocks You can do 10114 0508 code That means new bands more contacts more fun This is not a CW practice tape EXTENDED PLAY CASSETTE RECORD The CW Mental Block Buster audio cassette ERS 12 hours per standard cassette VOICE and practice booklet are only 24 95 ppd in ACTIVATED Also brief case recorders the US NY residents add 1 87 sales tax phone recording adaptors Free brochure Quantity discounts available for classes Productive Products Box 930024 Norcross PASS Publishing Box 570 Stony Georgia 30093 Brook NY 11780 ee C 78 MODERN ELECTRONICS March 1990 Say You Saw It In Modern Electronics WWW americanradiohistorv com llig KBy 1 800 344 4539 CORPORATION AK Puerto Rico 218 681 6674 FAX 218 681 3380 TWX 9103508982 DIGI KEY CORP INTEGRATED CIRCUITS INTEGRATED CIRCUITS SILICON TRANSISTORS PANASONIC SU SERIES __ DISC CAPACITORS
79. 52 RESEDA BLVD DEPT ME RESEDA CA 91335 No Collect Callis 818 716 5140 IMPORTANT WHEN CALLING FOR INFORMATION Wwww samericanradiohistorv com Please have the make and model of the equipment used in your area Thank You March 1990 MODERN ELECTRONICS Copyright 1 987 PACIFIC CABLE CO INC 5 TALK IS CHEAP Have you heard For less than 90 your AT or XT compatible com puter can talk All it needs is the HV 2000 Computer Voice Kit from Heathkit Reading letters transcriptions and computerized instruction can be easier and quicker than you ever thought possible Computer games gain a new dimension Your com puter can even entertain children with stories 4 and songs CT a you have modem the HV 2000 Computer Voice will allow your computer to recite reference and research information from time sharing services Or speak radio transmitted ASCII information The HV 2000 Computer Voice Card containing speech synthesizer and audio amplifier plugs into any AT or XT compatible computer s expansion slot An external speaker is also included Versatile Heath developed software gives you a wide variety of voices and easy in terface to high and low level languages The HV 2000 Computer Voice At less than 90 talk IS cheap To order call toll free 1 800 253 0570 Use your Visa MasterCard Amen can Express or Heath Revolving Charge card Use order code
80. 55560 41 85302 5 each of values 8 2KQ to 1 0M 329 95 250 33 adn 4 28 Freg Digi Key Pricing 2415934 y 146163 123 RU 25 73962 118 295833 56561 45 1255 tota pieces 9 47 512 21 MHz Par No Case 1 10 741510 240156 12 N5961 1 MPSot 4 250 100 19 74L8108AN 45 7401738 ai A0288CN 75 284020 it hee 35 ed dH p 1 METAL OXIDE FILM RESISTORS 450 1 0 P6193 47 1 000 X045 HC 33 1008 8400 36GUAN 45 1 _ 55 403008 30 ns 7125 286125 49 MPSAI2 52 Available in 1 4 Watt 250722 1 000 5 125 213 0 113 24058 150 130 55 How To Order Take any standard resistor value ie 15047 188200 0679 342 7850 2415125 48 740193N 110 40358CN 75 2841223 23 2N7184 15 MPSA42 45 1 69K and add an X ie 1 69KX this os the Digi 450 10 20000 X068 HC 18 3 24 21 00 741512644 BO 740195 78 30408 60 M 2x312 23 2N1132A 204 MPSA43 45 part number Au 1 2 4576 X047 HC 33 378 3150 74151329 63 7462210 1 50 1404108 63 2N4125 23 N1613 92 5 92 45 Pricing 5 200 1 00 E 2 4576 X069 HC 18 3 06 25 50 74151484 54 74C240N 198 40428CN 63 BM 2 126 _23 2N1893 14 MPSASI 45 M sa wat 50 780 30 00 2 5000 X070 HC18 30 2850 74 51384 54 74C244N 1 98 4043BCN 63 M 2u4208 1 26 2N2218 95 MPSLD 36 048 ro 378 3150 1451399 601 746373N 2 23 4044808 63 4205 210 QN 218A 95 PN2222 24 y 1 4 Watt Metal Film Resistor Assortments Part Cap Volt Price pi 58 10000 50
81. 620 001 For your FREE Heathkit Catalog call 1 800 44 HEATH Heath Company A subsidiary td Zenith Electronics Corporation Prices product availability and specifications are subject to change without notice CIRCLE NO 141 ON FREE INFORMATION CARD WI EDITORIAL IER Trying It Out There s nothing like actually using a new product type to get a true feel for its utili ty All the news press releases in the world won t prepare one for the experi ence During the past year I tried out a bevy of new product types that under scored this fact of life Most recently I got my hands on Seiko Instruments newly introduced Contractor product It s a handheld de vice that simplifies taking room measure ments and calculating the amount of ma terial needed for construction or decorat ing purposes If you ve ever measured a room s dimensions with a tape measure in order to figure out how much paint wall panels floor tiles ceiling tiles wall paper or carpeting would be needed you ll certainly appreciate what this bat tery powered tool can do for you Just point and shoot and the measure ment automatically appears in a liquid crystal display Although I couldn t get technical de tails I believe that the instrument uses Polaroid s ultrasonic measuring system In use you hold the unit steady general ly by placing its back on a wall and press a button that s located on both sides
82. 74152938 40 82 4527BCN BB IiMIBDON 195 AN79M09 63 ML 4817 P4133 2700 1K 2 93 P4420 2200 25 75 74028 35 74153524 147 14 00 48288CN 83 LM180 N 135 AN79M 63 3301k 281 300008 F 7403N 35 745265 54 cmos 4529BCN 83 1 180229 12 30 79 12 63 P4135 3900 1 4 46 P4422 4700 25 75 7404N 35 7415266 54 64 Price 531 7B LM1830N 2 55 AN79M15 63 Par P4136 4700 1K 5 36 P4123 6800 25 83 74058 43 7453674 54 j4urgow 3 54 30 1M1870N 300 AN7SM 8 83 M No Description Pkg 1 10 1000 1 000 P4137 S600 1K 5 36 P4424 10000 25 83 740BN 48 73153688 60 74HCOZN 28 B 27238CN 95 1M1871N 240 AN79M20 3 4001 50 PIV DO 41 20 5 60 49 00 P4138 6800 1 8 24 P4425 15000 25 90 74 18 74152738 65 24BC 3 1M1872N 255 ANJSM24 83 75 600 52 50 P4139 8200 IK 814 P4426 2200025 94 O7N 74HCO4N 28 4724BCN B 1N4002 100 PIV DO 41 P4140 10000 1K 8 44 gt 125 84 7408N 43 74 8374N 65 74HCOBN 28 LMT875T 525 Memory 1 4003 200 00 41 80 640 56 00 P4161 10000 50 86 47000 25 55 74094 43 74156704 143 T4RCi N 28 Linear 1M1889N 216 1NA004 400 PIV 00 41 85 680 59 50 AE 10000 a0 amp 78100 43 811595 191 Prica LM230ON 150 Part Price 1 4005 600 41 88 7 00 61 25 69000 7414N 50 ansggan 148 28M 720 iM2901N 60 MMZ147N 1750 1N4006 800 PIV DO 4 58 780 6825 4163 47000190 101 P4430 100000 25 19 7416N 3
83. 837150 95 7asa73an M 1 8 Wate 5 640 2500 7445N 98 745098 38 7ancio7N 53 270 23310 9 345478 480 1 4 Watt 5 340 1300 131 un aie a 4HC112N 53 LMT ICIN dH pite 38 745475 480 1 2 Watt 25 350 1600 113 si pisc 248500 1 Watt Redistor Assarments 1 28 7451N ag 74820N 38 74HC 25N 48 LM301AN 57 1 3089 2 5 745572N 4 50 RS112 Set of 5 each of the 73 standard 5 9 90 1 91 74538 34 145228 53 j4uC128N 53 B LM307N 75 1 3301 99 34557144 459 1 8 watt carbon film resistors in the 1 91 7459N 3p 745308 481 28 LM 308A 30 LM3302N 99 senes 1 0 12 1 5 18 22 etc 221 7460N 34 ei 74HC 14RN 45 LM311N 54 LM3401N 1 0 Mi 1 0 megonm 1365 total 27 7473N 4p 7 Jaut 138 45 495 LM3524N 373 10 3 7474N 48 73951N 45 CIT E M31 712 92 us Pan Price B 85212 Set of Seach of the 72 standard 5 9 90 2 9 7475N 50 74SB4N 45 74HC151N 55 LM317MP BE LM3 05 E0P402N 135 1 8 watt carbon lilm resistors the 7426N TA EEREN 23 74HC153N 55 99 LM3809N 150 0 112 series 1 1 1 3 1 6 2 0 2 4 etc 7 465M 70 1 E P498N 5 38 through 910 kilohm 360 total pecas 745869 i JAHC154N 1 13 i Les pe 21 0 49 j Cap Volt Price 233125 34 A en yap 60 53 S9 LM3GI5N 285 COPA99 538 1 4 Watt Resistor Assortments No 1 33 25 32 7490N 55
84. Answering Machines Part What they are how they work and tips on buying the right model for your application By Stephen J Bigelow ccording to a recent report sales of telephone answer ing machines rose from 3 million to nearly 8 million units in just five years with purchases for home office use accounting for al most 2 5 million units alone Sales are still going strong making tele phone answering machines among the hottest personal convenience communications devices in the marketplace Modern answering machines make widespread use of VLSI very large scale integration and custom inte grated circuits that have been one of the primary reasons for shrinking of both sizes and prices These IC de signs have also contributed to pro viding sophisticated capabilities that were not available in the most expen sive of machines only a decade ago As a result these machines are com monplace in homes for personal use and in business for professional use In this installment we will cover the basic operating principles of tele phone answering machines and de scribe the various features and func tions you can expect to find in con ventional models Next month in the Conclusion we will detail important machine installation and mainten ance procedures Record Call s Model 2140 answering machine with digital numeric message counter and built in telephone instrument The Components In spit
85. DC 0834 and ADC0838 All converters in the ADC08031 series ADC08031 series features easy interfac ing with a wide variety of microproces sors and microcontrollers and supports National s MICROWIRE interface The new converters use a successive approximation conversion technique Track and hold permits signal sampling at rates up to 100 kilosamples per second on the ADC08031 and 80 kilosamples per second on the ADC08038 Input voltage range for all devices is from 0 to 5 V us inga 5 V reference and operating on a 5 V supply Digital I O lines are TTL and CMOS compatible ADC08031 and ADCO08032 are available in a choice of eight pin plastic DIP and CERDIP packages The ADC 08034 and ADC08038 are available in 14 pin and 20 pin wide body SO packages respectively in addition to plastic DIP and CERDIP packages devices in the ADCO8031 series are available in extend ed industrial 40 to 85 C and mili tary temperature range 55 to 125 C and in two electrical grades providing VLSBor 1 LSB maximum total un adjusted error ME Be anFCC 580 DUCI FERIIS TECHNICIAN ean 188 ER Earn up to 30 an hour and more Learn at home in spare time No previous experience needed No costly E Eoo No commuting to class The Original Home Study course pre pares you for the FCC Commercial Radio telephone License This valuable license is your ticket to t
86. E also has several other ways to prolong battery life such as a standby mode that shuts down the system after 10 minutes of non use There is also a stand by pushbutton that when pressed also puts the LTE into this mode To bring the system back to life just press the standby button again The battery pack inciden tally is replaceable and the 286 LTE has non volatile RAM This means that when the battery runs out in the middle of a task you can pop in another fully charged pack if you buy a second battery and keep it charged without losing any data The battery takes about eight hours to fully recharge and the system can be used on ac power with the ac adapter while this is taking place Compag also offers an optional exter nal Fast Charger that can recharge the battery in just an hour and a half This optional Fast Charger also features a deep cycle charge that minimizes the memory effect that plagues Ni Cd bat teries In addition the LTE and 286 LTE use the low power CMOS version of the 8086 and 80286 80C86 and 80C286 CPUs to make best use of available bat tery power Even though it s small and light weight the LTE and 286 L TE offer the same connectability that you d expect from a larger system There is a fold down panel in the back of the PC that covers the serial and parallel ports Also located on this back panel are a connec tor for attaching an external CGA moni tor external keypad connector for th
87. ELECTRONICS March 1990 WWW americanracdiohistaru eaena Say You Saw It In Modern Electronics JH LEARN VCR CLEANING MAINTENANCE REPAIR EARN UP TO 1000 A WEEK WORKING movement keys and HOME PgUp PgDn INS DEL and END functions located on the embedded cursor pad These func tions as well as cursor movement are also available on a set of four arrow keys on the bottom right of the keyboard Again the locations of these keys takes getting used to Aside from having to get used to some of the key locations the 286 LTE is a very usable system Running at the same 12 MHz clock speed as the DeskPro I normally use at work I noticed no differ ence in speed in performing the same word processing spreadsheet or other applications usually run on the desktop system The two most noticeable differ ences are the screen which is an electro luminescent backlit supertwist LCD with CGA resolution rather than the color VGA on the desktop and the hard disk In an effort to conserve battery power the disk is turned on and off as needed When you perform a disk operation such as loading a file or saving the disk is turned on It takes several seconds to come up to speed and runs on for a while after the disk operation is performed If you are doing disk intensive tasks the drive will be on almost constantly other wise it will cycle on and off as needed prolonging the useful battery charge The LT
88. IATURE TOGGLE SWITCH S P D T ON ON Rated 5 amp 120 Vac Solder lug terminals Li CAT amp 5 4 1 35 each 10 for 12 50 100 for 110 00 tion 1 X 375 CAT RRLY SIPS 1 10 each Aromat RSL2D 5V MInlature SPDT dual coil latching relay 5 ALL PLUG DIRECTLY INTO 120 VAC OUTLET 12 500 125 4 50 6 200 DCTX 520 225 9 Vdc 1 CAT DCXT 051 55 0 24 Vac 625 ma CAT ACTX 2462 325 S P D T Omron G2E 184P 4 contacts 335 ohm coil Sugar cube size RLY 787 CALL OR WRITE FOR OUR FREE 60 PAGE CATALOG OUTSIDE THE U S A 4000 2 00 POSTAGE PARTS FOR A CATALOG NILS CORN 6 826 5432 por ds E MLL ELECTRO saris 1 80 Build this variable speed led chaser 10 leds flash seque tally at whatever speed you set them Easy to build kit includes pc board parts and instructions Ideal for special lighting effects costumes etc Operates on 3 to 9 volts PC board 15 5 X 2 25 A great hour project CAT AEC NICKEL CAD TO 18 case with window For wide angle viewing B ATT E R S STANDARD JUMBO Two LE D s flash In We applications Spectrally and mechanically compat ECHARGEABLE 5 DIFFUSED T 1 3 4 sze unison when 9 volt zf x ible with TIL 318 TIL 99 CE a avo
89. Kel vin It features a built in diffuser Say You Saw It In Modern Electronics VC 6025 20MS S 50MHz Bandwidth 2K Word Memory Capacity 2349 00 Advanced storage functions create new dimensions in scopes such as one shot observation flicker free display bnght display ior even high speed event trace observation for low speed event hard copy by plotter and data output to compute VC 6045 100MHz 40 5 5 4K word Memory cap call All Hitachi Scopes include probes schematics and Hitachi s f 3 year worldwide warranty on parts and labor Many acces sones available tor al scopes 375 0 1251 6 CRT Built in component tester 1 65MHz 1x 10x TV Sync e 94 AI 40MHz 40MHz 40MHz 60MHz 100MHz 100MHz QT T imV sens Delayed Sweep Cursor DVM Counter 150MHz FREE with purchase of ANY SCOPE SCOPE PROBES P 2 100MHz 1x that spreads the light out evenly and eliminates glare A lightweight Ni Cd battery pack which clips onto the light provides power for up to 20 minutes The battery pack can be recharged hundreds of times with the charger supplied with the light The Powerlight mounts onto the light shoe of virtually any cam corder 129 95 CIRCLE 61 ON FREE INFORMATION CARD 212 435 List 55 Save 160 DC to 20MHz Dua Channel ss v V 1060 List 1595 OU Channel Delayed Sweep CRT Readout Sweep
90. N A U Mh O 21 22 23 24 25 26 2 28 From Pin mt U O tA 9 10 11 12 13 14 5 16 74C917 Ground C4 pins 6 15 1C6 thru IC11 Pin 3 C6 thru IC11 Pin 4 C6 thru IC11 Pin 5 thru IC11 pin 6 No Connection Ground Q6 Base Q5 Base Q4 Base Q3 Base Q2 Base Q1 Base Ground IC4 Pin 7 R2 R3 5 Volts CZ R4 RS R6 R7 No Connection C4 Pins 12 13 ICS Pin 1 IC3 Pin 9 IC4 Pin 11 ICS Pin 2 IC3 Pin 10 IC4 Pin 10 ICS Pin 3 IC2 CD4049 To 5 Volts Cl Pin 1 IC2 Pin 4 R9 R8 No Connection No Connection Ground No Connection No Connection No Connection No Connection No Connection No Connection No Connection No Connection From Pin 2 3 4 5 6 8 1 4 1 1 1 2 QN ND ON IC3 74LS00 To No Connection No Connection No Connection No Connection No Connection No Connection Ground IC3 Pins 12 13 C4 Pin 14 5 Volts 4 741 5390 IC2 Pin 2 Ground IC4 Pin 8 C4 Pin4 IC6 thru IC11 Pins 7 C6 thru IC11 Pin 10 IC4 Pin 6 ICI Pin 16 No Connection 5 Volts IC5 74LS138 From Pin To Ground Ground 4 5 Volts No Connection Ground No Connection IC11 Pin 1 IC10 Pin 1 IC9 Pin 1 IC8 Pin 1 IC7 Pin 1 IC6 Pi
91. NG because Call Waiting often uses short pulses for other functions which can easily confuse an answer ing machine and cut off a caller in mid sentence if the switch is set to the SHORT position If in the LONG mode the machine records a lot of unwanted sounds dial tone or a hang up alarm from the central office for example after the caller hangs up the machine is not interpreting the long CPC pulses The solution to this is to set the CPC switch to the SHORT position If the machine still does not disconnect promptly and continues to record un March 1990 MODERN ELECTRONICS 21 Say You Saw It In Modern Electronics Caller says Hi call me soon T Telephone AUDIO BUS Telephone network coupling and R Switching network VOX SENSE Message duration timer switch c 1 MIN Record ICM fiie Main Pand VOX uration gt timer START Head Speaker Hi call me soon Speaker i amplifier e Mee Voice signal ICM record amplifier Drive motor Motor driver Fig 4 Control Circuit switches in internal speaker to permit everything caller says to be reproduced through speaker wanted noises the central office in your area may not be equipped with CPC signals In this event set the CPC Switch to OFF Disconnection occurs automati cally when the preset recording time expires or the VOX sensor signals that the caller has stopped talking for more than a few seconds After t
92. Peg 14995 WWW americanracdiohistorv com em Pr e ww m Tm w oy mmn mee gt Scores a SCOPE Pocket Size Audio Signa Generator Sine square wave patterns 20Hz to 150 KHz Battery operated Frequency accuracy 3 or 1655 Output 12V rms max load Low battery indicator Test leads amp 9V battery included 0 Model RC 555 Reg 56995 99 0 9 ao M o ae o see N Service amp Shipping Charge Schedule Continental U S A FOR ORDERS 0 50
93. RD 4 MODERN ELECTRONICS March 1990 18 24 31 38 50 54 60 65 68 d OC 14 53 82 VOLUME 7 NUMBER 3 FEATURES Telephone Answering Machines Part I What they are how they work and tips on buying the right model for your application By Stephen J Bigelow Dual Polarity Power Supply Dc voltage source that is adjustable from 1 2to 37 volts and has built in digital numeric metering By Tim Swogger A Tide Clock Keeps track of the rise and fall of water affected by ocean tides By Joseph P O Connell BCD to Hex Converter Display Easily converts and displays binary coded decimal data in hexadecimal format By Lloyd W Redman Using an Oscilloscope in Electronics Troubleshooting Testing overshoot and ringing of square waves shock excitation of RLC circuitry and transient waveforms in pseudo inductive circuits By Robert G Middleton A Pocket Snooze Alarm Lets you catnap for selected periods of 5 10 15 or 30 minutes before being awakened by the battery powered alarm By Homer L Davidson PRODUCT EVALUATIONS The Racal Vadic V 32 Modem High Speed Data Communications on a Budget By TJ Byers COLUMNS Electronics Notebook Experimenting With an r f Spectrum Analyzer By Forrest M Mims III Solid State Devices Analog to Digital Converters By Joseph Desposito PC Capers The Winter 1989 COMDEX Report By Ted Needleman DEPARTMENTS Editorial By Art Salsberg
94. RN ELECTRONICS March 1990 Say You Saw It In Modern Electronics WWW americanradiohistorv com PARTS LIST Semiconductors D1 through D8 1N4004 or similar silicon rectifier diode or substitute 100 PIV 5 ampere bridge rectifier modules see text DISP1 DISP3 DISP3 Common anode 7 segment LED numeric dis play MAN72A or equivalent IC1 LM31I7T adjustable positive volt age regulator IC2 LM337T adjustable negative voltage regulator IC3 7805 fixed 5 volt regulator IC4 CA3161E BCD to 7 segment decoder driver IC5 CA31262E three digit dual slope A D converter LED1 LED2 LED3 Jumbo red light emitting diode Q1 Q2 Q3 2N3906 or similar general purpose npn silicon transistor Capacitors C1 0 33 pF 16 volt Mylar or other type C2 thru C6 0 1 pF 50 volt ceramic disc 7 10 35 volt electrolytic C8 thru C12 470 4F 50 volt elec trolytic Resistors 5 tolerance R1 R2 220 ohms R3 R4 R5 330 ohms R6 1 ohm 4 watt or greater R7 1 000 ohms R8 100 000 ohms R9 10 000 ohm pc mount trimmer potentiometer R10 50 000 ohm pc mount trim mer potentiometer R11 R12 5 000 ohm linear taper panel mount potentiometer Miscellaneous BP1 BP2 BP3 Five way binding post color coded for easy visual identification of polarity F1 0 5 ampere slow blow fuse 51 52 4 switch S3 Spst toggle or slide switch T1 40 to 70 volt rms center tapped power transform
95. RONICS THEORY 2926 25 95 a ae CIRCU iT BOARDS 1 With 17 Projects 3155 19 95 2898 23 95 E BEGINNER S GUE TO TV REPAIR wach eor Mins wales LASER PHASER IONS RAY GUN SPARE ROLY for only 5495 values to 130 70 and get a FREE Gift 1897P 14 95 1604 517 95 BUILD YOUR OW CUSIPATIBLR AND SAVE CIRCUITS 3195 28 95 ET 2831 us Counts as 2 15 95 1938P 29 95 Counts as 2 3156 23 95 Electronics projects ideas the latest technology all at up to 50 off publishers prices Membership Benefits Big Savings In addition to this introductory offer you keep saving substantially with members prices of up to 50 off the publishers prices Bonus Books Starting immediately you will be eligible for our Bonus Book Plan with savings of up to 80 off publishers prices Club News Bulletins 14 times per year you will receive the Book Club News describ ing all the current selections mains alternates extras plus bonus offers and special sales with scores of titles to choose from Automatic Order If you want the Main Selection do nothing and it will be sent to you automatically If you prefer another selection or no book at all simply indicate your choice on the reply form provided As a member you agree to purchase at l
96. S kz A Winning Project e My Talking Telephone Modern Electronics October 1989 has been se lected as one of the top nine circuits by the Design 89 International Design Awards committee Sponsored by the Electronic Component News and OrCAD the De sign 89 Awards is an annual event that gives top engineers in the country recog nition for their contributions to the ad vancement of the electronics industry for the previous year It was held in the Civic Auditorium Brooks Hall Moscone Convention Center in San Francisco November 14 through 16 1989 Steve Sokolowski Component Availability Readers who read my Stepping Mo tors article in the January 1990 issue of Modern Electronics may have difficulty in locating a source for the IC chips refer enced in the text Both theSMC20 an up LOOK NO FURTHER graded version of the referenced SMC10 programmable indexer and AA8416 driv er are available directly from Anaheim Automation 910 E Orangefair Lane Anaheim CA 92801 tel 714 992 6990 While on the subject of the Stepping Motor article there are two errors that should be corrected In Table 1 under the heading Phase 4 the entries should be off on off and off from Step 1 through Step 4 The other is in the seventh line in the center column of the main text on page 21 The figure 0 15 inch should be changed to 0 00015 inch This would make the final two figures in this para graph 5 00015 an
97. SL i 5 wo 56 1000 100 22 P6407 48 P6294 0 24524 0982 50 13 P4724 0082 100 2725 741810 32 74C20N 25 MS55CN 75 79106 43 051488 85 W x 100 33 P6408 54 P6295 46 P4526 0 12 50 1 88 725 0 17100 230 14511 32 74C30N 45 Pan Price 55 90 AN79107 13 7E450N dd My 2 1200 5600 10150 100 47 P6408 57 P6296 P452 015 50 195 4726 012 100 2 57 2415128 32 7AC32N 48 4Q01BEN 27 LM585CN 195 79108 431754510 70 gt 100 100 P6410 82 P6297 BI P4528 0 18 50 201 P4727 015 100 265 741514 48 74C42N 05 400288 10 5 156 AN7SLOS 43 754528 0 100 220 Pen 122 P6296 109 M Pas 022 50 210 728 018 100 2 75 741515 36 5 4 ADOBBCN 63 LMSB7CN 111 ANZSLIO 43 754538 70 11 0 1 0MQ _15__ 0 9 00 4000 7250 100 330 P6412 1 54 P6299 1 32 P4530 027 50 245 P4729 022 100 294 745208 32 729408 K 7 453N 70 100 470 P6413 202 P6300 1 22 74673 65 400728 28 M iw 09CN 15 AN SL12 4831 53 2 Watt Hu P453 0 33 50 2 79 P4730 027 100 334 74LS21N 32 63 00BCN 65 M w722CN 75 AN79115 43 7 ASIN 1 00 0 47 0 919 23 1 00 13 15 940 100 40 M 100 1 000 P641 94 PA532 039 50 310 P4733 033 100 381 7415258 32 740768 55 J009CN 35 M 25 270 AN7SI1B 13 7492 112 M 2 wat P4533 0 47 50 345 4732 039 100 422 74 527 32 746838 1 60 4010CN 3B M733 N 84 AN79120 43 d aces 1 0 1 0M9I 18 1050 4750 8750 4534 0 56 50 3 14 P4733 047 100
98. The pulsating dc emerging from the rectifier assembly is fed to filter capacitors C9 in the negative supply and 2 in the positive supply sec rm ud tions The reference point for the two supply sections is established by connecting the center tap of the transformer to circuit ground Once the pulsating voltages are fil tered to pure dc they are fed to ad justable voltage regulators JC in the positive supply and 2 in the nega tive supply From the outputs of both regulators the final voltages fed to and BP3 where they are made available for external use This makes up the basic Dual Polari ty Power Supply The remaining cir cuitry is for metering purposes Adjustment range for the positive and negative supplies 1s provided by POSITIVE and NEGATIVE adjust con trols R77 and R12 respectively Ca pacitors C77 and C10 provide post regulation filtering for and 1 2 Say You Saw It In Modern Electronics March 1990 MODERN ELECTRONICS 25 SUUM ammo a SANL COAN eh ee Er R6 01 04 IN IC1 OUT BP1 1N4004 LM317T R1 V x T1 n E 40 70Vac CT e C5 470uF 2 7 10 Cs 41 470 R2 eco BP3 D5 D8 1N4004 alind EN Tc internal circuitry o GND 117Vac B A T 44 520 S2C o S2A 13 e 51 N d IC5 164 4 162 CA3161E LED2 26 MODE
99. Time Autoranging Trigger Lock 1 359 2mV Sensitivity SAVE 1mV sens DC Offset Vert Mode Tngger Alt Mag 1mV sens Delayed Sweep DC Offset Alt Mag 1mV sens DC Offset CRT Readout Cursor Meas 2mV sens Delayed Sweep CRT Readout 2mvV sens Deiayed Sweep CRT Readout Cursor Meas 1mV sens Delayed Sweep CRT Readout DVM Counter 1 070 1 295 1 895 52 450 3 100 200 200 221 150 35MHz Dual Trace Oscilloscope DMM 495 M0 1252 1mV Sensitivity 19 95 10ns Rise Time 10x 23 95 Delayed Triggering High luminance 6 CRT 6KV Accalaratlon Voltage X Y Operation Z Axis Sweep Top quality scopes at a very reasonable price Contains all desired features Two 1x 10x probes diagrams and manual Two year guarantee PRICE BREAKTHRU on Auto Ranging DMMs EM 135 choose from 1180 24 95 05 DC Accuracy gt 1 Resistance BEC 2 2 88 Transistors and with Freq Counter True RMS 4 Diglt Multimeter M 7000 mm and deluxe case D MDM 1181 27 95 1182 29 95 3 1 2 LCD Display 27 Functions Auto Manual Ranges Audible Continuity Data Hold MDM 1182 1 Accuracy MDM 1181 f 1 M 3500 o accy 05 Soldering Station Temperature Controlled 5120 99 Digital display ot ange Grounded lip Overheat protect Finest in the industry 10 rock sleady patlerns Wide Band Signal Genera
100. a BCD format source This gem of a chip is just what you need to relieve you of the headache of having to la boriously make BCD to hex conver sions either mentally or with a spe cial type of calculator The BCD to Hex Converter Dis play project described here takes full advantage of the National chip It offers a full six digits of display that requires no interpreation Just feed in BCD data and numeric displays automatically show its hex equiva lent The project can be used to con vert and display up to 24 bits of BCD data from any source as long as the data is latched temporarily stopped to provide a stable display About the Circuit When designing a decoder display driver circuit several functions must be performed The sequence of events is illustrated by the block dia gram shown in Fig 1 To begin with the BCD data to be displayed must be latched tempo rarily stopped at the Data Source Next the latched data must be CORN gt jou J 2i 2 9 79 e DE P I LU PS 4 pe cm t Can A gt cer 1 LUT Ce 9 A 5 d roa Que p i r E ww ww www LE i 1 24 gt 24 I a ad 3 switched four bits at a time by the Electronic Switch to a BCD to 7 Segment Decoder Driver T
101. acle 501 Also drill a hole to provide entry for the ac line cord Machining details for this pan el are shown in Fig 6 After all machining is done deburr all holes and cutouts to remove sharp ED1 CATHODE Fig 4 Component placement guide for pc board Say You Saw It In Modern Electronics edges Then paint the front panel if desired When the paint has fully dried label the front panel with a dry transfer lettering kit Protect the lettering with two or more light coats of clear acrylic spray allowing each to dry before applying the next When the enclosure is ready mount the circuit board assembly in place with suitable length spacers and 4 40 machine hardware Mount the power transformer solder type terminal strip and fuse holder into place Then referring to Fig 2 care fully wire the power supply circuit Make certain that you do not mistake the primary leads of the transformer for the secondary leads and that the diodes are properly polarized Place a rubber grommet in the the ac line cord s entry hole in the rear panel Then feed the unprepared end of the line cord through the hole and tie a strain relieving knot in it about 8 inches from the free end inside the enclosure Tightly twist together the fine wires in each conductor and sparingly tin with solder Mount the various components on the front panel Then crimp and sol der one line cord conductor to one lug of the POWER switch Slip a
102. allow any popular pro grams to work inthe VGA mode that do not otherwise support this stan dard Special extended resolution drivers are also included for popular software This card supports in addition to VGA monochrome MDA color graphics CGA enhanced graphics EGA gray shades MCGA and Hercules graphics standards Switch ing among the various operating Portable Printer for Macintosh Computers Kodak s Diconix Model M150 plus battery powered ink jet printer for use with Apple Macintosh comput ers is an enhanced version of the Model 150 plus printer It was de signed to be a traveling companion for the new Macintosh portable and other totable Mac computers Its small footprint occupies minimal desktop space The printer comes with the new Adobe type manager software that builds type at any size from PostScript outline fonts All 13 PostScript outline fonts provided in the original Apple Laser Writer printer are included in the ATM package Also supplied is MacPrint a QuickDraw printer driver that in stalls in the Macintosh system folder and appears as a printer choice in the Chooser menu When printing text MacPrint driver and ATM automati cally generate printer font bit maps from font outlines optimized for the M150 plus printer s full 192 x 192 dpi resolution The bidirectional print er uses QuickDraw routines to image graphics This software combination allows
103. already pub lished Here we discuss overshoot and ringing in square wave tests shock excitation of RLC circuitry and transient waveforms in pseudo inductive circuits n previous issues of Modern Basic Ringing Shown in Fig 1 is a basic test setup for displaying a ringing waveform in an electronic circuit It uses a gim mick that consists of two or three turns of insulated wire wound around the lead to the inductor and capaci tor This provides a small amount of capacitive coupling from the square wave generator to the LC network and minimizes circuit loading Similarly a low capacitance probe 15 used with the oscilloscope to mini mize circuit loading The square wave generator must have a fast rise time to assure that sufficient har monic energy is applied to adequate ly shock excite ring the LC network With the inductance and capaci tance values specified in Fig 1 the Square wave pud Gimmick generator Low capacitance proba Oscilloscope LC network will ring at approximate ly 1 MHz The scope will display a ringing waveform like that shown in Fig 2 If L has considerable distri buted capacitance the effective total capacitance in shunt to L will be sig nificantly greater The result will be that the network will ring at a lower frequency as low as 0 5 MHz As illustrated in Fig 2 B this bas ic ringing waveform has a decaying damped sine wave shape and the damping is expone
104. and write 5 or F next to the mark to indicate if the clock ran slow or fast at that setting This will give you an idea of how much rotation is needed for a given change in speed After a few reset tings you will notice the marks zero ing in on a point that has slow settings marked on one side and fast settings on another side Once the Tide Clock is calibrated it can be set to the current tide by con sulting a chart check your daily newspaper After making this initial setting you can dispense with the need for the chart unless the project should lose power for a prolonged period of time and where exact times are needed Even if you built this project to serve primarily as a Tide Clock do not overlook its other uses Away from home it can be used as a low power inverter for equipment that does not require a true sine wave as the drive signal At home the main application for this project will be its use as a means for changing the speed of synchronous motors WWW americanradiohistorv com tances being used to get closer to the mark In addition if you wish to in crease the timing intervals you can increase the resistances of the timing resistors All timing tests should be made from a start Let the timer rest for 5 minutes between checks of each range selected by the DIP switch To put the project into service you simply select the desired snooze inter val
105. another tele phone may prevent the answering phone via a Touch Tone DTMF machine from recognizing the proper or compatible telephone keypad in Cantinued on page 72 Microphone Analog to digital converter ADC ANALOG Micropho ne INPUT amplifier DIGITAL OUTPUT ENABLE ty SAMPLE CLOCK DONE EEPROM DATA ADDRESS Speech i Timer RECORD OGM data storage counter Main pP and 5 Start 10110101 circuit central cit uit record STROBE RECORD DONE 10001100 211011001 Fig 8 One possible approach for assembling a voice digitizer recorder 24 MODERN ELECTRONICS March 1990 Say You Saw It In Modern Electronics WWW americanraciohistorv com Project Dual Polarity Power Supply This project offers a dual polarity power source that is adjustable from 1 2 to 37 volts and a built in digital numeric metering system By Tim Swogger odern electronic circuits often require a variety of voltages and two polari ties The Dual Polarity Power Sup ply described here fulfills the needs of virtually all solid state circuits you are likely to encounter or build It of fers a wide range of adjustable out put voltage at moderate current The design of the circuitry gives you a choice of adjustment ranges from a low of 1 2 volts to a high of 24 or 37 volts depending on the power trans former selected As a bonus t
106. beep that the caller hears Everything the caller says is then heard over the machine s speak er and passed to the ICM recording head to be placed on the ICM tape Fig 4 This is what makes Call Screening possible The type of cassette tape used de pends on the design of the individual answering machine Some machines use one or two standard size audio cassettes similar to those used in home and car stereos others make Caller hears Hello you have reached T Telephone coupling and switching circuit R Pickup Pickup Circuit Main and control circuit Hello you have reached gt OGM 7 Head amplifier Drive motor Motor drive OGM message done sensor Fig 3 When outgoing message is finished Control circuit stops play and switches in incoming message record head use of one or two microcassettes to store the OGM and ICMs Regard less of which size cassette is used the operation of the answering machines is the same The ICM cycle continues until the selected message duration times out A variety of time selections are used in telephone answering machines There are usually a short fixed time of 1 minute or less a long fixed time of 2 minutes or more and a VOX voice activated selections The VOX causes the machine to record an ICM for as long as the caller speaks with no time limit If the caller stops speaking for a few seconds the VOX
107. bout 0 7 volt for every diode used March 1990 MODERN ELECTRONICS 33 a WWMW americanradiohistorv com PARTS LIST Semiconductors D1 D2 D3 1N4001 or any other sili con rectifier diode D4 D5 D6 50 volt 3 ampere or more silicon rectifier diode IC1 7812 12 volt 3 terminal vo tage regulator IC2 XR 2206CP function generator Exar Corp IC3 1C4 4049 hex inverter LED1 Red panel mount light emit ting diode Q1 Q2 2N3055 npn power transistor in TO 3 case Capacitors C1 220 pF 16 volt electrolytic 2 1 10 or better tolerance non polarized Mylar propylene or poly styrene C3 10 4F 16 volt electrolytic 4 400 volt or better nonpolar ized C5 1 000 4F 16 volt electrolytic Resistors 14 watt 5 tolerance R1 16 000 ohms R2 R3 R4 10 000 ohms 5 220 ohms R6 R7 150 ohms R8 2 000 ohm multi turn pc mount trimmer potentiometer Miscellaneous F1 3 ampere slow blow fuse I1 Panel mount neon lamp assembly with current limiting resistor J1 J2 Panel mount banana jack Si 3 ampere or better dpdt toggle switch SO1 Panel mount ac receptacle T1 T2 24 volt center tapped 2 am pere power transformer TS1 Two position panel mount screw type terminal strip Synchronous motor analog clock see text printed circuit board or perforated board with holes on 0 1 inch centers and suitable Wire Wrap or soldering hardware see text suit able enclosur
108. car ries the data from the other modem Al though the two signals clash and interfere with each other the method works be cause your modem knows what it is send ing All you do is subtract your signal from the total to hear what the other mo dem is saying This is done by creating an inverted sig nal of your modem s output using an op erational amplifier and feeding it to your receiver s input When the transmitter s output voltage goes positive the receiv er sinput voltage goes negative resulting in a zero voltage at the input of the receiv RA TATUR C C a ZH E Ae 54 MODERN ELECTRONICS March 1990 Say You Saw It In Modern Electronics WWW americanradiohistorv com er for that signal Once your signal is can celed all that remains is signal coming from the other modem Data Compression The other half of the Racal Vadic Model 9632VP success story is built in MNP Class 5 data compression Data compres sion doesn t change the way the modem works only the way the data is packaged before it is sent MNP 5 has a 2 to 1 data compression ratio which allows the Mod el 9632VP to communicate at 19 200 bps MNP 5 data compression created and licensed by Microcom works by looking for repeated characters or patterns in the data string such as spaces or tabs in a ta ble and replacing them with unique con trol characters It also counts the number of times a character appears in a docu ment like the letter
109. clock face is ready simply mount the motor mechanism to it usually with small wood screws Mount the motor to the clock face in any manner that works for you If you are making a large size Tide Clock display as shown in the photo of the prototype the hours hand you removed from the clock mechanism is usually too small to be of use Mak ing a new hand is usually necessary in a case like this However give some thought to the material you will use This must be light in weight to pre vent loading down the clock motor A thin piece of sheet plastic brass or even balsa wood should work well here Other materials may come to mind as well A car stereo knob is a good way to Say You Saw It In Modern Electronics mount the new hand to the motor s shaft An alternative is to use a small cork with a hole of the correct diame ter drilled in it Although the clock motor shaft will have two to four concentric shafts that different hands were once attached to only the shaft that formerly held the hours hand is to be used in this project For tunately the shaft for the hours hand is usually the largest in diameter and most accessible since it is the outer most of the group except for the re movable alarm shaft that 15 featured on some clocks Checkout amp Calibration Before attempting to calibrate or put into service your Tide Clock it is a good idea to check out voltage distri bution throughout the system to make sure
110. coincident with the RD input edge The start of conversion resets the internal successive approximation regis ter SAR to 0000 0000 0000 and enables the three state outputs The BUSY line is active low during the conversion process During conversion the SAR sequences the voltage output DAC from the most significant bit MSB to the least signifi cant bit LSB In other words it succes sively tests each bit to see if it should re main at zero or be changed to 1 The ana log input A which can vary between 0 and 10 V for this device connects to the comparator via a 5 k ohm resistor The DAC which has a 2 5 k ohm resistance connects to the same comparator input AGND VYrer N 3 2 912 12 SUCCESSIVE APPROXIMATION REGISTER 12 BIT LATCH gt B MULTIPLEXER 8 THREE STATE OUTPUT DRIVERS THREE STATE OUTPUT DRIVERS 13 D Doz CONTROL LOGIC CLOCK 18 O CLK OUT OSCILLATOR qv C CLK IN Fig 1 Precision Monolithics ADC 912 A D converter offers successive approximation conversion as shown in Fig 2 Notice that the DAC voltage can vary over a range between 0 and 5 V Vggr The first test occurs for the number 1000 0000 0000 which makes the DAC voltage 2 5 V Ananalog input of 6 3 V would cause a positive potential of 0 4 V to appear atthe positiveinput to the com parator Since the negative input of the compa
111. ctrum Probe Figure 6 A shows the signal from the transmitter as displayed on an oscillo scope screen when the Spectrum Probe was located about 1 foot or so away To avoid interfering signals from local radio stations the Spectrum Probe was not connected to an antenna The digital fre quency readout of a communications re ceiver indicated that the transmitter sig nal peaked at 84 MHz The half power points of the signal were located at 83 3 and 84 1 MHz The signal shown in Fig 6 A was ob tained when the clip lead tapped the coil at its center point Fig 6 B is a triple ex posure scope photo that shows how the Loo QL 2 5 0 ANTENNA STIFF WIRE Li S TURNS TAP AT 1 1 2 TURNS LL x 28 45 I 4 2 Fig 5 Four turn oscillator coil for Fig 4 circuit showing center tap clip lead frequency can be altered by moving the position of the tap Moving the center tap one turn toward the antenna end of the coil raised the frequency to 93 75 MHz Moving it one turn toward the ground end of the coil dropped the frequency to 76 4 MHz These three frequencies are clearly displayed in Fig 6 B To make this photo I simply moved the clip lead to the three points on the coil mentioned above and made an exposure of the screen each time March 1990 MODERN ELECTRONICS 63 Say You Saw It In Modern Electronics JAMMWeamerdcanancsasciobistoenmcconm
112. d 4 99985 Stephen J Bigelow Kudos and Corrections really enjoyed the two part article Microprocessor Control With BASIC in the April and May 1989 issues In fact it was because of this series that I decided If you ve been looking high and low for a dependable supplier of top quality electronic parts and components let MCM end your search LOOK OUR QUALITY it s tough to beat LOOK AT OUR SELECTION over 15 000 in stock items to choose from LOOK AT OUR VALUE some of the most competitive prices in the industry LOOK AT OUR SERVICE convenient TOLL FREE phone lines fast order turnaround and courteous friendly assist ance when you need it If these are the things you ve been looking for it s time you look to MCM ELECTRONICS The first time you do you ll like what you see cm om rm oim 1214 Ip A emi OE Qum io camem n Tito cates jd 22 ir ELS gt em aee For a FREE ONE YEAR 7 SUBSCRIPTION to the RA a Electronics HEP RE Call TOLL FREE E 1 800 543 4330 Say You Saw It In Modern Electronics CIRCLE NO 142 ON FREE INFORMATION CARD to subscribe to Modern Electronics Please keep this kind of article coming and thanks for a good magazine While building the project presented in the April issue I noted a few errors in the schematics Fig 1 for IC3 pin 16 not pin 14 as shown connects to 5 volts
113. d 6 The signal on pin 2 is gener ated by C5 operating as 1 of 6 de coder demultimplexer When this signal is high the pins 3 through 6 outputs are in high impedance state Thus all flip flop outputs can be connected to a common bus feeding the inputs of Power for the project is supplied by a suitable 5 volt dc power supply If you do not have one handy you can build the one shown schematical ly in Fig 4 This is a common full wave supply with built in voltage regulation provided by 12 Construction You can assemble this project using any of a number of traditional wiring techniques If you wish for exam ple you can design and fabricate a printed circuit board on which to mount and wire together the various 40 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com PARTS LIST Semicondactors D1 thru D4 1N4003 or similar silicon rectifier diode DISP1 thru DISP6 Common cathode LED numeric displays to mount in 14 pin DIP socket IC1 74C917 six digit hex display controller driver IC2 CD4049 hex inverting buffer IC3 74LS00 quad two input NAND gate IC4 74LS390 dual decade ripple counter ICS 74L8138 1 of 8 decoder ultiplexer IC6 thru C1 1 74LS173 Quad D type flip flop with three state outputs IC12 7805 5 volt regulator Q1 thru Q 2N3904 or similar silicon npn transistor Capacitors C1 47 pF ceramic disc 2 0 1 ceramic disc C3 2 500 4F 16
114. ded signal for monitoring with a logic probe The most accurate reading ob tained is with an accurately cali brated frequency counter Of slight ly lesser accuracy is scope monitor ing while use of a logic probe simply gives an indication of signal activity f you obtain any signal activity re gardless of which monitoring meth od you employ you can assume that the clock oscillator is working Having verified that the clock os cillator is working pull the project s line cord from the ac receptacle al low the charges to bleed off the filter capacitors in the power supply and then install a 74LS390 in the 4 socket and 741 500 into the C3 socket Again make sure the pins of the ICs and all subsequent ICs and LED numeric displays engage the socket pins Connect separate light emitting diodes through 330 ohm current limiting resistors to the outputs of IC4 at pins 2 5 7 10 11 and 13 The cathodes of the LEDs go to the speci fied pins on the IC while the anodes go to the 5 volt bus through the current limiting resistors Leave the CD4060 still connected to the project as described above Then temporarily connect one of the slow outputs see Table in Fig 5 to input pins 1 and 15 of 7C4 Power up the project and observe the LEDs for activity If you selected a low enough frequency out of the CD4060 you should observe the LEDs flashing on and off to show the BCD count Having verified that both counters i
115. deo drum cylinder Many more aspects of VCR repair UCANDO totheinternal comparator This problem can be minimized by forcing the micro processor into a WAIT state during con version alternate method is isolation of the data bus with three state buffers such as the 74H C541 A D Converter Selection Precision Monolithics ADC 912 is a low noise precision 12 bit high speed CMOS A D converter A major objec tive in designing the ADC 912 was to re duce transition noise Some 12 bit Mail check or money order to DER or call us at 513 548 6113 P O BOX 386 OR VISA and MASTERCARD accepted GREENVILLE OHIO 45331 BE A SUCCESS WITH UCANDO VIDEOS CIRCLE NO 118 ON FREE INFORMATION CARD 66 MODERN ELECTRONICS March 1990 Say You Saw It In Modern Electronics A WWwW americanradiohlstorv com Laten 0 65 Lat Multiplexer l1 T 7 National Semiconductor DGND AGND Fig 3 National Semiconductor s ADCO080xx A D converter series include on board ref Controi and Tinmng Output Shift Register 25V Band Gap Reference Veer IN Qut erence multiplexer and track and hold functions CMOS A D converters exhibit 1 4 to LSB of transition noise which is often misinterpreted by users of this device as a circuit layout problem The ADC 912 is designed with a low noise comparator that results in A D converter operation that is
116. distance of about 3 inches Strip inch of insu lation from the ends of all cut end conductors tightly twist together the exposed fine wires in each case and sparingly tin with solder Use heat judiciously to minimize charring the insulation Pass the unprepared ends of tne cables through the narrow slots you cut through the rear panel from the inside of the enclosure Plug the headers at the ends of the cables into the J and J2 IC sockets Leaving about 1 inch of slack in each cable in side the enclosure apply a liberal bead of silicone adhesive on both sides of the cables to secure them in place against the rear panel Allow the adhesive to fully cure at least overnight before proceeding When the adhesive has cured ter minate the unfinished ends of the conductors in suitable connectors for your expected applications System Checkout If you incorporated the POWER switch and fuse into your project place a fuse into its holder Clip the common lead of a dc voltmeter or a multimeter set to the dc volts func tion and set the meter s range selec tor to a position that will easily dis play 5 volts Bear in mind that no ICs except regulator 1 2 in the power supply or LED numeric displays should be plugged into the sockets on the circuit board assembly for pre liminary voltage tests Plug the line cord of the project in to an ac outlet As you perform volt age checks with the meter make ab solutely certain t
117. dy the efficiencies of vari ous kinds of antennas and antenna ter minations Simultaneous signals transmitted by two CB transceivers are shown in Fig 3 A One transceiver transmitted at a frequency near 27 MHz the other on a frequency near 49 MHz Figure 3 B shows the simultaneous signals received by the Spectrum Probe when a cordless telephone is being oper ated The two separate signals are re quired so that full duplex communica tion can take place Figure 3 C is particularly interesting because it shows the rash of r f noise spikes that are generated by a small dc motor This screen photo reveals a sharp drop in the amplitudes of noise spikes just beyond the midpoint of the display at around 55 MHz Nevertheless there s still plenty of noise out to and presum ably beyond the 100 MHz limit of the display Similar noise spikes are pro duced when mechanical switches and re lay contacts are opened and closed in a circuit in which a current is flowing It s possible to expand the Spectrum Probe display by means of the oscillo scope s horizontal sweep controls espe cially the 10 multiplier and delayed sweep controls For example Fig 3 D shows an expanded view of the index marker and several AM broadcast band radio signals In Fig 3 E the sweep is further expanded to show a magnified March 1990 MODERN ELECTRONICS 61 Say You Saw It In Modern Electronics WWW americanradiohistorv com Rm
118. e ac power supply charger and a connec tor for the available external disk drives These external drives are 5 25 inch units and are offered in either 360 KB or 1 2 MB capacities The Compaq 286 L TE is more impor tant for what it represents than what it is Except for its small size it functions al most exactly the same as my desktop Compaq It does this while being small enough to fit in an attache case This amount of power presently carries a hef ty price tag At almost 6 500 as config ured for this review the Compaq 286 LTE is more expensive than many 386 desktops If you don t need all of the power that this model offers the 8086 based LTE with a single floppy and no hard disk costs considerably less at 2 399 It s also almost a pound lighter at 6 pounds versus 6 7 pounds for the 286 1 Yet the last decade shows us that where there is a need eventually the market will meet it at a reasonable price Standard size laptops can now be pur chased for less than 1 000 Notebook sized PCs such as the Compaq LTE and 286 LTE make even more sense to many of us who need portable computing pow er Given the ready availability of lunchbox clones of Compaq s Por table II and Portable III it wouldn t sur prise me much if next year there were a whole slew of affordable notebooks Whether these are disk based systems like the LTE or RAM based ones like the NEC UltraLite doesn t make much dif ference to me I only
119. e see text solder lug type terminal strip sockets for all DIP ICs fuse holder materials for making clock face see text small diameter heat shrinkable tubing suit able machine hardware hookup wire solder etc The diodes used in this circuit assure that the power supply voltage for the ICs is at least 12 volts dc even for a slightly out of specification regula tor IC If desired D and D2 can be eliminated Construction Most of the construction work for this project is entailed in wiring the Fig 2 circuit and housing it in a suit able enclosure What remains after that is taking apart an existing ac line powered analog clock to salvage the drive motor and fabricating a new face and hand to match its new function as a tide clock Owing to the fact that only low frequency digital level signals are used in this project you can wire the Fig 2 circuit on either a printed cir cuit board or perforated board that has holes on O 1 inch centers using suitable Wire Wrap or soldering hardware A final alternative is to wire together the components on a Universal PC Board like the Radio Shack Cat No 276 168 If you opt for printed circuit con struction you can fabricate a suit able board using the actual size etch ing and drilling guide shown in Fig 3 From here on we will assume pc construction Once the board is ready to be populated orient it as shownin Fig 4 Begin wiring it by in stalling and solder
120. e wires in each line cord conductor and sparingly tin with solder Crimp and solder one line cord conductor to one lug of the terminal strip and solder the primary lead of the trans former already in place on this lug Mount the fuse holder and POWER switch if you are using them in their holes on the front panel Connect and solder a suitable length of hook up wire from one lug of the switch to one lug of the fuse holder Similarly connect and solder a hookup wire to the other lug of the fuse holder route the other end to the unsoldered lug of the terminal strip Crimp the free end of this wire to the lug and solder it and the primary lead already occupy ing the same lug Then separate the line cord conductors inside the enclo sure to within inch of the strain re lieving knot Crimp and solder the unattached conductor to the unoccu pied lug of the POWER switch The input cables for the project consist of standard 16 conductor ribbon cable assemblies terminated in 16 pin DIP headers Two separate input cables are needed Cut off and discard one header from each cable a r 2 CL iil To eU ICE Mcr Saw it In Modern Electronics March 1990 MODERN ELECTRONICS 43 TI Vac Fig 4 Schematic diagram of a suggested 5 volt regulated dc power supply for 01 04 IN4003 use with project Then carefully separate the conduc tors at the cut ends a
121. e coil was center tapped and when a 1 foot long antenna was connect ed to the Spectrum Probe Note that the amplitude of the transmitted signal was nearly 40 dB greater than that of the strongest signal from nearby TV and FM broadcast stations Figure 6 D is an expanded view of the signal from the transmitter when it was center tapped This photo shows some undesirable spurious oscillations With the Spectrum Probe in opera tion you can instantly see the results of adjustments to the transmitter Place a finger next to the coil and observe what happens Then try squeezing and stretch ing the coil in the transmitter Another interesting experiment you can perform is to replace C5 in Fig 4 with a variable capacitor and R6 and R7 with a poten tiometer as described above Changing the settings of these two adjustable com ponents will produce significant changes in oscillation frequency Summing Up The Spectrum Probe represents a major breakthrough for low cost r f spectrum analysis While it doesn t possess many of the refinements and features of more sophisticated spectrum analyzers its sen sitivity bandwidth and compact size make it a test instrument that s well worth its reasonable cost 64 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com Say You Saw It In Modern Electronics SOLID STATE DEVICES mE Analog to Digital Converters By Joseph Desposito Many applications require that a
122. e of an input signal and B showing ambient r f signals received with a short wire antenna come from specific stations This pro vides a convenient means of comparison of the relative signal levels of the stations at your location Though Fig 2 B shows the signals re ceived by the Spectrum Probe when a short wire is attached to its input you can obtain a very similar result simply by touching the Probe s input with a finger This provides a convincing demonstra tion of the ability of your body to func tion as an r f antenna Experimenting With The Spectrum Probe I ve learned a good deal about the r f sig nals in my office with the help of the Spectrum Probe What follows is a sum mary of some of the many measurements and experiments you can conduct with this versatile instrument You use the Spectrum Probe much like a conventional oscilloscope probe to trace various kinds of circuits For exam ple you can inspect digital circuits that have clock speeds in excess of 1 MHz As pointed out in literature from the manu facturer of the Spectrum Probe the har monics that may be present on a digital line can be rather surprising The probe is especially useful for trac ing the r f sections of radio transmitters Since the input of the probe has a very low capacity it has little effect on the cir cuit being monitored The probe can also be used to optimize the lengths of anten nas and to stu
123. e of their small size answering machines perform a remarkable va riety of functions to accomplish their task A complete block diagram of a simple answering machine is shown in Fig 1 which details each major function area and identifies it with a 18 MODERN ELECTRONICS March 1990 WWW americanradiohbistorn corm key number Let us look at each of these areas in turn 1 Telephone Switching amp Coupling Circuit This part of the system is run by the control circuit It draws the current required to pick up a ringing telephone circuit and switches the audio path as needed into and out of the machine It also switches the mi i Say You Saw It In Modern Electronics e crophone and speaker as needed 2 Main Microprocessor amp Control Circuit This is the heart of the sys tem in terms of controlling opera tions It controls the switching ac tions of the coupling circuit inter prets the panel controls and directs enable signals to the motor mechan isms and record play heads It also handles the machine s security code when used with a remote control unit 3 Ring Detector Counter This portion of the system senses the pres ence of a valid ring signal from the telephone line and converts it into a series of logic pulses Each pulse is counted until the appropriate num ber of rings is reached at which time an enable signal is generated to the pickup circuit A ring selector switch det
124. east 3 books wi hin the next 12 months and may resign at any time thereafter Ironclad Guaran tee If not satisfied with your books return them within 10 days without obliga tion Exceptional Quality All books are quality publishers editions especially selected by our Editorial Board 2960 27 95 1990 ELECTRONICS BOOK CLUB Blue Ridge Summit PA 17294 0810 All books are hardcover unless number is followed by a P tor paperback Publishers Prices Shown FREE when you join 15 Easy Electronic Projects From Delton T Horn Projects you can build some unique some old favorites from the author s vast treasury of electronics know how Ecectagnics Li Blue Ridge Summit PA 17294 0810 Please accept my membership in the Electronics Book Club and send the 5 volumes listed below plus my FREE of Delton T Horn s All Time Favorite Electronic Projects 3105P billing me 4 95 plus shipping and handling charges If not satisfied may return the books within ten days without obligation and have my membership cancelled agree to purchase at least 3 books at regular Club prices plus shipping handling during the next 12 months and may resign any time thereafter Counts as 2 A All Time Favorite Value 2707 526 95 Counts as 2 PRACTICAL ELECTRONIC CIRCUITS Beyond the Transistor UDO Hectrenics Prajects 2887 16 95
125. ecember as I m writing it And I ve just returned from another one of the computer industry s bi annual circuses C COMDEX This was the larg est yet 120 000 attendees and 1 740 ex hibitors Needless to say I didn t get to see all of them The big news this time out was the number of 1486 machines being shown Almost every major vendor of PCs was showing one and quite a number of un known vendors had one too This was especially interesting as few companies can actually deliver There is an acute shortage of the i486 CPU chips and quite a number of those already delivered have a problem with certain floating point operations Intel is in the process of swapping out these flawed chips which should further slow down shipment of the 1486 PCs Nevertheless the quick embracing of this CPU means that prices on 486 sys tems should fall much more rapidly than they did with its predecessor the 80386 While I am skeptical that very many users actually need the power of this CPU it doesn t really matter All users myself included want the most powerful PC they can get whether or not they will ever put this power to full use Even with fall ing prices though the 1486 will be out of the range of affordability for many of us for some time to come The other interesting trend I noticed is towards smaller lighter and some times more affordable laptops couple of columns ago I provided a quick look at the Atari Portfoli
126. echnology behin Robotics Basic Electronics C Travel Careers both digitized and synthesized com E ED ae Bookkeeping amp Accounting C Writing te h D Security Electronics Building Construction O Paralegal puter speech O Digital Electronics Servicing Automotive Servicing Computer Programming NRI s new hands on training in voice synthesis is just one more way ii MR Age you get the confidence building experience you need to feel at home a _ with the latest advances in computer City State Zip We ll give you tomorrow Accredited Member National Home Study Council 4 030 WMWMM americanradiohistory com For more information on products described please circle the appropri ate number on the Free Information Card bound into this issue or write to the manufacturer Cordless Soldering Iron Black amp Decker s new Model 9768 cordless soldering iron with tip re placement capability is powered by butane gas The fast heating Therma Cell butane power cartridge rated to give more than 2 hours of opera tion is ignited by a piezoelectric starter for instant start up without flints or a battery Tip temperature is said to reach 650 degrees in less than 2 minutes The 3 5 ounce iron fea tures a built in stand CIRCLE 51 ON FREE INFORMATION CARD Power Supplies New from Beckman
127. ed board Measur ing 6 x 4 inches the Radio Shack Cat No 276 147 has a copper pad for each hole on the wiring side of the board You can use this or any other similar board or even perforated board that has no pads around the holes if you go this route To provide stability assuming pad hole board and the point to point wiring tech nique it is suggested that you solder at least the corner pins of each IC socket to the pads surrounding them Begin construction by installing the IC and display sockets Also mount into place between the edge of the board and the six sockets for through 16 DIP sockets J7 and J2 shown unoccupied in the lead photo If you are using a pc board or pad hole perforated board solder the pins of the sockets into place If you are point to point wir ing the circuit it is a good idea to mark the pin 1 position for each socket on the wiring side of the board Alternatively you can place commercial plastic ID label on which the pin numbers are printed for each socket location Do not plug any ICs or displays into the sockets until after you have performed initial voltage checks and are certain that all wiring 1s correct Again assuming you are using a pc board or pad hole perforated board install the resistors and then the capacitors in their respective loca tions and solder both leads of each into place Having come this far you are ready to proceed with wiring together the
128. electronics career that will challenge and excite you every day reward you with a powerful feeling of personal accomplishment and deliver a level of financial security may have only dreamed of before As the leading school in home study electronics CIE has helped over 150 000 students in the U S A and over 70 foreign countries get started in this exciting field To find out how CIE ceuld be helping you read on then send for a CIE catalog TODAY A Growing Need For Trained Professionals The career opportunities shown here are only a few of the challenging high paying careers you could enjoy as an eiectronics technician You could be the brains behind the scenes of an exciting TV broadcast trouble shoot life saving medical equip ment design exotic new aeronautics systems CIE s job oriented programs affer you the quickest possible path to the career of your dreams And CIE also features military and union re training to build on what you already know Dozens Of Fascinating Careers To Choose From Even if you aren t sure which career is best for you CIE can get you started with core lessons applicable to a areas of electronics As you advance CIE makes job opportunities available to you through the bimonthly school paper The Electron Military Flectronics Personal Training From Renowned Faculty Unlike the impersonal approach of large class room study CIE offers you one on one
129. er nal 2 400 baud modem This configura tion is a very usable one and carries a fairly hefty price tag 6 247 TheLTE which is missing only the let ter i to spell lite is supposed to in a certain image in your mind one that suggests ease of transporting At be tween 6 and 7 pounds depending on which model you choose and its small size the image is a fairly true one Very little however is sacrificed in the way of usability to provide this portabili ty The LTE contains a battery that pro vides up to 3 5 hours of use a very read able backlit LCD screen and an 80 key keyboard This keyboard has keys that are just slightly smaller than those on a standard keyboard and an embedded keypad I found it to be as usable as those found on most laptops If you do much numeric work though you will almost definitely want to purchase the optional external numeric keypad The Control and Alt keys are also a bit awkward to use There are two of each located on the left and right of the space bar Once you get used to their locations you can find these keys fairly easily But until you do it s easy to hit the wrong keys by mistake LTEs also have an extra key labeled in thelower left corner of the key board This key is used to access function keys Fil and F12 physically located on the F1 and F2 keys as well as the cursor Se T 68 MODERN
130. er in computer technology supply and 51 4 disk drive then interface the high resolu i ANN tion monjtor But that s not all Train With a Powerful Your hands on training ible N continues as you install a mpatible Now powerful 20 megabyte hard with 20 Meg Hard disk di qu a Un wanted computer peripheral Drive and Meg now included in your course to RAM dramatically increase the data storage s cd of yan cy To give you hands on training dit tio diea puter while giving you light with the absolute in state of NIMM TAE i si a ning quick data access Plus the art computer technology 2 UU n you work with exclusive word NRI includes the powe Tots processing database and West Coast 1010 ES computer spreacsheet software yours to as the centerpiece of your use for your own professional training As you assemble this EET TCR SC aera Edo E personal applications fully IBM AT compatible all the while gaining a true mastery of computer As you build your com micro from the key on electaonics Best of all it s yours to keep for all your puter performing key demon up you actually see for professional and personal computing needs strations and experiments at yourself how every section of each stage of assembly you get your computer works Secret teri im So 7 the confidence building real WWW americanradiohistorv com Your NRI c
131. er see text T2 6 3 volt power transformer Printed circuit board or perforated board with holes on 0 1 inch centers and suitable Wire Wrap or soldering hardware see text suitable enclosure a 5 9 x 5 3 x 3 0 metal instru ment case is suitable for basic power supply circuitry if you add optional 5 volt power supply select a larger en closure see text DIP IC sockets control knobs for R11 and R12 holder for F1 ac line cord with plug small rubber grommets for mounting LEDs rubber grommet for line cord entry hole small diameter heat shrinkable or other insulated tubing dry trans fer lettering kit clear spray acrylic machine hardware hookup wire sol der etc while bypass capacitors C5 and C6 provide noise immunity on the two output voltage lines A separate power supply is pro vided for powering the metering dis play circuitry This supply is com posed of power transformer 72 the bridge rectifier assembly made up of diodes D5 through D8 again the discrete rectifier diodes can be re placed with an integrated bridge rec tifier assembly filter capacitor C8 and fixed 5 volt voltage regulator IC3 The regulated output of this supply is distributed throughout the remainder of the circuitry Voltages fed to the pin 11 input of three digit dual slope A D convert er ICS This IC converts the analog voltage into a digital BCD equivalent at output pins 1 2 15 and 16 These outputs are directly coup
132. ermines the number of rings counted before the machine picks up 4 Pickup Circuit Activated by the E ring counter this circuit tells the con trol circuit that an incoming call is waiting and to pick uptheline and ex ecute the outgoing message OGM sequence 5 Message Duration Timer This is activated when theincoming message ICM sequence begins It tells the machine to disconnect when its pre set timer runs out Timer duration is determined by the setting of the mes sage duration timer switch 6 Security Code Switches These re strict access to the answering ma chine to only the remote controller that has the matching security code number or a dialpad code that a beeperless remote machine recog nizes These switches can be fixed in to the machine or changeable inside 7 Panel Controls These consist of the PLAY REWIND FAST FORWARD and MEMO buttons on the front pan EiPcrHONICS March 1990 el Other controls can also be pres ent depending on the particular fea tures of the machine This area also contains the controls for recording and reviewing the OGM and any in dicators and displays 8 Motor Speed amp Direction Con trols These determine whether the ICM or OGM tape moves if it is a two tape system along with that tape s speed and direction Though only one motor is used in most ma chines gears and solenoids switch the motor s force and direction to the mechanism t
133. es as a buffer between C3 and Say You Saw It In Modern Electronics the two transistors Note that there are two groups of three inverters con nected in parallel in C4 one for each transistor to provide enough current to bias the transistors into saturation As QI and Q2 alternately conduct each allows current to flow in alter nating directions through the secon dary of transformer 77 Capacitor C4 suppresses switching transients and the neon lamp provides visual indication when power is being deliv ered to ac OUTLET SO into which the Tide Clock s display or other syn chronous motor is plugged The ac dc driven power source shown schematically at the lower left in Fig 2 is of conventional design It permits operation from either a 12 volt dc or 117 volt ac source A single double pole double throw switch 51 is provided for powering the project from the ac line and to switch between ac and dc modes The power supply provides a 60 Hz pulse train that is used to derive the beat frequency discussed above During operation from a 12 volt dc source the beat frequency display does not operate and LED simply remains dark Although the power supply drives the inverter section of the main cir cuit directly it passes through volt age regulator before powering the more delicate timing and switch ing ICs Using D and D2 in the re turn path of regulator C7 as shown increases the output of the chip by a
134. essional instruments Nevertheless in many applications the Spectrum Probe does provide a usable substitute for considerably more expen sive instruments The Spectrum Probe is easy to use Its male BNC connector goes to the input of the oscilloscope and its plug in wall transformer connects to a source of 117 volt ac household current The oscillo scope is then initialized Horizontal sweep is set to 0 5 millisecond per divi sion to give a frequency response of about 10 MHz per division and total fre quency range of 1 MHz to slightly be yond 100 MHz The vertical scale is then set to 50 millivolts per division to give a sensitivity of 16 decibels per vertical divi Say You Saw In Modern Electronics sion for a total dynamic range of more than 50 dB Logarithmic linearity of the vertical scale is 3 dB Shown in Fig 2 A is a typical oscillo scope display produced when the Spec trum Probe is operated in my rural office in South Texas without the presence of any incoming r f signals In operation the oscilloscope trace is adjusted to be near the bottom of the screen The verti cal spike shown at the extreme left side of the sweep is a zero marker that indicates the beginning of the sweep at about 1 MHz Just to the immediate left of the zero spike is a negative synchronizing pulse The next arrival of this pulse is sometimes visible on the extreme right end of the trace Figure 2 B shows the display when a short cl
135. etwork The tuned transformer is ringing at two slightly different frequencies and the ringing pattern is a beat resultant of two decaying sine waves that have slightly different frequencies Say You Saw I In Modern Electronics Current A B Time ps Fig 2 Example of a ringing waveform with exponential decay A is the pattern of the waveform as it would appear on the screen of an oscilloscope B is the graphed plot of the waveform parameters versus time Lp L 0 15 mH M C C 169upF 26 k 0 01 Q Q 100 90 5 80 1V L j 70 A 60 k 0 03 E 50 E 0 002 gt e E 1 a t 5 e gt ei o o e 0940 960 980 1000 1020 1040 1060 0940 960 980 1000 1020 1040 1060 B Time ps C Time ys Fig 3 Details of an AM i f transformer A Thevenin representation B plots of primary signal current flow of three degrees of coupling C plots of secondary current flow of three degrees of coupling Say You Saw It In Modern Electronics March 1990 MODERN ELECTRONICS 47 RI m m a GU M cU UR S c c a u a S S 00 Le cmm d A Secondary current B Frequency 7 Fig 4 Example ofa ringing waveform for a tuned i f transformer illustrating the effect of two ringing frequencies as it would appear on the screen of
136. gged edges This is caused by the copy protec tion jamming signals em bedded in the video tape such as Macrovision copy protection DIGITAL VIDEO STABILIZER RXII complete ly eliminates all copy protec tions and jamming signals and brings you crystal clear pictures WARNING The Digital Video Stabilizer RXII is in tended for private home use only It is not intended to copy rental movies or copyrighted video tapes that may constitute copyright infringement eee m m oq o m m m Rm Rm m ee FEATURES Easyto use and a snap to install The best and the most exciting Video Stabilizer in the market State of the art micro chip technology 100 automatic no need for any troublesome adjust ments Works on aif types of VCRs TVs and Monitors e Light weight 8 ounces and Compact 1 3 5 5 Beautiful deluxe gift box Uses a standard 9 Volt battery which will last 1 2 years Similar units sold eise where for 99 or more UNCONDITIONAL 30 DAYS MONEY BACK GUARANTEE FAST UPS DELIVERY Air Shipping available ir ToOrder 1 800 445 9285 or 516 568 9850 49 95 4 Visa COD M F 9 6 battery not included Electronics Inc SCO Dept CAR 581 W Merrick Rd Valley Stream NY 11580 CIRCLE NO 137 ON FREE
137. gital numeric me tering systems for simultaneous viewing of output voltage and cur rent and current limiting reverse polarity protection and isolated out puts Range adjustment is provided by separate COARSE and FINE con trols on the front panel Also on the front panel is a control for setting output current 395 Model MPS60 425 Model 5100 CIRCLE 53 ON FREE INFORMATION CARD Remote Controlled Thermostat Set Back New from X 10 USA Inc is the Model TH2807 X 10 Powerhouse Thermostat Set Back for remote control of set back at preset times for central heating and air condition ing It automatically tells the ther mostat with which it is used to initi ate set back when the user retires for the night and then prompts the ther mostat to restore the home to a com fortable level in the morning The unit works with any kind of thermo stat low voltage 117 volt pneu matic or otherwise No wiring to the existing thermostat is required dur ing installation Instead the unit at taches to the wall just below the ex isting thermostat where it supplies a small amount of local heat to fool the thermostat The unit plugs into the ac line through an appliance module and is operated from an X 10 remote control unit timer tele phone responder etc 19 99 CIRCLE 54 ON FREE INFORMATION CARD Say You Saw It In Modern Electronics A V Disc Player Said to be the industry s first 5 in 1 aud
138. h a new one Now that you have tested all the subsystems in your project and cor rected any wiring errors you have de tected during this operation it is time to connect the output of the clock generator to the first counter With power turned off and no charges on the filter capacitors in the power supply install the 74C917 chip in the C socket employing the same precautions you would use for handling any other MOS type device Power up the project and check operation of the complete system Change the BCD inputs to flip flops IC6 through and verify that the LED numeric displays show the cor responding hex signals To use the project simply clip the leads of its input cables to the appro priate points in the circuit under test Power up the circuit being tested and the project and observe the numeric displays That is all there 15 to it March 1990 MODERN ELECTRONICS 45 Say You Saw It In Modern Electronics Technology Using an Oscilloscope in Electronics Troubleshooting Testing overshoot and ringing in square waves shock excitation of RLC circuitry and transient waveforms in pseudo inductive circuits By Robert G Middleton Electronics we ve discussed using an oscilloscope in various troubleshooting applications See How to Read Oscilloscope Wave forms July and August 1988 and Waveshaping Circuit Action January 1989 This article is actually a continuation of those
139. h ends of all wires and sparingly tin with solder Plug one end of two of these wires into the holes labeled S3 from the solder side of the board and solder into place Similarly plug one end of the re maining wire into the hole labeled 51 from the solder side of the board and solder this into place Tightly twist together the fine wires at the ends of the 9 volt battery snap connector leads and sparingly tin with solder Plug the red insu lated lead of the battery connector in to the hole labeled Bi again from the solder side of the board and sol der it into place Temporarily set aside the circuit board assembly Now prepare the enclosure that will house the circuitry You can use any type of small enclosure you may have around or can locate in your lo cal electronics parts store An all plastic enclosure like the one shown in the lead photo is ideal However if you wish you can use a plastic en closure that has an aluminum cover plate as well Machine the enclosure to permit mounting of the circuit board assem bly to the cover plate switches 57 and S3 on the top wall and battery holder to the floor Note also that you must cut a rectangular slot in the cover plate through which the toggles on the DIP switch will be accessible The 1 inch diameter hole for the piezoelectric buzzer can begin as a inch diameter hole that can be en larged with a tapered reamer The dimensioned drawing shown in Fig 4 gives mac
140. hat has been selected by the control circuit 9 Head Assemblies These com prise the most delicate and sensitive part of the system since they are the actual elements used to record onto and play back from the ICM and OGM tape s The play heads sense the magnetic information stored on Volume Telephone Speaker circuit 1 AUDIO BUS Telephone coupling and 1 ad switching network Shae amplifier Microphone 10 A e Microphone C Fi amplifier AUG detector 5 counter OGM GE CREE 2 play Main microprocessor and control circuit E 4 OGM amplifiers ICM 1 MIN S 2 MIN Message ENABLES duration ICM VOX V timer record 7 8 Panel controls PLAY REW FF MEMO Security code Switches Motor speed Drive 3 and direction motor controls Fig 1 Block diagram of a simple telephone answering machine Say You Saw It In Modern Electronics March 1990 MODERN ELECTRONICS 19 TELEPHONE CIRCUIT Ring signal AN 90V RMS 20Hz Central office R Fig 2 Ring signal from Central Office alerts answering machine to pick up line after preset number of rings thetape and amplify those signals for distribution by the switching net work Information to be stored on tape is conditioned by the record am plifiers and output through the re cording heads to the tape s 10 Microphone Amplifier Thi
141. hat you do not touch or otherwise come in contact with the primary circuit of the power trans former Potentially lethal 117 volts will be present at the terminal strip lugs and the lugs of the POWER switch and fuse holder Turn on power to the project by setting the POWER switch to its position assuming you are using this switch If you are not using the switch dc power is automatically de livered to the various points in the circuit when you plug in the line cord With power applied touch the probe of the meter to pin 20 of the 1 socket and note the reading obtained It should be approximate ly 5 volts If you obtain this read ing touching the hot probe to pin 1 of the JC2 socket should also yield a 5 volt reading Touching the hot probe to pin 14 of the remain ing 14 pin and pin 16 of the remain ing 16 pin IC sockets should yield the same 5 volt reading If you fail to obtain the proper reading at any of the indicated IC socket pins immediately power down the circuit and pull the line cord from the ac outlet Rectify any 44 MODERN ELECTRONICS March 1990 WWW americanracdiohistorv com OUTPUTS PIN CLOCK OUTPUT NO DIVISION IN Hr CD4060 A A VIEW Fig 5 A CD4060 divider chip can be used to slow down project s clock os cillator for egsy observance of signal activity via logic probe or discrete LEDs wiring error s o
142. he Control Circuit disconnects the Tele phone Coupling Circuit from the line it resets the OGM and message duration timer for the next cycle Machines that have message displays increment or blink at this time to sig nal that an incoming message has been recorded e Playback Typically PLAY RE WIND and FAST FORWARD buttons are provided on the front panel of an answering machine to permit the ICM tape to be manipulated as in any other cassette recorder Fig 6 The PLAY button causes the control cir cuit to start the tape motor engage the ICM play mechanism and switch the amplified audio signal from the ICM play head to the machine s speaker output Sound level from the speaker is adjusted as desired with a VOLUME control in the Speaker Am plifier circuit In playback mode the Telephone Coupling Circuit makes no connection to the telephone line If remote control is used for play back however a connection is made to the phone line Features A wide variety of features appear in today s answering machines These vary according to the make and mod el of a given answering machine Among those that can be found are listed here though not all machines have all of them e Memo This feature permits the answering machine to be used as a traditional audio cassette recorder Fig 7 Pressing the MEMO button causes the ICM tape to start and re cord just lik a regular incoming mes sage However instead of reco
143. he Power Supply fea tures a built in three decade LED numeric metering system that can be used to monitor output voltage or current The project uses readily available components and is relative ly low in cost to build compared to equivalent commercial supplies About the Circuit Shown in Fig 1 is the complete sche matic diagram of the circuitry used in the Dual Polarity Power Supply The positive and negative voltage outputs that appear at binding poses and BP3 both referenced to common or ground binding post BP2 are adjustable The circuit is designed to give an adjustment range on both supply outputs of from 1 2 volts to a high that depends on the choice of power transformer 77 If you use a 48 volt transformer the maximum output voltage will be about 24 volts alternatively use of a 70 volt transformer maximum output will be about 35 volts By setting switch 82 to its alternate positions you can monitor either the positive or negative output voltage Switch SJ allows you to monitor pos itive or negative current depending on the setting of switch S7 Operation of the circuit begins with closing POWER switch 81 This delivers 117 volt ac line power to the primary of power transformer 77 The output voltage that appears across the secondary of is applied to the bridge rectifier composed of diodes DI through D4 these individ ual diodes can be replaced by an inte grated bridge rectifier module
144. he answering machine resets the outgoing message tape rewinds and plays the in coming message tape and transmits any recorded messages back to the calling party number he desires and to change that code from its remote controller stead of using a separate beeper de code at will Whatever the case the Should this occur you simply tap the vice Consequently beeperless oper remote controller and answering ma handset several times gently on a firm ation is preferred by most answering chine codes must be the same for the surface to loosen the carbon granules machine manufacturers system to operate properly and try the remote again Beeperless access can vary slightly Older telephone instruments em Beeperless Remote Control A from machine to machine Simple ploy carbon microphone transmit hand held beeper is an inconvenience beeperless machines are able to only ting elements in their handsets With if it breaks is lost loses battery play back recorded messages while the passage of time the carbon gran power is not at hand Many cur more complex machines will accept ules inside such a microphone can rent answering machines employ a subsequent codes to control such pack and shift resultingin poor aud beeperless system that permits the Other functions as change OGM io quality When this occurs the dis user to access messages and other ma turn on off the machine save re tortion introduced by the micro chine functions from
145. hining details for the cover panel if you use the size en closure specified in the Parts List Not shown are the mounting holes for the circuit board assembly These must be located according to where you drilled them in the circuit board assembly After machining the enclosure use a dry transfer lettering kit or tape la beler to label the switch functions and if you wish the name of the pro ject If you use dry transfer letters March 1990 MODERN ELECTRONICS 51 ahi Fig 2 Actual size etching and drill ing guide for printed circuit board for project 1234 R4 the R2 3 ca H Fig 3 Wiring guide for pc board protect them from scratching with two or more light coats of clear spray acrylic Allow each coat to dry before spraying on the next Mount 87 and 53 in their respec tive holes in the end panel and the battery clip to the floor of the enclo sure Then mount the circuit board assembly to the panel with suitable length spacers and 4 40 machine hardware Apply a thin bead of black silicone adhesive around the perime ter of the DIP switch assembly and piezoelectric buzzer to give the proj ect a more finished appearance Locate the wires coming from the holes labeled 53 and crimp and solder these to the lugs of the momentary action pushbutton switch Then crimp and solder the free end of the remaining wire to onelug ofthe slide toggle or push push
146. his sec tion decodes the binary data to hexa decimal format and routes it to the appropriate decade in the display string DISP1 through DISP4 Fi nally the proper segments of the ap propriate display decade must be turned on which is accomplished with another Electronic Switch un der control of the Electronic Switch Control amp System Clock block Normally the same segment turn on information is sent to all displays simultaneously Using a multiplex ing technique only one decade in the 38 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com RDNS EE mm i E Malesia ques 4 j Of 0000 cons ae Jes i T A i 1 J i Lj ogee et ect et te ne a ER C i se 4 7 5 i i Li b w Xx 4 oe ee I Vg y e voe ws 0 42 MNA 4 1 08 00 00 p i 5 PUPA spe ee sess bh igas _ display is swit hed ona any given in stant The multiplex switching is ac complished at a rapid enough rate that the eye perceives all display de cades to be on simultaneously each with its appropriate segments lit to display the correct data The 74C917 six digit hex display controller driver chip is
147. housands of exciting jobs in Communications Radio TV Micro wave Computers Radar Avionics and more You don t need a college degree to qualify but you do need an FCC License are guaranteed over temperature and 100 percent tested for no missing codes and total unadjusted error of 1 2 LSBor 1 No Need to Quit Your Job or Go To School This proven course is easy fast and low cost GUARANTEED PASS You get your FCC License or money refunded Send for high speed processor systems The ADC 912 0 to 70 C is available at 19 95 for 100 piece quantities ADC08031 Family National Semiconductor Corp Santa Clara CA recently introduced a family LSB Total unadjusted error includes offset linearity full scale multiplexer and track and hold errors Power con sumption is only 20 mW at 5V and maximum conversion and digital inter face times are both 8 microseconds The FREE facts now oe um Gum mm COUPON TODAY COMMAND PRODUCTIONS FCC LICENSE TRAINING Dept 220 P O Box 2824 San Francisco CA 94126 Please rush FREE details immediately NAME ADDRESS Say You Saw It In Modern Electronics March 1990 MODERN ELECTRONICS 67 WWW americanradiohistorv com WPC CAPERS The Winter 1959 COMDEX Report By Ted Needleman While you re reading this in March it s the beginning of D
148. iarala aat a e 222 ee 7 2 Ss ECCE imc co occ E High Fig 1 With every rotation of the Earth relative to the moon an ob server in the lighthouse would see two high and two low tides Clock project incorporates both in a single electronics package As can be seen in the lead photo the Tide Clock actually consists of two units a mo tor driven clock mechanism with its special dial face and a separate elec tronics package that powers the mo tor Though the project offers both powering opuons the 12 volt dc elec tronic drive approach is likely to be of more widespread interest because it has uses beyond that of a simple Tide Clock application The unique characteristics of syn chronous motors make this project possible and practical Synchronous motors are employed in clocks and other electromechanical timing de vices because their speed of opera tion depends on the ac line frequency used to drive them and on their rea sonable immunity to wear uneven loading and wide variations in pow ering voltage Although designed to be driven by a 117 volt ac sine wave signal synchronous motors can op erate satisfactorily with the square wave drive the power supply in our Tide Clock delivers The dependence of synchronous motors on line frequency makes them both reliable in normal applications easy to control in special applica tions One such special application is the Tide Cloc
149. ice and even at home It can be set to sound an audible alert at the end of a preprogrammed period lasting 5 10 15 or 30 minutes About the Circuit As shown in Fig 1 thanks to the ubi quitous 555 integrated circuit timer used for C only a few readily avail able components are needed to build this Snooze Alarm Small DIP switch assembly 82 permits you to select the duration of your snooze period When the snooze period has timed out piezoelectric buzzer PB sounds an audible tone to wake you Pressing and releasing START switch 53 starts the timing cycle The timing period depends upon the RC time constant generated by the values of any one of resistors RZ through R4 depending on which 15 selected by S2 and capacitor With the values specified for R through R4 snooze periods of approximately 5 10 15 and 30 minutes respectively are available with the 470 micro farad value specified for C7 Once the countdown period has begun the Snooze Alarm remains si lent for the selected period of time Upon completion of the countdown OUTPUT pin 3 of C7 powers PB to sound the alarm When you awaken at this point you shut off the audible alert simply by turning off power to 50 MODERN ELECTRONICS March 1990 WWW americanracdiohistorv com j the project by opening switch 57 The timing circuit is powered by common 9 volt transistor battery B The timing circuitry draws only 8 25 milliamperes of current
150. ice are they aren t the preferred device for everyone One interesting development that I came back from COMDEX with is called WIZ a refinement and extension of the mouse Developed by CalComp best known for plotters WIZ is a combina tion mouse and digitizer pad The WIZ looks pretty similar to other mice except for the pad it is attached to and the clear plastic reticle at the top of the mouse This reticle contains cross hairs in the center of a sensing coil and is what allows the device to be used as a graphics tablet The pad the mouse is attached to con tains additional circuitry and is about the same size as a standard mouse pad Completing the WIZ package are six mouse buttons each of the three buttons is a rocker switch different codes are generated if you push the top or bottom and a series of removable templates that fit on the sensing pad The WIZ can be used in several ways Once its drivers for DOS and or Win dows are installed it will function as a WIZ by CalComp combines ease of use features of a mouse and power of an intelligent graphics pad standard mouse Pressing button 5 the bottom position of the center button brings up the WIZ Manager utility Among other functions such as redefin ing the button functions this utility al lows you to set the mode that WIZ works in This can be to emulate a standard mouse or you can set the WIZ so that the pad boundaries correspond to the boun daries of
151. ieces P4008 37 500 64 P4107 390 500 68 5 81520 X050 He w 1 amp ns que 33 B 283203 23 UR a 5 A RS5X 5eachof values 100KQ to 1 00 0 29 95 P4009 26 800 64 108 2700500 a 5 0688 X082 HC 18 162 i360 7415169 123 74C010N 688 407 BCN 28 fm 254410 36 B 190 4 4010 68 500 2 5 1850 X053 HC 18 1 62 13 50 57 740911 10 45 so72BcN 50 2089 Ji puasa 30 ANASONIC SU SERIES DET eos 79 99 1380 74C812N 10 45 4073BCN 5 5 000 XO HC 1 1 1 ALS TOON ai 24 914 95 40758CN 28 285087 28 2428054 3640 30 Miniature Aluminum Electrolytic Capacitors 4142 1500 25 38 P4112 1000 500 8 Eig X054 HC 18 162 1350 2N5088 28 282906 89 PN3641 30 PA143 2200 25 99 P4111 1500 500 94 74151918 81 74 915 1 63 888 28 285089 28 2 2906 B3 PN3543 23 Axial Lead Radial Lead P4144 3300 25 88 P4116 100 1K 128 7 3728 X074 HC 18 1 62 13 50 74151939 91 74C917N 1045 40828 28 M 246712 29 2N2907 PN3644 32 WV Cap Digi Key Price Digi Key Price P4145 4700 25 1 09 P4117 120 0 128 E ae bs ez i 7445195 8 78 ARDOR 1 80 4086808 100 M 2N5224 24 2629078 0 PN3645 32 Part 1 Part No 2 cesis 128 26 x075 2 1250 241522144 83 7403 4 285226 23 283013 T 121 3 6 3 47 P6301 25 4147 1000025 1 13 119 180 3K 128 M 2 142 14152404 740323N
152. ight into new technologies and ow you can work with it 7 Trouble shooting techniques from the KS zzril 6s and how it works then the applica tions the maintenance and repair procedures C 8 Well organized easy to access information The FREE sturdy 3 ring Binder with Index Tabs organizes material so you find what you need quickly 9 Publisher s Moneyback Guarantee There s absolutely no risk in taking a look at The Modern Electronics Manual You pay nothing unless you are Pone satisfied it s for you If ou have paid already you will receive a full 100 of your money back No Risk Trial Certificate Just return the coupon below and we ll send you the Manual to look over in the comfort of your home or office Take the time it deserves to examine it carefully and then decide Send for your no risk look today ee ee Introduction to Satellite TV I To order your Manual right away call iques AWMWW americs tnradiohistorvy com Acct 1 800 222 WEKA The Modern Electronics Manual MESS 97 Indian Field Road Greenwich CT 06830 YES send me The Modern Electronics Manual for only 69 95 plus 4 50 for shipping and handling Enclosed is my check or credit card number and signature I understand if I am not completely delighted I can return the Manual at any time and receive a complete 100 refund O Bill
153. illoscope Hz to 40 MHz spectrum anaiyzer This high performance instrument provides up to 100 dB of dynamic range and a res olution of 3 Hz The CRT display gives a comprehensive readout of the instru ment s settings These and many other features of the Model 3585 can be had for a whopping 24 200 An instrument like the H P Model 3585 is totally beyond the financial reach of most electronics experimenters of course Fortunately an inexpensive al ternative is now available An Economical Analyzer Irecently had the opportunity to evaluate the Spectrum Probe a miniature probe like device that transforms almost any oscilloscope into a 1 to 100 MHz spec trum analyzer Shown in Fig 1 the Spec trum Probe is manufactured by Smith Design 1324 Harris Rd Dresher PA 19025 and sells for only 199 plus a nominal shipping charge The company accepts charge card orders at 215 643 6340 While the 199 price of the Spec trum Probe might seem rather steep for 60 MODERN ELECTRONICS March 1990 WWW americanracdiohistorv com such a small instrument particularly since it can be used only in conjunction with an oscilloscope this instrument is considerably less expensive than a con ventional spectrum analyzer Before proceeding I must point out that the Spectrum Probe shouldn t be considered as a replacement for a con ventional spectrum analyzer It doesn t provide the calibrated high resolution display of such prof
154. ing into place sockets for the DIP ICs Note that sockets for these chips are optional but highly recommended to ease re placement should any or all ICs fail during the life of the project Do not plug the ICs into their respective sockets until after preliminary volt age checks have confirmed that you have properly wired the project Continue wiring the circuit board assembly by installing and soldering into place first the fixed resistors and then the diodes and capacitors Make certain the diodes and electrolytic ca pacitors are properly oriented before soldering any of their leads into 34 MODERN ELECTRONICS March 1990 WWW americanracdiohistorv com place Next install and solder into place multi turn potentiometer R8 regulator and the JUMPER wire Use a cut off resistor or capacitor lead or a solid bare hookup wire for the jumper strip inch of insulation from both ends of eight 6 inch long hook up wires If you are using stranded hookup wire tightly twist together the fine wires at both ends of all wires and sparingly tin with solder Plug one end of these wires into the holes labeled Q1 BASE Q2 BASE ER SUPPLY and two wires LED CATHODE and LEDI ANODE two wires and TO 11 two wires Solder all wires into place Carefully examine all soldered connections Solder any connection you missed and reflow the solder on any suspicious connections you en counter A
155. io video disc player with multi disc carousel Sharp s Model MV D100 can handle 3 and 5 inch CDs 5 inch CD Videos and 8 and 12 inch videodiscs Its rotating carousel can accommodate any combination of 3 and 5 inch CDs including CD V for sequential play The player features a three beam laser pickup 8 x oversampling dual D A converters an optical output connection and an S Video output enables easy connection to a video monitor for picture quality with up to 420 lines of resolution Video spe cial effects include pause and still frame Full wireless remote control facilities are provided via a 53 key controller Among the player s other features isa time counter and mode indicator variable audio outputs for analog or digital sound tracks and a vhf out put with channel selector The player is fully programmable for special tape editing functions 1 499 95 CIRCLE 55 ON FREE INFORMATION CARD Frequency Source The key feature of Teledata Systems New Milford CT Wavebox 100 Synthesized Frequency Source is its 100 ppm 0 001 accuracy and sta CRUTCHFIELD Youll find the most helpful shopping infor mation in the 116 page Crutchfield catalog FREE Stereo Catalog Refer to the Crutchfield catalog before buying your next car stereo home stereo or video product 116 pages of helpful articles consumer tips charts and installation guides Color photos complete descriptions and tech
156. ip lead is attached to the input of the Spectrum Probe Notice the presence of distinct signals and areas of what ap pear to be noise The spikes that occupy the first one and a half divisions immedi ately to the right of the zero marker rep resent broadcast signals from several AM radio stations in my area The spikes that occupy the next few divisions are signals from more powerful shortwave radio stations These signals become more powerful and numerous at night Two of the three spikes shown at the right end of the screen are signals from two television stations in San Antonio TX The first is TV Channel 4 the third TV Channel 5 The small spikes just dis cernible near the 100 MHz point at the extreme right end of the screen are signals from FM radio stations The amplitudes of these signals is increased when a longer antenna is connected to the device When comparing relative amplitudes of the r f signals displayed on the oscillo scope screen keep in mind that the verti cal scale is logarithmic at 10 dB per divi sion Thus a signal with an amplitude of 100 millivolts is stronger than one with an amplitude of 50 millivolts You can use the oscilloscope controls to expand a particular portion of the trace for more detailed examination For example it s possibleto examine only the cluster of signals from nearby AM broadcast stations to determine which A Fig 2 Spectrum Probe oscilloscope display A without presenc
157. is a simple procedure Simply open the clock s case and re move all hands from the shafts of the drive motor If you wish you can save the hours hand for use as the pointer for the Tide Clock s display The minutes hand and seconds hand If there is one can be discarded Then dismount the synchronous mo tor from the clock case Building the clock hand and face depends on what materials are avail able You can go elaborate as was done for the prototype shown in the lead photo or you can simply use the clock as is just replacing the existing dial face with a new one with appro priate markings to distinguish it from ordinary standard clocks If you decide to go the elaborate route the dial face can be any sheet material plywood Masonite hard Say You Saw It In Modern Electronics Ile i wv aue nat pw A a A y an t W Aa 5 QUE ion 5 Fig 6 Machining details for rear panel of enclosure board plastic sheet or metal sheet you have handy and is thin enough to permit mounting the clock motor in its center with adequate clearance for the hours hand ring on the motor s shaft to mount the hand A inch or less thickness is about right for most clock motors Mark the dial face to easily distin guish it from normal solar clocks In stead of hours positions divide the display into two sections which you can label HIGH and LOW When the
158. iscount and service Charges are Simple to apply Most items Sold hy Key muy be comiined for volume discount hems that are not discountable ara Wentifient by the VOLUME DISCOU NT ND following the part number After writing your arder total all o rhe discountable items anc apply the appropriate discount To this subtotal add Ihe non discountable Then add the serwie T charge We pay all shipping and Insurance to addresses in the U S Canada and Mexico when check or money order accontganies order Digi Key only ships orders within the continental U S Alaska 100 00 249 99 Less 10 Hawai Canada and Mexico a a EM PT NA 750 00 3499 99 Less 15 WHEN DROERING BY PHONE CALL 1 800 344 4539 call 218 681 6674 BY MAIL SEND YOUR ORDER TO 0161 677 Thief River Fails 550 00 2 60 50000 499999 Less 20 You may pay by check money order Master Charge VISA or C DIGI NEY GUARANTEE Any parts ot products purchased trom Digs Kev thal prove to be detective will be replaced pr 1000 amp SEEN Less 2 ed it returned within 90 days From receipt with ol your mvoine PRICES SUBJECT RO CHANGE WITHOUT NOTICE CIRCLE 8 ON FREE INFORMATION CARD WWwW americanradiohistorv com GREEN TIE MAE ANTIQUE RADIO CLASSIFIED Are You Tired of Paying TS Outrageous Fees Free Sample foe 4 JN Antique Radio s Largest Circulation Monthly
159. its and memory storage a AME EU a DRESS ia ee e cC a March 1990 MODERN ELECTRONICS 75 Say You Saw It In Modern Electronics Digital recording quality can vary from one manufacturer to another depending on how much memory is provided for storage A small amount of memory 16 kilobytes for example will not hold enough digital data to reproduce good quality speech Larger memory like 32 kilo bytes or more will hold more data to reproduce a more faithful copy of the user s voice It is usually a good idea to test several machines in the store before purchasing one to make sure that reproduction quality of the digi tized voice is acceptable Instead of using a digitizer to re cord data in an EEPROM pre digi tized outgoing message data can be stored on a factory programmed PROM and installed in an answering Order Back Issues of FREE New Catalog of Hard To Find Precision Tools i im i mu 1 ee KI b LN I NW xxt i mm 3 f l ui uf 3 el UNS Ae Jensen s new catalog is jam packed with more than 2 000 quality items Your single source for hard to find precision tools used by electronic technicians scientists engineers schools instrument mechanics laboratories and government agen cies This popular catalog also con tains Jensen s world fam
160. ium batteries connected in series to make a 4 8 volt pack Battenes are in a 2 X 2 configuraton with a 2 pin connector attached The four batteries can be separated into single AA size solder tab nickel cadmium batteries or resoidered into other configurations SPECIAL SALE PRICE NOW 3 00 per pack 10 packs for 25 00 CAT NCB 41AAU LED S L E D FLASHER KIT KIT STEPPER MOTOR Airpax AB2743 M4 Brand new 12 volt dc stepper motor 35 ohm 7 5 degrees per step 2 25 diameter 0 93 long excluding shaft 0 22 dia shaft is 0 75 long 2 hole mounting flange 2 675 mounting centers 6 wire leads SMT 5 s ERR RA 10 00 each 6 50 each FLASHING LED with built in flashing to shut off automatically 2 92 X 1 97 X 2 54 behind face plate 1 47 half round shaft LOOK WHAT 1 00 GREEN the other Two leads CAT LED 6 2 for 1 70 Two piece holder B Ah CAT HLED 10 for 65 22 44 PIN CONNECTOR 10 SOLI STATE RELAY UL ae 156 pin spacing 0 200 between double rows gold contacts P C mounting SPECIAL Same as AMP 2 530655 6 CAT EBC 1G 1 00 each 10 for 8 00 Solder loop terminals PPC 200 3 25 each 10 for 30 00 100 for 27
161. k project presented here A synchronous motor can be thought of as a stepper motor whose output shaft advances a fraction of a revolution for every cycle of the ac drive signal To complete a single revolution in 12 hours and 25 min utes instead of the 12 hours exactly it would normally require a synchron ous motor must be driven at a slightly slower frequency than normal The new frequency must complete the same number of cycles in 12 hours and 25 minutes as the standard 60 Hz frequency completes in just 12 hours A frequency of 60 Hz completes 2 692 000 cycles in 12 hours The fre quency that completes the same num ber of cycles in 12 hours and 25 min utes is 57 9865772 Hz similar cal culation for telescope drive motors reveals that the correct frequency to accurately accomplish sidereal track ing with a solar telescope drive is 60 1643 Hz The power supply in this project offers morethan this range of adjustment to meet a variety of appli cation needs About the Circuit The complete schematic diagram of the project s circuitry including its ac operated power supply but not in cluding the drive motor is shown in Fig 2 Refer to this for the following explanation of circuit operation There are many ways to design an oscillator that will generate the re 32 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com quired frequency for our Tide Clock However the simplest reasonably ac curate approach
162. l Model odel zs MOX 9705 me Y IOS DUAL TRACE OSCILLOSCOPES AW SPERRY 20 MHz HITACHI 35 MHz ul OSCILLOSCOPE OSCILLOSCOPE 1 Built in component checker 19 calibrated sweeps 6 con nl Fordham 260 Motor Parkway Hauppauge New York 11788 74 3 filter e High sensitivity XY mode e Front panel trace rotator CRT with internal graticule scale illumination amp photo graphic bezel e Auto focus e XY Operation TV sinc separation e Includes 2 Z axis input Low power sumption TV Video sync e Includes 2 test probes probes 104 and 11 Model 52105 Model V 355 620C Reg 899 95 TRAINERS AND TOOLS ALL PURPOSE 92 PC TOOL CASE Complete kit for home workshop auto Includes 52 socket set with extenders 2 tool pallets with roomy rear storage compartments Attractive rugged carry case SCOPE DIGITAL TRAINER Learn logic circuits and equipment design Connects to oscilloscopes signal generators and more e Logic probe included Solderless breadboard and crib sheets help you build almost any circu t Runs off 4 AA batteries MOE IRS AC adapter included Reg 516995 o 1795 ASK FOR YOUR FREE CATALOG FREE 000 040 9918 In NY State 800 832 1446 221 Money orders checks accepted le E COD s require 25 deposit CIRCLE NO 130 ON FREE INFORMATION CARD i a Model DT 01
163. lar needs ME Say You Saw It In Modern Electronics Dual Polarity Power Supply from page 28 try hole for the line cord with a rub ber grommet Mount the circuit board assem blies in their respective locations us ing inch spacers and suitable ma chine hardware Then mount the transformer s fuse holders switches controls and binding posts in their respective locations Place control knobs on the shafts of the POSITIVE and NEGATIVE adjust controls Referring back to Fig 1 wire to gether all components and assem blies Make certain that you observe proper polarities for the LEDs and that you insulate all connections When you are done carefully go over the entire project to make sure all components except C4 and JC5 are in their proper locations that all connections are soldered and that all wire runs are correct The only real difficulty you may encounter in wiring together the cir cuit is wiring to switches SJ and S2 The best and surest way to wire to these four pole double switches is with the aid of an ohmmeter or audi ble continuity tester Use the meter or tester to determine the switching action as you go along With all the circuitry wired to gether there remains only to apply legends to the front panel of the en closure near the controls as shown in the lead photo Use a dry transfer lettering kit to apply these legends Remove the knobs from the POSI TIVE and NEGATIVE control shafts
164. le tubing to insulate the con nections to the LED and make cer tain that the LED is properly polar ized When this is done wire and SO into the circuit Mount the two power transistors on the rear panel If you are using a plastic utility box for the project s enclosure you must usea7 x 4 x 4 inch sheet of aluminum as a heat sink for the transistors You can bend this into a U shape if the height of the enclosure is less than 4 inches If you are using an all metal enclosure the enclosure itself will provide adequate heat sinking for the transistors Make sure the transistors are in sulated from the metal of the heat sink or metal enclosure Once they are mounted tie together their emit ters with alength of hookup wire and connect them to circuit ground at the lug of the fuse holder to which the negative lead of C5 is connected Crimp and solder the wire coming from hole A in the circuit board assembly and the secondary center tap lead of TZ to the solder lug ter minal strip to which the cathodes of D4 D5 and D6 are connected Next terminatethe two wires com ing from the Q1 Base and Q2 Base holes in the circuit board assembly to the bases of the transistors Mount transformer 77 and ac outlet SO to the rear wall of the enclosure Crimp and solder the remaining secondary Fig 5 Machining details for front panel of electronics package enclosure leads of the transformer to the collec tors of the tra
165. led to input pins 1 7 2 and 6 respectively of BCD seven segment decoder driver 4 In turn 8 provides the driv ing voltage for the selected segments in LED numeric displays DISPI DISP2 and DISP3 The numeric displays are enabled by output lines from 4 3 and 5 of C5 through driver transistors Q7 Q2 and Q3 The collectors of these tran sistors are connected to the common anode CA pins of DISPI DISP2 and DISP3 respectively When any given transistor is conducting it turns on enables the LED numeric display to which it is connected Trimmer control R70 across pins 8 and 9 of C5 is used to zero the dis play Trimmer control R9 between pin 13 of C5 and ground calibrates the voltage reading displayed The display must always be zeroed before connecting the output of the Power Supply to the display Re member that minimum supply po tential is approximately 1 2 volts Fig 1 Complete schematic diagram of the Dual Polarity Power Supply circuitry March 1990 MODERN ELECTRONICS 27 umerneanracdiannietorv ea I Once the display is zeroed by adjust ing the setting of R O calibration against a meter of known accuracy can be accomplished using R9 Three light emitting diodes are in cluded in the circuit Power on indi cation is provided by POWER LED2 Separate and voltage current indications are provided by LED3 and LEDI respectively Power resis tor R6 provides current limi
166. ledge and a COLLEGE DEGREE in your Technical Career through Add prestige and earning power to your technical career by earning your Associate or Bachelor degree through directed home study Grantham College of Engineering awards accredited degrees in electronics and computers An important part of being pre pared to move up is holding the right college degree and the abso lutely necessary part is knowing your field Grantham can help you both ways to learn more and to earn your degree in the process Grantham offers two degree pro grams one with major emphasis in electronics the other with major emphasis in computers Associate and bachelor degrees are awarded in each program and both pro grams are available completely by correspondence No commuting to class Study at your own pace while continuing on your present job Learn from easy to understand lessons with help from your Grantham instruc tors when you need it Write for our free catalog see address below or phone us at toll free 1 800 955 2527 for catalog requests only and ask for our degree catalog Accredited by the Accrediting Commission of the National Home Study Council GRANTHAM College of Engineering 10570 Humbolt Street Los Alamitos CA 90720 vf PICKS UP A WHISPER 50 FEET AWAY The model WAT 50 miniature FM tranmitter uses 4 stage circuit NOT to be confused with a simple wire less microphone Simply snap
167. lso check for solder bridges especially between the close ly spaced pads for the IC sockets If you locate any solder bridges re move them with desoldering braid or a vaccum type desoldering tool Now prepare the enclosure in which you will house the circuit board assembly and power supply circuitry Make sure the enclosure you select is large enough to also ac commodate POWER switch S7 power transformer 72 neon lamp indica tor assembly power outlet SOJ screw type terminal strip 7S7 fuse F7 inits holder and a solder type termin al strip on which to mount diodes D4 D5 and D6 and capacitor CS Machine the enclosure as needed to mount the circuit board assembly power transformer and diode capa citor arrangement on a terminal strip and the fuse holder on the floor pan el Through the front panel drill mounting holes for the LED banana jacks neon lamp assembly and Pow ER switch Also drill an access hole for R8 in a location at the lower right that provides easy access to the ad justment screw when the circuit board assembly is mounted in place Details for machining this panel Say You Saw It In Modern Electronics Fig 3 Actual size etching and drilling guide for project s printed circuit board along with typical lettering are shown in Fig 5 On the rear panel of the enclosure will be mounted the two position screw type terminal strip power transistors Q7 and Q2 transformer _ and recept
168. n 1 5 Volts IC6 74LS173 From Pin To 2 42 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com Ground IC6 Pins 8 9 15 thru Pins 2 8 9 15 Jl Pin 16 thru IC11 Pin 10 J1 Pin 4 J1 Pin 3 J1 Pin2 Jl Pin 1 5 Volts IC7 thru IC11 Pin 16 Jl Pin 15 IC7 thru IC11 74LS173 DISP1 DISF6 Pin a b g CK DISP2 Pin CK DISP3 Pin CK DISP4 Pin CK DISPS Pin CK DISP6 Pin CK Q1 Q6 Emitter C2 C1 R9 From To IC7 Pin 11 JI Pin 8 12 7 13 6 14 5 IC8 Pin 11 J2 Pin 4 12 3 13 2 14 1 IC9 Pin 11 J2 Pin 8 12 7 13 6 14 5 ICIO Pin 11 12 Pin 12 12 11 13 10 14 9 Pin 11 J2 Pinl6 12 15 13 14 14 13 Miscellaneous From To 2 IN C34 Bridge 4 COM C3 C4 Bridge Ground Bus OUT C4 5 Volt Bus DISP2 DISP6 Pin a DISP2 DISP6 Pin b R2 DISP2 DISP6 Pinc R3 DISP2 DISP6 Pind R4 DISP2 DISP6 Pin e R5 DISP2 DISP6 Pin f R6 DISP2 DISP6 Pin g R7 Q1 Collector Q2 Collector Q3 Collector Q4 Collector Q5 Collector Q6 Collector Ground Ground R8 Say You Saw It In Modern Electronic components Alternatively you can use perforated board with holes on 0 1 inch centers and suitable Wire Wrap or soldering hardware to mount and wire together the compo nents Whichever way you go though be sure to use sockets for all ICs and the LED numeric displays As shown in the lead photo the prototype of the project was assem bled on perforat
169. n analog input signal be converted to digital form for processing Naturally to do this you use an analog to digital converter In this month s column we ll examine A D con verters that use a technique called succes sive approximation Device Backgrounder One way to convert information from an alog to digital form is by successive ap proximation typical A D converter ADC of this type see Fig 1 is the ADC 912 from Precision Monolithics Inc Santa Ana CA It consists of a voltage reference a D A converter DAC a comparator a successive ap proximation register a clock and an out put latch The three state bus interface is for logic compatibility The functional diagram shows that the device uses a 12 bit DAC It also shows voltage reference at pin 2 that connects to the DAC the reference is 5V accord ing to the specifications for this particu lar device During system power up the ADC comes up in a random state Once the clock running at 1 MH2 is operat ing the first valid conversion begins with the application of a high to low transi tion on both CS chip select and RD read The next 13 negative clock edges complete the first conversion producing valid data at the digital outputs Now suppose we wanted to convert an analog potential of 6 3 V to digital form High to low transitions on both CS and RD initiate the conversion sequence the HBEN high byte enable input must be low too or
170. n only in more expensive ones When the machine answers an in coming call and finishes recording a message it automatically picks up the line again and dials out to any number or numbers preprogrammed into it After dialing the machine al lows the line to ring for a set amount of time If that line 15 answered the machine sends an identification tone that indicates at least one message has been recorded If there is no an swer from the ringing line the ma chine will re dial the number periodi cally until the line is answered Paging is a very handy feature to use with pocket beepers when such service is available Upon acknow ledgment of a page someone can call into the machine to access waiting messages e Remote Control This is used to unlock the messages contained in the Telephone AUDIO BUS coupling and Head amplifier Play ICM Main uP and d control circuit gt cassette recorder in the play mode March 1990 MODERN ELECTRONICS 23 machine and play them back over the phone line to the calling instrument To use this feature a caller dials the number of the instrument to which the machine is connected After the selected number of rings the ma chine picks up the line and begins to play the OGM At this point the re mote controller is placed against the mouthpiece of the telephone handset and a PLAYBACK button is pressed to generate a tone pulse train that should be unique to tha
171. ncandescent 3ulb 3 Etch away enwanted material in bath soluticn to create your printed circui eesy it is to am M __ 4 Attach coreponents and solder to board E 1 Filled with practical useful projects Over 400 pages of how to information that s easy to follow and makes PERDE faster easier and more enjoyable Now you can build your own electronic components in wide range of areas from telecommunications to stereos computers radio and TV j 2 Circuit layouts on acetate Save you time and effort Here s how to eliminate the most time consuming step of almost any project fabricating the printed circuit you need The Manual gives you the board layout in black on a clear acetate Just place the acetate over a photosensitive PC copper baseboard expose it to light develop it and you have your own punte circuit board specially crafted or each project 5 3 Save money by doing things yourself Build things for the home and office that make your life easier and more pleasant and give you more efficiency Learn when to call the repair man and Af loo today Here are just some of the subjects covered Electronic components and their characteristics Hand tools for electronic kit building Electronic component handling Electrical soldering techniques Saurces of electronic components Facsimile fundamentals Guide to using computer bulletin boards Short wave radio A DOS t
172. nical specifications on hundreds of the finest brand name products You get more value shopping at Crutchfield Toll free product advice ordering and customer service 24 hour shipping Absolute satisfaction guaranteed Full 30 day return privileges Discount prices on Sony Pioneer JVC Jensen Proton Advent Clarion Kenwood AR Infinity Bose and many more Call or send this coupon now for your FREE Catalog 800 336 5566 Be sure to mention Modern Electronics when calling Name Address Apt 4 City State Optional Are you in the market for PC products 11 fax copiers security products CRUICHFIELD 1 Crutchfield Park Dept ME Charlottesville VA 22906 ei March 1990 MODERN ELECTRONICS 15 NEW PRODUCTS bility over its 1 Hz to 100 kHz range Output frequency of this low cost in strument is dialed up directlv with thumbwheel switches on the front panel Resolution is rated at 1 Hz over the entire range of the instru ment The sine wave output is vari able up to 20 volts peak to peak with a 10 volt offset Harmonic and non harmonic distortion are both rated at better than 40 dB An auxiliary TTL CMOS level square wave Output is also provided 325 CIRCLE 62 ON FREE INFORMATION CARD Video Adapter Card Maxon Systems MVGA 16 video adapter card is said to be 100 IBM VGA compatible at both the BIOS and register levels It comes with drivers that
173. nonlinear through the peak frequency response region Overshoot and ringing are aggravated by rapid rolloff Fig 7 Plotof an RC amplifier that has rising high frequency response is equiva lent to a basic amplifier plus an RLC peaking network that has a moderately high Q a square wave test provides essential ly the same data in another form the reproduced square wave is easily fread out for evidence of nonlinear phase conditions From the viewpoint of test proced ures the optimum square wave fre quency depends upon the location of phase linearity Thus if there is signi ficant 100 Hz phase nonlinearity low frequency square waves will be reproduced with tilt but no visible distortion will occur at 1 kHz or 10 kHz On the other hand if there is significant phase nonlinearity at 3 MHz a high frequency square wave will be reproduced with overshoot and ringing but no visible distortion will appear at 100 Hz or 1 kHz repe tition rates Note that a direct coupled ampli fier in normal operating condition shows no phase distortion at any low square wave repetition rate How ever phase distortion will always be come apparent as the high frequency cutoff point is approached When troubleshooting electronic equipment with transient distortion it is desirable to make comparison waveform tests if possible with ref erence to a similar unit that is operat ing normally Comparative frequency response and
174. nrcode substitute 69 00 ECONOCODE WITH VARISYNC MLD 1200 3 Ch 3 outpu 7900 99 00 6200 MLD 1200 2 Ch 2 output ZENITH SSAVI CABLE INTERFERENCE FILTERS 3 only 99 00 62 00 125 00 14 00 EAGLE PD Dr SCRAN Ch on SCIENTIFIC AT LANTA Quantity Ma E ITE California Penal Code 8593 forbids us from shipping any cable descrambling unit to anyone residing in the state of Prices subject to change without notice PLEASE PRINT Name Address SUBTOTAL m Shipping Add 3 00 per unit COD amp Credit Cards Add 596 TOTAL California Li 38H City State _ Cashier s Check Acct O Money Order Phone Number 21 GOD O Visa Exp Date O Mastercard Signature _ FOR OUR RECORDS DECLARATION OF AUTHORIZED USE the undersigned do hereby declare under penalty of perjury that all products purchased now and in the future will only be used on cable TV systems with proper authorization from local officials or cable company officials in accordance with all applicable federal and state laws FEDERAL AND VARIOUS STATE LAWS PROVIDE FOR SUBSTANTIAL CRIMINAL AND CIVIL PENALTIES FOR UNAUTHORIZED USE Dated Signed 818 716 5914 Pacific Cable Company Inc 732
175. nside 4 are operat ing properly disconnect the project from the ac line and allow time for the charges to bleed off the capacitors Plug a 74LS138 into the 5 sock et Remove the LEDs you installed for C4 and temporarily connect them to pins 10 through 15 of C5 in the same manner as you did for C4 Leave the CD4060 connected as be fore Power up the project and ob serve the activity of the LEDs If you selected a low enough frequency through the CD4060 you should ob serve the LEDs counting in a repeat ing 0 to 5 sequence With operation of C5 confirmed pull the plug of the project from the ac outlet and allow the charges to bleed off the capacitors Then tem porarily tack solder suitable lengths of hookup wire to the 5 volt or ground buses in the project and ter minate the other ends at pins 1 of C6 through C to represent BCD data to these input pins Disconnect the LED resistors from C5 Carefully plug 74LS173s into the IC6 through 1 sockets Tempo rarily connect four of the LED resis tor combinations between pins 3 through 6 of and the 5 volt bus in the same manner as above Power up the project and observe the LEDs which should flash on and off in BCD sequence Once you ob tain LED activity power down the project and move the LED resistor combinations to between pins 3 through 6 of and the 5 volt bus and repeat the test Do this for IC8 through in turn to verify opera
176. nsistors Mount 77 and 1 in their respec tive locations on the rear panel of the enclosure Slide suitable lengths of plastic tubing over the leads of non polarized capacitor C4 and crimp but do not solder the capacitor s leads to the lugs of the chassis mounted ac outlet Crimp but do not solder the primary leads of the transformer to the lugs of the outlet Prepare two suitable lengths of hookup wire and crimp one end of each to the lugs of the ac outlet Solder both connections Slide a 1 length of small di ameter heat shrinkable tubing over the free ends of the two wires Crimp and solder these wires to the leads of neon lamp assembly on the front panel When the connections cool slide the tubing over them to com pletely insulate the connections and shrink the tubing into place Terminate the free end of the wire coming from hole B in the circuit board assembly at the junction of D4 and secondary lead of 72 Solder the connection Then crimp and solder the free ends of the wires coming from holes J1 and J2 to the lugs on the 36 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com jacks mounted on the front panel observe polarity Finally plug a 3 ampere fuse into the holder This completes assembly of the power supply portion of the project Set this assembly aside until later and proceed to fabricating the Tide Clock s dial motor assembly Modify an existing ac operated an alog clock
177. nt panel does sport a unique assortment of manual override switches that provide one touch access to functions that in clude manual or auto answer Self test di agnostics changing data rate switching between voice and data and a Sync switch that selects between asynchronous communications and a special Racal Va dic synchronous communications mode All the above functions can be used in dividually or in combination to establish a modem communication link without the need of a software communications package This makes the unit suitable for stand alone mainframe and terminal use The status of the switch settings and mo dem operation are displayed via 11 LEDs The Model 9632VP also has an MI MIC Mode Indicator Mode Indicator Common connection that allows you to add an external Bell 801 type device such as a dial back security system that pre vents unauthorized persons from gaining access to your system to the modem The Model 9632VP uses the AT com mand set which was invented by Hayes Se a ee eS H Say You Saw It In Modern Electronics March 1990 MODERN ELECTRONICS 57 WMWW americanraciohistorv com SCIENTIFIC amp ELECTRONIC GRA1 ANTI GRAVITY GENERATOR 10 00 w LC 40 WATT BURNING CUTTING LASER 20 00 lt 25 RUBS POWER PULSED DRILLING LASER 20 00 BTCS t MILLION VOLT TESLACOIL 20 00 92 MCP I HI VELOCITY COIL 15 00 e
178. nted circuit board you make yourself or on perforated board that has holes on 0 1 inch centers us ing appropriate Wire Wrap or solder ing hardware Whichever technique you choose though it is a good idea to use a socket for the timer chip If you wish to use a printed circuit board use the actual size etching and drilling guide shown in Fig 2 to fabricate one When the board 15 ready drill a hole in each of its four corners in locations where they will not interfere with any conductor runs and place the board on you work sur face oriented as shown in Fig 3 Note Usethelayout shown in Fig 3 asarough guideto component place Say You Saw It In Modern Electronics ment if you wire the circuitry on per forated board Install and solder into place the IC socket but do not plug the 555 in the socket until after you have conducted a voltage check upon completion of assembly of the project Then install and solder into place the piezoelectric buzzer observe polarity resistors and the DIP switch assembly Plug the leads of the capacitor into the holes in the board from the conduc tor trace side of the board anc solder them into place Be sure you properly orient the capacitor before soldering its leads to the copper pads on the bottom of the board Strip inch of insulation from both ends of three 4 inch long hook up wires If you are using stranded wire tightly twist together the fine conductors at bot
179. ntial An expo nential waveform represents the na tural physical law of growth and de cay The rate of decay is determined by the winding resistance of the in ductor and effective shunt resist ances such as eddy currents and ra diation resistance Transient Response of Tuned Transformers Let us now consider the ringing waveforms provided by a transform er with tuned primary and tuned sec ondary such as an AM i f transform er Frequency response curves for a 46 MODERN ELECTRONICS March 1990 WWW americanracdiohistorv com Fig 1 Test setup that minimizes circuit loading for displaying a ringing waveform typical transformer with three de grees of coupling are shownin Fig 3 Here M denotes the mutual induc tance that exists between the primary and secondary windings of the trans former and k denotes the coefficient of coupling Notethat the equivalent circuit shown in Fig 3 A shows the series parallel RLC primary circuit asits Thevenin equivalent series RLC network which simplifies analysis of transformer action The key to understanding tuned transformer ringing waveforms is recognition of the double humped frequency responses in Fig 3 as the equivalent of two RLC networks tuned to slightly different frequen cles Observe in Fig 4 that when a tuned transformer with double humped frequency response is shock excited by a square wave a more com plex ringing waveform is produced than by a single n
180. ntrols and Descramblers JERROLD OAK ZENITH EAGLE HAMLIN SCIENTIFIC ATLANTA Many more Fast courteous service Call today 512 250 8816 or write for your Free catalog CABLE TV BOXES Descramblers Converters Some Of The Best Prices In Town T J SERVICES 313 979 8356 Nu Tek Electronic 5114 Balcones Woods dr Suite 307 Dept 298R Austin Tx 78759 CIRCLE NO 143 ON FREE INFORMATION CARD 80 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com COMPUTERS ENGINEERING Software PC MSDOS Hobbyists Students Engineers Circuit De sign 59 FFT Analysis 69 Mathematics 49 Logic Simulation 49 Circuit Analysis 29 FREE Catalog 614 491 0832 BSOFT SOFTWARE 444 Colton Rd Columbus OH 43207 FREE Software for IBM or compatibles Info 1 00 Blue Chip Engineering P O Box 1100 Walnut CA 91789 PROJECT SUPPLIES PROJECT Supplies Tools Motors Casting Surplus Materials Catalog 1 Inventors Hardware Box 8460 M Anaheim CA 92812 MISCELLANEOUS STRESSED Out Relaxation technique easily learned with the aid of a simple electronic de vice NOT hypnosis Plans 9 95 Blue Chip Engineering P O Box 1100 Walnut CA 91789 DANCE Like A Pro Exciting report reveals how you can use a VCR to learn almost any dance step Send 15 00 payable to P A Perez P O Box 7610 Alhambra CA 91802 POPULAR ELECTRONICS FROM VOL 1 NO 1 OCT 1954 THRU NO 69 OTTO
181. o The star of COMDEX was a similar sized unit from Poquet The Poquet while still only slightly larger than a VHS cassette has a very usable keyboard a much larger screen than the Portfolio much more RAM anda several thousand dollar price tag Also in evidence were new note book sized laptops such as the Toshiba 1000SE the Panasonic 150 and the one possibly destined to be the most popular of them all the Compaq LTE Compaq s LTE notebook computer comes in two versions the PC compatible 8086 LTE and the 80286 286 LTE versions Key options include left to right external Fast Charg lt er ac Adapter numeric keypad 5 inch floppy disk drive or 40 MB hard disk Compaq 286 LTE The 286 1 is a notebook PC It s called that because it is almost the exact size of a thin three ring notebook With in its small 8 5 by 11 inch package is complete PC including a minimum of 640K of RAM and a 1 44 MB 3 5 inch floppy disk drive Available options al low the LTE an 8086 based system and 286 LTE to be internally expanded with up to 2 MB of additional RAM and a 20 or 40 MB hard disk drive The 286 version of the notebook can also accept a 12 MHz 80C287 math co processor And both the 8086 and 80286 versions have provisions to accept a sec ond serial port or internal 2 400 baud modem My review unit was the 286 LTE equipped with the 2 MB RAM up grade a 20 MB hard disk and the int
182. of the body After a few clicking sounds it ll beep and you can read the measure ment in feet or meters if you press a mode button Pressing a dimension but ton length width or height stores the in formation into memory Follow this with an ultrasonic measurement of another di mension for area store it and then press an Area button Total square feet will then be calculated and displayed For volume a third quick long distance measurement is made and pressing Vol ume provides that information too Turning the Home Contractor over to get at its other side reveals a conversion computer also with an LCD display This side has a series of soft switch buttons including four banger calcula tor buttons Simply enter the area or vol ume that you had measured previously and press a materials button paint rug etc onthesame face Doing this a built in software program automatically cal culates how much material you ll need to do the job in appropriate form That is if 6 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com you press Paint the readout will indicate how many gallons you ll need press Roll and the result will be in wallpaper rolls re quired press 4 x 8 and you ll read how many wal panels you ll require There are factors you can punch in to change the 4 x 8 to another dimension if wall panels you choose are not a standard size and subtractions to account for doorways window
183. omputer training includes all this NRI s unique Discovery Lab for circuit design and diagnosis NRI s hand held digital multimeter featuring talk you through instructions on audio cassette A digital logic probe that lets you visually examine computer NOW AT compatible prepared to take advantage ircui f today s circuits The new 0 AT compatible West puter 20 Coast 1010 ES computer Ww h rd dri with high speed 80286 1 CPU 101 intelligent i 2 adi eg a You learn at your keyboard 1 2 meg high density own convenience in floppy disk drive 1 meg RAM 23i s dal P NF your own home expandable to 4 meg 64K ROM E 4 NDS ressures no night school no need to quit your present job until you re ready to make your move And all throughout your training you ve got the full support of your personal NRI instructor and the NRI technical staff always ready to answer your questions and help you whenever you need it 20 megabyte hard disk drive MS DOS GW BASIC word proces sing spreadsheet and database software Reference manuals with programming guidelines and schematics d E acm FREE 100 Page Catalog Tells More Send today for NRI s big 100 page catalog that describes every aspect of NRI s innovative computer training as well as hands on training in other growing high tech career fields
184. on slots gt Dual FDD HDD controller 2 half height drive cavities exposed a 1 half height drive cavity enclosed 2 Serial ports 1 parallel port System configuration in CMOS with battery back up Included software MS DOS 3 3 amp GW BASIC 145W Universal power supply Socket for 80287 co processor on motherboard Zero wait state One Year Warranty rt Y Y NEW F FACTORY P Y PERFECT FACTORY Manufacturer s Suggested Retail Due to a special ar rangement we were able to obtain alarge 3 449 00 inventory of these DAMARK PRICE PRICE computers with color monitors As a result we can now offer them to you at HUGE SAVINGS Item 1825 132142 Insured Ship Hand 39 00 FOR FASTEST SERVICE CALL TOLL FREE 1 800 729 9000 p VISA MasterCard DAMARK INTERNATIONAL INC 6707 Shingle Creek Parkway Minneapolis MN 55430 Customer Service 612 566 4940 Please rush me Packard Bell Computer s 9 1499 each plus 39 00 s h each Item No B 1825 132142 MN res add 6 sales tax Address City 2 ChecwMO VISA D Master Discover Nors Exp Date o Signature DELIVERY TO 48 U S STATES ONLY CIRCLE NO 138 ON FREE INFORMATION CARD Say You Saw It In Modern Electronics March 1990 MODERN ELECTRONICS 71 WWNW americaanradiohistorv com Telephone Answering Machine page 24
185. or across Vpp to ground and Vss to ground In applications where the ADC data outputs and control signals are connected to a continuously active microprocessor bus itis possible to get LSB level errors in conversion results These errors are due to feed through from the microprocessor ELECTRONICS AND YOU PART 1 DC Price 32 95 Series Circuits parallel circuits combination of series parallel circuits OHMS law voltage current and resistance ELECTRONICS AND YOU PART 2 AC Price 32 95 AC theory coils transformers capacitors filter circuits and how they are used in actual circuits ELECTRONICS AND YOU PART 3 SEMICONDUCTORS Price 32 95 An introduction into the world of semiconductors Starts with semiconductor theory then proceeds into 15 different semiconductor devices Shows how an integrated circuit is designed and built ELECTRONICS AND YOU PART 4 POWER SUPPLIES Price 32 95 Starting with the transformer then to various types of rectifier circuits Filter circuits voltage protection Trouble shooting different parts of the power supply VCR MAINTENANCE AND REPAIR Price 32 95 Designed for the average VCR user Learn how to clean the tape path replace belts plus more must for home maintenance INTRODUCTION TO VCR REPAIR Price 59 95 Shows how the VCR processes the luminance chromance and audio signals in playback and record modes Servo systems for controlling the capstan motor and vi
186. ors and C3 provide by passing to ensure stable circuit opera tion Their values are not critical to proper operation of the project Integrated circuit JC3 contains six buffered inverter stages The square wave output from 7C2that couples to pins 5 7 9and 11 of C3 emerges in verted at pins 4 6 10 and 12 of the IC Note that the output at pin 4 of IC3 provides a means for monitoring Say You Saw It In Modern Electronics R2 10kKQ XR 2206CP FINE ADJUST FREQUENCY COUNTER of a 4049 12 VDC INPUT 4 A F TEST PROD are each 1 6 each 1 6 of a 4049 2 3055 SEC PRI PINOUTS 2N3055 Bs E E C Fig 2 Complete schematic diagram of Tide Clock electronic drive circuitry the frequency of the oscillator with an external frequency counter Inverters JC3A and C3B drive light emitting diode at the beat frequency mathematical dif ference of the oscillator and a 60 Hz pulse train obtained from the 117 volt ac line through D3 R6 and R7 The remaining inverters in C3 are used to obtain the alternating pulse trains needed to bias transistors Q7 and Q2 One of these pulse trains passes through three such stages to reach Q2 This puts the drives to the two transistors out of phase with each other so that when one is con ducting the other is held in cutoff and vice versa Integrated circuit C4 simply serv
187. ould again sound and continue to do so until you set S7 to off If the project operates as described for the shartest timing interval you might want to ascertain operation for the other intervals This will take a bit of time to accomplish because each successive switch in the DIP switch assembly increases the snooze timing period Also each DIP switch should be set to when another time is selected For example if switch 2 is selected switches 1 3 and 4 should all be off so that only a 10 minute countdown period is selected by switch 2 Bear in mind that times stated are only approximate If you want more accurate timing it may be necessary to add to or subtract from the resis Cantinued on page 82 a ee ee 52 MODERN ELECTRONICS March 1990 Www americanradiohistorv com Say You Saw It In Modern Electronics BOOKS Z Modern Television Service and Repair By Stan Prentiss Prentice Hall Hard cover 356 pages 33 Written by one of the most prolific expert authors of television servicing articles and books this volume is a font of useful infor mation It bridges the history of TV receivers starting with the 1950s and working up to the most up to date topics in the tech nology Starting with a catch all Then and Now chapter that contrasts the old with the new the book moves on to an analysis of modern TV receiving systems Following the two introductory chapters
188. ous line of more than 40 tool kits Call or write for your free copy today 7815 S 46th Street JENSEN Phoenix Az 85042 TOOLS INC 602 968 6251 CIRCLE NO 129 ON FREE INFORMATION CARD machine built for SSOGM Speech Synthesized Out Going Message This simplifies machine electronics by eliminating the need for the digi tizer recorder network Fig 8 and uses only a reconstruction network Fig 10 A simple less expensive prerecorded PROM holds the fixed message usually generic such as Hello no one is available at the moment Please leave your name number and message after the tone Someone will get back to you Thank you The digitized voice can be either male or female but the lower frequency components of the male voice can usually be digitized with less memory Date amp Time Stamp Another ap plication of digital speech synthesis is BU FRANKLIN BELLE PUBLISHERS The Antenna People Present MAGAZINES eantenneX A monthly magazine all about antennas Read in 40 countries eBOOKSe eRules of the Antenna Game By Ted Hart W5QJR eSmall High Efficiency Antennas By Ted Hart W5QJR eElectronics for the Radio Amateur By James Lee W6VAT 19 95 eSOFTWARE IBM e eTransmitting Loop Antenna eTransmission Line Antenna eAntenna Utilities Series 1 eNoise Analysis Program eCapacitor Design Program eOTIIERe eWiperless Capacitor Plans TO ORDER Send Check or MO plus
189. over date Send Advertising material with check or money order or credit card information Visa or MasterCard only with number and expiration date to MODERN ELECTRONICS Classified Department 76 N Broadway Hicksville NY 11801 MINIATURE Electronics like James Bond VIDEO Catalog 3 00 refundable F amp P Enterprises DESCRAMBLERS All brands Special Box 51272 Palo Alto Calif 94303 H Combo Jerrold 400 and SB3 165 Complete DETECTION Surveillance Debugging cable descrambler kit 39 Complete satellite Plans Kits Assembled Devices Latest High descrambler kit 45 00 Free catalog MJO Tech Catalog 5 DETECTION SYSTEMS INDUSTRY Box 531 Bronx NY 10461 0531 2515 E Thomas 16 864H Phoenix Ari VHS VCR Repair Solutions Sets I II III IV Zona 85016 V Each contains 150 symptoms and cures cross reference chart free assistance 11 95 each all five 49 95 Eagle Electronics Box A 52053 Locks Lane Granger IN 46530 T V NOTCH FILTERS SURVEILLANCE EQUIPMENT BROCHURE 1 00 D VIDEO BOX 63 6025 MARGATE FL 33063 1 305 752 9202 BUILD mini F M bugs supersensitive long range step by step plans 4 95 Poobah Elec tronics Box 3816 Farmington NM 87499 ELECTRONICS COMPUTER Manuals Software Hardware Services HIGH VOLTAGE DEVICES SECRET SUR VIVAL RADIO COLOR BOXES ELECTROMAGNETIC BRAINBLASTER RADIONICS DISK SERVICE MANUAL COMPUT
190. peed Erase Any time an ICM tape is rewound and positioned at its beginning any new messages will be recorded over messages previ ously recorded on it Some machines have an Erase function that cycles the 510 2 5 Volts ICM tape from end to end at high speed and erases the entire contents of thetape This very useful function protects personal or sensitive mes sages from unauthorized playback after they have been reviewed Multiple Line Capability Most machines are built to handle only one incoming telephone line However more sophisticated machines will handletwo incoming telephone lines which is ideal for businesses run in a home where one line is for private use the other for business use With such machines a personal message can be left for the private number and a professional message can be left for the business number e Power Failure Protection If pow er should fail an answering machine normally loses count of the number of recorded messages and its current ICM tape position When power is restored the machine will ignore any previous recordings and start from a fno message state To protect the message count tape position and any other memory related functions some machines use a power failure protection scheme Batteries are typically used to pro vide this power failure protection in answering machines The machine may still function properly without its battery but a power failure will
191. program fully dBase3 compatible 3 disks 2 disk 271 The Draw great ANS drawing animation disks 185 168 QModem 4 1 The standard in modem communications programs 2 disks 4 disk 1120 Total Ham a great multi function log ging operating ald for the radio amateur 5 disk 1149 GeoClock a real time grayline map of the Earth Like DX Edge order disk 1150 for EGA VGA 8 disk 1089 Mapper EGA worid map that shows grayline beam headings distance MUF LUF and morel ram that to zoom In on any location Includes built in hurricane tracker S mCGA allows you to run CGA programs on a monochrome monitor 8 disk 51 AutoMenu THE industry standard in easy to use menuing programs 10 disk 290 FlowDraw a top shareware flowchart ing schematic diagramming system with WYSIWYG 11 disk 211 As Easy As version 4 0 of THE Lotus 1 2 3 spreadsheet clone 12 disk 728 Personal C Compiler a great share ware C compiler With editor library make and debugger 13 disk 1099 T8440 759840 Rig Control contro your Kenwood rig with your computer 14 disk 735 GTE s DOS Tutor a top natch easy to use graphically oriented interactive tutor 15 disk 1081 Ham Radio 1 Packet reiated YAPP amp PackTalk terminal programs 18 disk 1110 KIEA s DX Contest Logger ver 4 25 lof the standard contest logger 17 disk 1145 PK232 Packet terminal program dedicated
192. programs Call or write for details today Call TOLL FREE 1 800 776 1900 Cleveland Institute of Electronics Inc 1776 East 17th St Cleveland Ohio 44114 AMO 167 C1 YES Please send me your independent study catalog For your convenience CIE will have a representative contact you there is no obligation Print Name eee Address Apt City State Zip ___ sS Age Area Code Phone No Check box for Bill bulletin on educational benefits Veteran D Active Duty Mail This Coupon Today RT WWe americanracdiobistorv com B I R D E MODERN ELECTRONICS THE MAGAZINE FOR ELECTRONICS amp COMPUTER ENTHUSIASTS Battery operated InfraRed Detector MARCH 1990 Parts Express introduces the first Battery operated InfraRed Detector pen This compact device will instantly confirm operation of infrared emitting prod ucts Indi cates presence of infrared in normal light Slim design easily reaches IR emitters on crowded VCR circuit boards This low cost and easy to use Instrument will soon become standard equipment for all techni cians in the consumer electronics repair industry CALL TOLL FREE 1 800 338 0531 Parts 340 E First St Dayton Ohio 45402 Phone 513 222 0173 FAX 513 222 4644 CIRCLE NO 133 ON FREE INFORMATION CA
193. put is at full scale 1111 1111 1111 Offset Error The deviation of the ana loginput voltage from zero when the digi tal output is at all zeros 0000 0000 0000 Integral Nonlinearity INL amount that the actual analog input volt age deviates from the ideal analog input voltage for any digital output code after March 1990 MODERN ELECTRONICS 65 Say You Saw It In Modern Electronics WWweamericanradiohistoryv com SOLID STATE DEVICES TO 10V 5k Fig 2 The ADC 912 has a 2 500 input resistor that connects to the same comparator input as the external 5 000 ohm resistor that couples the input signal into the device the gain and offset errors have been ad justed to zero This number is expressed in LSBs or fraction of LSB For example a maximum INL of LSB is equiva lent to 1 22 mV for a 12 bit ADC with an input range of Oto 10 V Differential Nonlinearity DNL This is the difference between the actual change required to cause a digital output to change 1 LSB and the ideal change For example for a 12 bit ADC with a 0 to 10 range an analog output change of 2 44 mV should cause the out put to change from 0000 0000 0000 to 0000 0000 0001 If it actually took 4 88 mV the DNL would be 1 LSB LEARN ELECTRONICS FROM VHS VIDEO TAPES PREPARE FOR THE FUTURE NOW Video Tapes Designed Especially For The Electronic Enthusiast
194. r cost 559 95 MTS TV STEREO DECODER Hear true stereo TV sound Receives bilingual programming Dolby Noise Reduction Sleek high tech technology SPECIAL 99 95 WIRELESS DOOR CHIME m INDOOR FM STEREO ANTENNA Superb antenna isolates the main FM signal No more FM station drift or fading with the Beamaster Features built in amplifiers adjustable gain control EACH 549 95 2 For 39 95 EACH 1 800 826 7623 4030 BEAU D RUE DRIVE EAGAN MN 55122 612 452 8420 Now have remote door chimes with no wiring Simply plugs into any electrical outlet Effective up to 50 feet apart PRICE 30 00 CIRCLE NO 125 ON FREE INFORMATION CARD March 1990 MODERN ELECTRONICS 59 T ELECTRONICS NOTEBOOK Experimenting With an r f Spectrum Analyzer By Forrest M Mims HHI Testing and alignment of a radio fre quency transmitter is considerably simplified if an r f spectrum analyzer is used This valuable instrument also per mits you to survey your environment for the presence of r f radiation and check equipment for unwanted r f emissions This time around I ll begin by describ ing a new kind of r f spectrum analyzer that costs considerably less than conven tional analyzers Then I ll detail how this instrument can be used to check for r f signals Finally l IIshow how a spectrum analyzer can be used to aid testing and aligning a miniature r f transmitter Spectrum Analyzer Basics
195. r reverse polarity di ode or and filter capacitor connec tions you might have made in the power supply section or errors in wiring you might have made in the rest of the circuit before proceeding to operational checks Once you are certain of your wir ing power dawn the project by pull ing the plug from the ac outlet Al low sufficient time for the charges to bleed off the filter capacitors in the power supply Then carefully plug the CD4049 into the 7C2 socket Make sure th t no IC pins overhang the sockets or fold under between de vices and sockets To accuratdly check clock genera tor 2 you should use an oscillo scope or frequency counter If you have access to neither you can use a CD4060 divider chip to slow down the output signal from C2 so that it can be verified with a logic probe Plug the CD4060 chip into a small solderless breadboarding socket Us ing suitably long flexible wire leads connect pins 8 and 12 to circuit ground and pin 16 to the 5 volt buses in the project Similarly con nect a lead from output pin 11 to pin 1 of the 4 socket in the project Power up the project If you have a scope or counter monitor the out put of the clock generator at pin 2 of IC2 You should obtain a frequency reading at this point of approximate ly 20 8 kHz If you are using the Say You Saw It In Modern Electronics CD4060 circuit refer to the table in Fig 5 for details of where to pick off the divi
196. r the LED numeric display switches controls LEDs and bind ing posts If you incorporate a fixed 5 volt hA in your project you must also take into account the space required fof it Machine the enclosure as needed That is drill mounting holes through the front pane for the POSITIVE and NEGATIVE adjust controls output binding posis POWER switch es and LEDs Also cut slots in the panel for the two pushbutton switches and window fon the LED numeric dis play Locate these slots accurately Then drill the mounting holes for the circuit board assemblies fuse holder s and transformers through the floor and or rear panel of the en closure Also drill an entry hole for the ac line dord When you are fin ished machining the enclosure de burr all drilled holes and cut slots to remove shagp edges cement red transparent plastic filter over the dis play window cutout and line the en ae on page 77 Say You Saw It In Modern Electronics Uf heebb and flow of tidewater being most influenced by the moon ordinarily do not oc cur at the same rate as the standard 24 hour solar clock Therefore a dif ferent kind of clock is needed to keep track of high and low tides a Tide Clock like the project presented here It can beahighly valued indicator for people living near a shoreline wheth er for swimming boating or fishing At the heart of our Tide Clock is a 117 ac power supply that drives synchrono
197. rator is tied to analog ground AGND the comparator output is driv en high This leaves the MSB high for the remainder of the conversion The process continues with the next bit raised high 1100 0000 0000 and then tested If the voltage at the comparator is positive the bit is kept high if not it is changed to a zero and the next bit is tested This con tinues until all bits are tested Once a conversion cycle is started it cannot be stopped or restarted without upsetting the remaining bit decisions Every conversion cycle must have 12 neg ative CLK IN edges At the end of con version the comparator input voltage is zero The SAR contains the 12 bit data word representing the analog input volt age The BUSY line returns to logic high signaling the end of conversion TheSAR transfers the new data to the 12 bit latch When the negative edge of RD is aligned with the positive edge of CLK IN the conversion takes 12 5 microseconds Key Parameters Let s now look at some of the key parameters of the ADC 912 e Conversion Time Thetime required to convert the analog input voltage to a digi tal output code e Resolution The number of digital out put lines 12 bit ADC has 12 digital output lines Twelve lines allow the ADC to have 4 096 steps or analog voltages that can cause the LSB to change from 0 to 1 or vice versa Gain Error The deviation of the actual analog input voltage from the ideal when the digital out
198. rcuit Alterna tively you can install an spdt switch in theline that goes from pin 7 of 4 one switch throw or stationary con tact and pin 16 of the switch pole er toggle and run a line from the 5 volt bus to the remaining switch throw With this arrange ment when you want to extinguish the display you simply set the switch toits 5V position If you want to be able to adjust the brightness of the display you can drive pin 1 of JC with a variable fre quency pulse generator Such a gen erator can easily be assembled around a commonly available 555 or other timer chip Schematic dia grams for building a variable fre quency pulse generator can be found in a wide variety of electronics maga zine articles and books The second ripple counter inside IC4 is also wired as a BCD decade counter Its pins 10 and 11 outputs go to the inputs of one gate inside IRIS CEDUPEGORECPUPUS IG UE ME GER c ce NEM LLLA Se UU UE cc c uw March 1990 MODERN ELECTRONICS 39 Say You Saw It In Modern Electronics Er WE iponEss 2 FER 9 sureen 2 od Eee 5 BIT NPUT BUS m 1 g e Fig 2 The 74C917 six digit hex display controller driver chip around which project is built contains circuitry that performs nearly all functions diagrammed ADDRESS DECODE INPUT DATA 5 s OUTPUT 5 BUFFERS in Fig 1 841 500 quad NAND gate C3 at pins 9 and 10
199. rding the caller s voice from the telephone line the voice of the person speaking is recorded through the machine s pickup Use of the memo function makes no connection to the phone line Pressing the MEMO button again exits 1 2 Caller hangs up idle Caller s line becomes 3 Central office senses caller s phone on hook Central office R Central office senses a CPC pulse before reverting to dial tone CPC pulse 5 Machine detects propriate CPC pulse and disconnects Answering machine selector switch Fig 5 The CPC switch usually offers a choice of pulse duration and positions to accommodate differences in Central Office equipment 22 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com Say You Saw It In Modern Electronics HOMER memo mode increments the ICM count and displays the presence of the memo on the tape just as it would a normal incoming message The memo function can be very useful when it is necessary to leave a mes sage to other people who share a machine and check messages e Message Display This indicates the number of messages that have been recorded on the ICM tape Dis crete LEDs are often used for this purpose In normaloperation a typi cal indicator may be on constantly when there are no messages After an ICM has been recorded the LED be gins to blink In some machines the LED blinks
200. rer Address 6 watts 1 year 1 195 Telephone Among the features of this modem is support for five error correction meth ods MNP Classes 2 through 4 V 42 and optional V 32 trellis encoding With MNP and V 42 error correction the data packet is checked for accuracy using a parity bit MNP Class2 or a CRC check sum MNP Classes 3 and 4 and V 42 If an error occurs the faulty data is discard ed and a replacement data packet is sent Trellis coding on the other hand adds a special forward correcting data bit to the byte that tells the receiver how to correct errors in the data packet by itself thus saving time and further improving throughput because data re transmission isn t needed With either method the Model 9632VP constantly monitors the phone line for quality If line conditions are so poor that there are more errors than data coming down the pipe V 32 automatical ly throttles the modem back to 4 800 bps During the fall back period the modem makes periodic attempts at re establish ing 9 600 bps communications Unlike most modems the Model 9632VP doesn t use mechanical DIP switches for its hardware configuration MNP 2 4 V 42 compliant Hayes AT Racal Vadic ATPlus 25 pin RS 232 2 4 lbs with power transformer Racal Vadic 1525 McCarthy Blvd Milpitas CA 95035 408 432 8008 Instead the hardware instructions are entered from the keyboard and stored in nonvolatile memory However the fro
201. s etc In addition to the foregoing the con version unit will also calculate how many BTU Hour units an air conditioner would have to produce to cool the room properly or BTU Hour for heating In use the Home Contractor per formed just about how one would expect it to However it was disconcerting at first to discover that an LCD reading dis appeared in short order The operator guide notes indicated that it does this to conserve battery life three replaceable lithium batteries with an estimated one year plus life Pressing a Recall button restores thereading though but it is still a minor bother A second in use revelation was that I dislike soft keys You ve got to press too hard to get it to work A third and final criticism is that the ultrasonic activation switches at each side of the device are in a location where one s fingers seem to naturally press when handling it This is compounded by the switches being espe cially sensitive a light touch sets it off AS you can see trying out a product is especially important In this case I m talking about a unique product of course which with its minor shortcom ings is still an impressive device A hands on approach becomes more important when there are competitive models out there of course So whenever you can do make an effort to operate a device be fore buying Most storekeepers will cooperate Ate Say You Saw It In Modern Electronics W LETTER
202. s games tech files ham radio etc The BBS supports TTY and ANSI color terminals connecting at 300 1200 or 2400 bps plus 9600 bps HST and V 32 connections The BBS access numbers are 408 559 0253 for 9600 bps it s 408 559 0297 or 0298 NEW ELECTRONICS TRADE ASSOCIATION Installers of entertainment systems and other home electronics devices formed a new national trade association to promote the profession and develop service standards It s estimated that custom installation of home electronics electronic equipment for media rooms whole home entertainment systems home automation systems etc is a 250 million business and growing rapidly Companies seeking CEDIA Custom Electronic Design amp Installation Association membership must show compliance with federal state and local laws all applicable licensing and insurance requirements including liability worker Sec e ae and bonding in their marketing area Additionally the company must have been in business using the current company name for at least two concurrent years preceding membership application and has to submit names of three industry references such as manufacturers sales organizations or other installers Contact CEDIA 10400 Roberts Rd Palos Hills IL 60465 Phone m dto uh NEW LA FM SIGNAL A powerful Los Angeles radio statipn KROQ FM now broadcasts an additional signal paging messages to business travelers on the unused portion of the station
203. s portion of the system simply condi tions the speech signal from the mi crophone and sends it to the switch ing network 11 Speaker Amplifier This is an audio power amplifier that drives the answering machine s speaker from the switching network Machine Operation The modern telephone answering machine operates in a very orderly and logical manner The procedure is as follows e Picking Up the Line A 90 volt ac 20 Hz ring signal is sent from the telephone company s central office to the called telephone instrument whenever a connection is made to the line to signal an incoming call Fig 2 The Ring Counter circuit in the answering machine detects the ring signal and generates a counting pulse for each series of rings Virtually all machines are equipped with a RING SELECTOR switch that can be set to al low a certain number of ring cyclesto pass before it enables the Pickup Cir cuit Fig 1 Typical settings for this Ring detector ANSWERING MACHINE Ring counts Pickup command Ring counter Ring selector Switch switch are for two rings four rings and Toll Saver Toll Saver is a clever feature that lets the line ring four times before making a connection when there are no messages and only twice when there is at least one recorded mes sage This is handy when making a toll call to check on messages by re mote because you can hang up the handset after the second ring if the
204. s a Y connector that pulls power from the keyboard connector though if this doesn t supply enough power to run both your keyboard and the WIZ you can buy an optional power supply Once this hookup is made you need to plug both the cable from the mouse de vice and from the PC s serial port into the tablet These connectors aren t keyed and the documentation doesn t really show how they get plugged in It is possible to plug the cable in the wrong fact it seems to go in easier the wrong way though doing this did not seem to damage the unit Another area in which the documenta tion falls short is in performing the soft ware installation for Windows It just tells you to reinstall Windows selecting other device for the pointing device choice and inserting the WIZ utility disk when prompted What is not stated is that the Windows SETUP utility requires 512K of free RAM to work If you are us ing a 640K system and have installed the DOS drivers for WIZ you won t have enough memory to complete SETUP it just dies in the middle with an error message The solution is simple You have to re name the CONFIG SYS file the DOS set up routine creates reboot the PC and complete the Windows SETUP Then go back and rename CONFIG SYS so that it loads the correct drivers for the WIZ A better way would have been to just warn the user to do the Windows SETUP first Once installed though the WIZ worked the way it s s
205. speed pause delays wide narrow FM reception and high frequency stability Options C R7000 RC 12 remote control EX 310 voice synthesizer CK 70 DC adapt r MB 12 mobile bracket IC R71A RC 11 remote control EX 310 voice synthesizer CK 70 DC adapter MB 12 mobile bracket FL 32A 500Hz FL 63A 250Hz and FL 44A filters See these quality ICOM receivers at your local authorized ICOM dealer today lS al the C R7000 guaranteed from 25 1000 Hz and 1260 1300M Hz No coverage from 1000 1025MHz ICOM America Inc 2380 116th Ave WA 98004 Customer Service Hotline 206 454 7619 3150 Premier Drive Suite 126 Irving TX 75063 1777 Phoenix Parkway Suite 201 Atlanta G 30349 ICOM CANADA A Division of ICOM America Inc 3071 5 Road Unit 9 Richmond B C V6X 2T4 Canada All stated specications re subject 10 Change without notice or obiigallon All radios signiicanily exceed regulations limiting spurious emissions 9 89 Oo ICOM First in Communications Discover Your Career Potential In High Tech Electronics Call 1 800 776 1900 CIE Gives You The Training You Need to Succeed At Your Own Pace amp In Your Own Home you re anxious to get ahead and build a real career you owe it to yourself to find out about the Cleveland Institute of Electronics CIE can help you discover your career potential in the fast growing field of high tech
206. square wave response tests can be made using a function generator at the signal source Although dc voltage and resis tance measurements are basic and valuable they do not spot open capacitors and do not indicate the presence of shorted turns or layers in inductors To cite a familiar proce dure a yoke with a few shorted turns can be effectively checked with a pulse generator and oscilloscope though the yoke on a TV picture tube will appear to be okay if only resis tance tests were made ME March 1990 MODERN ELECTRONICS 49 WWNW americanraciohlstorv com Project A Pocket Snooze Alarm Lets you catnap for selected periods of 5 I0 15 or 30 minutes before being awakened by the battery powered alarm By Homer L Davidson aking a short nap after lunch or whenever you feel dragged out can do wonders in keep ing you alert later when it counts Sometimes just closing your eyes for 10 or 15 minutes can let you relax enough to speed through your next job And pulling off the road during amp long haul to relax for a vital few minutes can prevent an automobile accident There are any number of situations in which a short nap can be beneficial One way to help you get your short nap but not sleep through several hours is to have handy a small Snooze Alarm like the one described here to wake you This pocket size battery powered Snooze Alarm can be used anywhere on a driving trip to your Off
207. t sees a moderately high Q RLC network It does not make any difference what the cause of the rising high fre quency response may be For exam ple it can be caused by deteriorated emitter bypass capacitors The prac tical result is that the amplifier net work now contains pseudo induc tance which evaluates as an RLC peaking network As a helpfui rule of thumb any RLC network that contains more than one section with Q values that are greater than 1 will ring most pro minently at the sectional frequency that has the highest Q value If a multiple stage amplifier has stages that have uniform frequency re sponse the overall frequency re sponse will be flat and the ampli fier will have little tendency to over shoot and ring on a square wave test However even when overall fre quency response i5 uniform the am plifier will overshoot and ring if it has a rapid high frequency rolloff char Say You Saw It In Modern Electronics Current t3 Time Overshoot volts Time B Current C Fig 6 Square wave overshoot and ringing modes A critical damping where Q is 1 and overshoot is a single surge B where Q is slightly greater than 1 and overshoot is followed by a half cycle of ringing C where Q is comparatively high and overshoot is followed by a substantial ringing sequence acteristic This is a consequence of nonlinear phase response
208. t exceed 7 inches A longer antenna violates Part 15 122 field strength restrictions The transmitter can be tuned with the help of a vhf receiver a Spectrum Probe or both Firstly temporarily disconnect the collector of Q2 from the circuit to permit the r f oscillator to operate con tinuously in CW continuous wave mode Then apply power to the transmit ter and tune the radio receiver until a strong continuous tone is heard If the signal frequency is near that of a local ra dio station alter the transmission fre quency of the transmitter Transmission frequency can be altered by varying the position of the tap or by slightly com pressing or stretching the coil Another way to tune the transmitter is to slightly increase the value of C5 This can be done by adding one or more 1 pi cofarad capacitors in parallel with C5 Alternatively you can replace C5 with a miniature variable capacitor like those used in digital watches and miniature r f gear If you use a variable capacitor it s imperative that you use an insulated alignment tool to change its setting Still another way to tune the transmit ter is to replace R6 and R7 with a 10 000 ohm potentiometer Adjust the setting of the pot to center of rotation Slight changes in position of the wiper change the oscillation frequency slightly See Electronics Notebook April 1987 for more details about the transmitter Testing the Transmitter With the Spe
209. t particular remote The Control Circuit in the machine compares the code to the code in its memory When a code match is obtained the answering ma chine stops and resets the OGM then rewinds and plays back the ICM tape and transmits any recorded messages back to the calling instru ment over the telephone line Fig 7 The caller hangs up after the last message is played back and the ma chine immediately disconnects from the line and resets itself to be ready to record the next incoming call message If the remote controller and an swering machine codes do not match the machine will complete the outgo ing message and record the incoming message in the normal manner sim ply ignoring the remote controller In some machines the codes for the re mote and machine are fixed In many other models however code selector switches permit the user to enter the Speaker sSpeaker P amplifier ICM play Drive motor Motor M driver 1 Caller dials the desired number 2 3 C O rings the desired Machine picks up and line plays outgoing message Central office C O T Answering machine AW Dial pulses Ring signal 4 Caller presses 5 playback to send Codes match code to machine OGM stops and ICM Remote plays for caller control a Central office ng 1 C O machine 1357 2 1357 1357 Fig 7 When using remote control t
210. ter kits and electronic components is now avail able The 84 page catalog lists and fully describes a wide variety of computer kits and related products as well as integrated cir cuits and other semiconductors It also lists capacitors resistors switches connectors project enclosures tools and tool kits and more separate section is devoted to test instruments and in cludes listings for oscilloscopes meters logic probe and 1 GHz frequency counter Included in the computer products line up are an 80286 laptop computer 80386 and 80286 computer kits 80386 and 80286 full size and baby AT motherboards expansion cards monitors and floppy and hard disk drive systems Accessory products include internal and external modems desktop and tower computer cases power supplies printers software handheld scanners printer and monitor stands keyboards and keyboard drawers etc Fora free copy writeto Jameco Electronics 1355 Shoreway Rd Dept ME Belmont CA 94002 Say You Saw It In Modern Electronics 386 FULL 32 BIT COMPUTER AND VGA COLOR MONTOR 100 IBM compatible 32 bit 80386 microprocessor 8 16 MHz speed switchable 40 MB 22 millisecond hard drive w integral 1 1 interleave controller One MB RAM expandable to 8MB 5 25 1 2 MB floppy disk drive Four 16 bit expansion slots Two 8 bit expansion slots One 16 bit VGA video adaptor w 256K memory expandable to 5
211. term prog for the PK232 18 disk 1143 KAM RTTY dedicated RTTY CW AMTOR ASCII terminal program for TNC s 18 disk 1250 World Atlas a top information atlas 20 disks 200 201 WAMPUM dBase 3 clone 1 800 525 7235 to order Visa MC 9 5 CST or send check MO add 3 00 s h call 205 757 5928 or write for free catalog Renaissance Software Library Box 640 Killen AL 35645 CIRCLE NO 122 ON FREE INFORMATION CARD PC CAPERS small powerful and affordable Chances are that they not only will be but will be available fairly soon The WIZ Back about a year and a half ago I re viewed a device called Felix which was a replacement for a mouse It was an inter esting device that failed to garner much interest among purchasers and seems to have passed to the category of de vices that never quite made it The mouse has become an almost universal pointing device spurred on to a large ex tent by software such as desktop pub lishing CAD and even Graphical User Interfaces called GUI or gooey which make good use of its ease of cursor positioning function This year s COMDEX featured several trackballs which are essentially sta tionary upside down mice I find this de velopment interesting and in a sense counter evolutionary because trackballs were used first This to the fu ture development seems to indicate that as popular as m
212. times out and causes the machine to disconnect Many current machines build a VOX function into their fixed times With this arrangement a 30 second duration selection will cause the machine to record an ICM for 30 seconds or until the caller stops talking for a few seconds whichever comes first The number of messages that can be recorded on one side of a tape de pends on the length of the tape and the selected recording duration If a 60 minute 30 minutes per side cas sette is used and a 2 minute time limit is chosen the minimum number of messages that can be recorded on one side of the incoming message tape is 30 2 or 15 messages e Disconnecting Modern telephone company central office facilities us ually have a Calling Party Control CPC circuit When the caller hangs up thetelephone a brief interruption in the called party s telephone circuit is generated by the central office This break can be short about 10 milliseconds or long about 350 mil liseconds A machine with CPC con trol will disconnect on that signal The switch on an answering machine usually has LONG and SHORT duration positions Fig 5 that allow for differences in central office equipment If the length of the central office CPC signal is unknown it is usually a good idea to initially set the machine s CPC switch to the LONG position If the line is equipped with Call Waiting it may be neces sary to leave the CPC switch set to LO
213. ting for the metering circuit when the cur rent monitoring function is selected If you wish to incorporate into your bench power supply a fixed 5 volt output you can use of a number of regulated supply designs You can find schematic diagrams for these in a wide variety of electronics magazines and books Use of a separate 5 volt supply re quires a third power transformer that connects directly across the in coming ac line Install a separate 5V POWER switch to enable and disable this supply as needed as well as a separate LED indicator to inform you when this auxiliary supply is on and off If you go this route be sure to include a separate fuse of appro priate rating in series with the 5 POWER switch and primary lead of the new power transformer Construction There is nothing critical about com ponent placement or conductor runs Therefore you can use any wiring technique that suits you to build the project For example if you wish you can design and fabri cate a pair of printed circuit boards on which to mount the basic power supply circuitry and the metering cir cuitry Otherwise use perforated board that has holes on 0 1 inch cen ters and suitable Wire Wrap or sol dering hardware Whichever way you go be sure to use sockets for the two DIP ICs and LED numeric displays Wire first the basic power supply circuit and then the metering circuit and its power supply on boards that are as small as
214. tion of all six latches Once you verify operation of each stage power down the project and remove the wires from the 5 volt bus and pins of 166 through 1 11 and remove the LED resistor combinations Plug the six LED displays into a solderless breadboarding socket to precheck all seven segments of each before installing the displays in their sockets Connect the common cath odes of the displays to the ground bus in the project Tack solder a suit able length of hookup wire to the 5 volt bus in the project and ter minate the other end of the wire ina 330 ohm resistor Use this test lead to check each segment in each dis play by plugging the free lead of the resistor into the appropriate holes for the pins that connect to segments a through of each display 2N3904 Fig 6 A circuit for testing operation of project s transistors out of circuit You can also check each of the Q7 through transistors out of cir cuit To do this breadboard the cir cuit shown in Fig 6 The transistor shown here is the one that will be in stalled in the project This test circuit is designed to prevent exceeding the maximum allowable base current for the transistors You verify operation of the tran sistor under test by powering up the project closing the switch and ob serving the LED If the LED lights with the switch closed the transistor is good If the LED does not light discard the transistor and replace it wit
215. tional AT9N HO 10 1 Primary 600 ohm T Kp Secondary 600 600 ohm 1 0 77 X0 61 0 67 high f 6 p c pins on 0 187 centers Primary Inductance 300 mH min at 1kH2 1 voit CAT TCTX 1 1 25 each 10 for 11 00 ORDER TOLL FREE 1 800 826 5432 MAIL ORDERS TO ALL ELECTRONICS P O BOX 567 VAN NUYS CA 91408 Button extends 3 16 above switch body CAT GRABMS 2 00 per package NPN and PNP Some house 1 marked some standard marking CAT GRTRN 2 00 per assortment SWITCHES A 10 assorted slide f5 L toggle rotary pushbutton is and rocker switches Our choice CATS GRABSW 2 00 per assortment INFO 818 904 0524 FAX 818 781 2653 MINIMUM ORDER 510 00 QUANTITIES LIMITED CALIF ADD SALES TAX USA 3 50 SHIPPING FOREIGN ORDERS INCLUDE SUFFICIENT SHIPPING NO C O D A C LINE CORDS Black 6 18 2 SPT 2 NON POLARIZED PLUG CAT LCAC 2 for 1 00 100 for 45 00 TO 92 TRANSISTORS 20 assorted TO 92 plastic case transistors Various stytes of POLARIZED PLUG LCP 1 604 each 100 tor 50 00 CIRCLE 120 ON FREE INFORMATION CARD WWW americanradiohistorv com DIGITAL VIDEO STABILIZER ELIMINATES ALL VIDEO COPYGUARDS While watching rental movies you will notice an noying periodic color darkening color shift un wanted lines flashing or ja
216. to send data in excess of the baud rate PSK modulation uses two oscillators running at 90 degrees apart for its digital encoding According to the value of the binary bit the encoder chooses between one of the two oscilla tors at predetermined intervals to pro duce a waveform like the one you see in the waveform drawing A phase locked loop PLL detector in the receiving mo dem decodes the phase information As the speed of the modem increases so does the complexity of the carrier waveform because the phase must be changed more times per cycle to accom modate the faster data rate At 2 400 bps each 1 200 Hz carrier cycle experiences four phase changes which is simple enough to decipher However when a 1 200 Hz carrier is encoded for 9 600 bps it s nearly impossible to distinguish the 16 phase changes per carrier cycle from the random background noise com monly found on telephone lines The only recourse is to make the carrier waveform simpler by increasing the carrier frequen cy But if this is done there isn t enough bandwidth for two separate carriers which means that a new approach must be found The V 32standard forged by the Coop erative Committee for International Tel ephone and Telegraph CCITT meets the challenge using a technique called cancellation In echo cancella tion two modulated 2 400 Hz carriers are put onthe phone line at the same time One carries your data and the other
217. tors 56 9000 129 RF Freq 100K 450MHz AM Modulation of 1KHz variable RF output 56 9500 with Digitai Display and 150MHz built in Freq Cir 249 Digital Triple Power Supply 765 249 0 20V at 1A 0 20V at 1 5V at 5 Fully Reguiated Short circult protected with 2 Limit Cont 3 Separate suppiies _XP 660 with Analog Meters 175 F 100 120MH 179 F 1000 1 2GH Frequency Perlod Totalize 259 Self Check with High Stabilized Crystal Oven Oscillator 8 digit LED display WE WILL NOT BE UNDERSOLD UPS Shipping 48 States 5 10 Max IL Res 7 Tax M 4500 3v digit 125 4 digit 175 o 69 95 AUDIO GENERATOR 600 ohm Output Impedance High Output Voltage Quad Power Supply Fully regulated and short circuit protected XP 575 55 1500 Reads Volts Ohms Digital Capacitance Meter HR 1550 ms 2 58 95 9 Ranges 1pt 20 000ufd 5 basic accy Zero control Muitimeter with Capacitance and Transistor Tester LC urrent Capacitors Res 01 iodes with case AC Current Meter ST 1010 69 95 1000 Amps Data amp Peak Hold 8 Functions Deluxe Case Current A All have color coded posts Temperature Probe M 110CF 29 95 Semiconductor type 302F S 3000 i 275 10MHz DC or AC Triggered Sweep m Calibrated Vert amp Hor E Reads Volts amp Freq digital multimeters Function Generator Esc Blox
218. uency access via their front keypad main tuning dial optional infrared remote control and or computer interface adapter Incredible Flexibility Full Coverage Maximum Performance The superb IC R71A is your key to world wide SSB CW RTTY AM and FM optional communications plus foreign broadcasts in the 100kHz to 30MHz range It features IF Notch low noise mixer circuits and 100db dynamic range The pacesetting IC R7000 receives today s hot areas of interest including aircraft marine public services amateur and satellite transmissions in the 25MHz CIRCLE 13 ON READER SERVICE CARD to 2000M Hz range It includes all mode operation low noise circuits plus out standing sensitivity and selectivity The IC R71A R7000 combination is your window to the world The IC R71A is a shortwave listener s delight Its 32 tunable memories store frequency and mode information and they aresingle button reprogrammable independent of VFO A or VFO B s operations Dual width an adjustable noise blanker panel selectable RF preamp and selectable AGC combined with four scan modes and all mode squelch further enhance the IC R71A5 HF reception The IC R7000 features 99 tunable memories and six scanning modes It even scans a band and loads memories 80 to 99 with active frequencies without WwWW americanradiohistory com a A A E MEMORY CH 6 6 operator assistance Additional features include selectable scan
219. upposed to It salot of fun to use At a price of 249 95 it sa bit more expensive than a standard mouse though it is quite a bit less expen sive than a digitizer If you do much drawing and or CAD work the WIZ is something you will wanttolookat Age Products Mentioned Compaq 286 LTE Compaq Computer Corp Box 692000 Houston TX 77269 713 370 0670 WIZ CalComp 2411 West La Palma Ave Anaheim CA 92801 800 CALCOMP or 714 821 2000 CABLE TV DESCRAMBLER Jerrold S B Jerrold SB w Trimode Oak N 12 w VS Scientific Atlanta Pioneer We Beat Anyone s Price 30 Days Money Back Guaranty Free Catalog Visa M C COD or send money order to US Cable TV Inc Dept KAJ 4100 N Powerline Rd Suite F 4 Pompano Beach Fl 33073 1 800 445 9285 Please have make and model number of the equipment used in your area ready No Florida Sales It s not the intent of US Cable TV Inc to defraud any pay TV operator and we will not assist any company or individual in doing so PACKARD BELL mas Armerica prew up fete fer ars df still dues PACKMATE 286 COMPUTER WITH VGA COLOR MONITOR 80286 microprocessor operates at 12 MHz One 3 1 2 1 44 MB floppy drive One 5 1 4 1 22 MB floppy drive 30 MB hard drive t MB RAM on mother board expandable to 3 MB Includes VGA 14 color monitor amp VGA card High res monitor 480 x 600 amp 256 colors compatible gt AT compatible 8 expansi
220. urst once every 10 seconds at a fre quency within the 88 to 108 MHz FM broadcast band In operation QJ L1 and C5 make up the transmitter s oscilla CIL LI n RR CU RE Lala ao c CER LEE a ES 62 MODERN ELECTRONICS March 1990 WWW americanradiohistorv com Say You Saw It In Modern Electronics tor Configured as an oscillator modulates the r f carrier with an audio tone that has a frequency that s con trolled by the values of R7 and Inter val timer C2 enables the r f oscillator for 0 25 second at 10 second intervals Each time the transmitter broadcasts a tone burst the LED glows The principal purpose of this LED is to drop the volt age applied to the r f oscillator to around 1 5 volts to keep the output power from the transmitter within guidelines set forth in Part 15 122 Oscillator coil 1 1 is the most impor tant component in the Fig 4 circuit This is an air core coil that s made by wrap ping five turns of solid wire around a inch form When the form is removed the coil springs outward slightly and as sumes a diameter of about inch The tap in my original transmitter was merely a wire soldered at the midpoint of the coil As result of the tests that follow I replaced the soldered tap with the small clip lead shown in Fig 5 Connected to the junction of LZ and the collector of the length of the transmitter s antenna shouldn
221. us motors from either a 12 volt dc or 117 volt ac power source The project produces up to 300 milliamperes which is enough current to drive several small motors simultaneously Frequency adjust ment is accomplished with a potenti ometer and either an external fre quency counter or a clever beat fre quency display that especially simpli fies calibration of the power supply at frequencies close to 60 Hz Although in this article we will concentrate on using the power sup ply which comprises the major por tion of the project in a Tide Clock application there are many other uses for it These include operating small appliances and powering a tele scope drive motor for stargazing 5 tronomers should appreciate the var iable frequency control the project affords allowing them to temporari ly convert from solar drive to sidereal tracking Making of a Tide Clock Our Tide Clock works on the as sumption that there are two equal tidecycles per day each comprising a high and alow tide For all but a few locations on Earth where coastal features cause irregular tide inter vals this is a valid assumption Most areas on Earth can be repre sented as discrete points on a rotating globe that pass through two high and two low tides with every revolution Locations of the high and low tides are fixed by the moon If the moon stood still each revolution of the lighthouse depicted in Fig 1 would take 24 hours exactly and an
222. utorial and supplies BASIC programming tutorial Printed circuit board layout Video display adapters for PCs techniques Laser printing Making printed circuit boards Surface mount technology Electrical safety Basic radio Basic TV Solid state darkroom timer Electrical surge protection Amplifier for your Walkman Basic telephone Telephone testing set Cellular telephone Night light that turns on when telephone rings our PC General diagnostic techn Ground fault interrupter Soldering iron idler performance 5 Plug it in end use it Build your understandin ground up Learn the technology Digital logic fundamentals Installing accessory cards in y Installing a hard fixed disk drive Managing data on your hard drive Electrical desoldering techniques Audible voltage continuity tester Cost effective function generator Double sided printed circuit boards Improving antenna reception awe when you can fix it yourself Save lex Your Manual gives you listings of firms that sell electronic components through stores and through the mail unneeded service calls 4 Sources of supply 5 Professional hints and kinks tips amp new techniques Professional techniques are explained in detail iu You learn the easy shortcuts as we out for as the pitfalls to 6 Keep on top of what s new Advances in electronics occur rapidly so we send regular updates to give you ins
223. volt electrolytic C4 1 4F 2 volt electrolytic Resistors 5 watt 5 tolerance RI thru R7 33 ohms R8 1 megohm R9 100 060 ohms Miscellanecus J1 J2 16 pin DIP IC socket T1 12 6 volt l ampere power transformer Printed circuit board or perforated board with holes on 0 1 inch centers and suitable Wire Wrap or soldering hardware see text sockets for all DIP ICs and LED displays two 16 conductor ribbon cables with 16 pin headers suitable enclosure LEDs 330 ohm resistors CD4060 divider chip and spst switch for testing pur poses see text machine hardware hookup wire solder etc Note 746917 display controller driver is available by mail order from Digi Key P O Box 677 Thief River Falls MN 56701 9988 or Jameco Electronics 1355 Shoreway d Belmont CA 94002 Fig 3 Schematic diagram of all cir cuitry except power supply used in the project Say You Saw It In Modern Electronics WI 85 6 0902 221 005194 51 3 935 99510 1951 4M 06 S71b4 St ELIS TL 1121 621 6 91 THE ee 4157194 ELIS THL ELIS THL ELIS Ved 4lS7 54 ee aim 5 5 ecco MIRI or wo i tno 72 March 1990 MODERN ELECTRONICS 4i Say You Saw It In Modern Electronics Master Wiring List From Pin OO 3 AM
224. w its easier than ever to incorporate single chip microcomputers in your new designs The MCPM 1 system allows the IBM PC and compatibles to be used as a complete development system for the Motorola MC68705P3 P5 U3 U5 R3 and R5 single Chip microcomputers The system includes a Cross assembler program simulator debugger program and a programming board that connects to a serial port Price 449 00 VISA and MASTERCARD accepted TECI THE ENGINEERS EC oui INC RR 3 BOX8C Barton Vermont 05822 Phone 802 525 3458 FAX 802 525 3451 CIRCLE NO 144 ON FREE INFORMATION CARD MODERN E MART Classified Commercial Rates 1 per word 15 word minimum 15 00 prepaid Worc count includes name and address ZIP code and abbreviation each count as one word P O Box number and telephone number count as two words each Indicate free cate gory heading Computers Communications Electronics Video or Miscellaneous A special heading is available for a 6 surcharge First word only is set boldface caps at na charge Add 20 for additional boldface words Non Commercial Rates FREE to subscribers as space permits maximum 15 words A recent MODERN ELECTRONICS mailing label must accompany ad All advertisers with P O Box addresses must supply permanent address and telephone number Copy is subject to publisher approval Mailing Information Copy must be received by the publisher by the 25th of the third month preceding the c
225. wo years 147 00 three years 219 00 Entire contents copyright 1990 by CQ Communications Inc Modern Electronics or CQ Communications Inc as sumes no responsibility for unsolicited manuscripts Al low six weeks for delivery of first issue and for change of address Printed in the United States of America Postmaster Please send change of address notice to Modern Electronics 76 North Broadway Hicksville NY 11801 CQ Communications Inc is publisher of CQ The Radio Amateurs Journal Popular Communications Modern Electronics CQ Radio Amateur Spanish CQ and the CQ Amateur Radio Buyer s Guides Say You Saw It In Modern Electronics CABLE TV ITEM HAMLIN 3000 36 CORDED REMOTE PANASONIC WIRELESS CONVERTER 10 OR MORE ONVERTER m 29 00 18 00 r best buy 98 00 79 00 MOVIE TIME VR7200A manual fine tune 88 00 69 00 JERROLD 400 COMBO 169 00 119 00 JERROLD 400 HAND REMOTE CONTROI 2900 8 00 JERROLD 450 COMBO 199 00 139 00 JERROLD 450 HAND REMOTE CONTROI ERROLD SB ADD ON 29 00 18 00 99 00 63 00 JERROLD SB ADD ON WITH TRIMODE 10900 75 00 M 35 B COMBO UNIT Ch 3output only 99 00 27000 M 35 B COMBO UNIT WITH VARISYNC 109 00 75 OC MINICODE iN 12 99 00 00 MINICODE iN VITH VARISYNC MINICODE VARISYNC WITH AUTO ON OFF 145 00 ECONOC ODE imi
226. xA 9600 28 95 Provides sine tn sgu wave trom 1 2 10 1MHz AM of FM Capability 56 9200 129 Low distortion lt 05 10 1MHz Sine Square Wave 4 pt to 10MFD XP 580 59 95 2 20 2A 12V at 1 5V at 3A 5V at 5A withaut meters 39 95 14 Transistors 5 Diodes with Freq Counter Decade Blox 9610 0r i 9620 Digital LCA Meter 1801 125 Measures Coils tuH 200H Caps 1 2000 20M AC Clamp On eel Buroinging DMM 5000 545 9 Functions 3 digit LCD 18 95 9610 Resistor Blox 47 ohm to 1M amp 100K pot 9620 Capacitor Blox AM FM TRANSISTOR RADIO KIT with TRAINING COURSE Makes a great School project Model AM FM 108 26 95 Circuits are laid out in systematic order on an over sized PC board for easy understanding of the flow 249 Sine Square Triangle Pulse Ramp 2 to 2 2 Freq Counter 1 10MHz GF 8015 without Freq Meter 179 C amp S SALES INC 1245 Rosewood Deerfield IL 60015 800 292 7711 708 541 0710 CIRCLE NO 140 ON FREE INFORMATION CARD WWW americanradiohistorv com of radio signals from antenna to speaker Complete course includes all parts PC board and training manual When completed you will be proud to dis play your masterplece T Transistor AM RADIO KIT 16 95 15 Day Money Back Guarantee 2 Year Warranty WRITE FOR FREE CATALOG Prices subject change Technology lelephone
227. yone in the lighthouse would see the tide change every 6 hours If this were the case an ordinary clock could be used to tell when the high and low tides would occur However because the moon revolves around the Earth in the same direction as the latter is ro tating each revolution of the light house with respect to the tides takes 25 hours and 50 minutes Project A Tide Clock Keeps track of the rise and fall of water affected by ocean tides By Joseph P O Connell One way to represent this cyclical event is with a specially designed syn chronous motor that makes one rev olution every 12 hours and 25 min utes Using this approach two revo lutions of the motor would be needed to complete every cycle of four tides This approach makes it easy to use a clock face arrangement with a single hand to point to the condition of the tides depicted on the face of the clock at any given moment for a giv en location Another approach to obtaining the same effect is to drive a standard clock motor at a slightly lower fre quency than the 60 Hz of the stan dard ac line With proper selection of drive frequency the hours hand will complete one revolution around the dial face in 12 hours and 25 minutes instead of the usual 12 hours Rather than being fixed to either an ac or a dc power source our Tide 7 Say You Saw It In Modern Electronics March 1990 7 MODERN ELECTRONICS 31 eeoleal ialalale fallelal

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