SAMII Manual
Contents
1. 5 1 3 1 6 START STOP Push button In AUTO mode the START STOP push button forces all contents of the internal buffer to be output and recorded to tape In this mode the recorder automatically switches on and a buffer dump occurs whenever the internal buffer is full If 15 minutes elapses without such an automatic dump a forced buffer dump takes place Therefore at the end of an operation the buffer could contain some collected speech Thus the START STOP push button should be pressed prior to either changing tapes or terminating a record session to avoid the loss of this collected speech In MANual mode the START STOP button is used to manually toggle the state of the recorder between recording and standby The unit s 15 second buffer is disabled in this mode 3 1 7 AUDIBLE ALARM Switch The AUDIBLE ALARM switch is used to enable or disable the speech activity alarm This alarm follows the activity of the SPEECH ACTIVITY LED The alarm buzzer can be permanently disabled by removing Jumper 1 JP1 on the main board of the unit This may be desirable if the unit is to be installed in a sensitive area 3 1 8 CALIBRATE Push button The CALIBRATE push button is used to output a 6 dBV 814 Hz tone to both output channels of the SAM II and thus to the tape recorder inputs This tone is the loudest audio producible by the SAM Il and should be used to set the record level of the tape recorder typically OVU At this setting it should be2. impossible for the SAM Il to overload the recorder 3 2 REAR PANEL Connectors f CAS S N SAM2 MADE IN USA INPUT OUTPUT RELAY L R L R ji GND E p AG on roy 12VDC L L 500mA Figure SAM II Rear Panel 3 2 1 INPUT and OUTPUT Connectors Left and Right INPUT and OUTPUT jacks are Phoenix type connectors with supplied terminal strip plugs Wiring of these plugs is required by the user upon installation see Figure 4 The output connectors have a nominal 6 dBV output level The input connectors accept audio over a range 11 to 9 dBV These audio jacks can accommodate balanced differential or unbalanced single ended line level signals 3 2 3 RELAY Connector This Phoenix type connector provides the normally open NO normally closed NC and common COM terminals of the internal relay and is used for automatic tape recorder control Operation of the relay follows the RECORD LED when the RECORD LED is on the NO and COM terminals will be connected and the NC terminal will be open circuited When the RECORD LED is off the NC and COM terminals will be connected and the NO terminal will be open circuited For most portable cassette recorders the NO COM pair would be wired into a 2 5 mm phone plug and connected to the recorders REMOTE jack for proper operation 3 2 4 DC POWER The SAM requires 9 18 VDC power 2 1 mm barrel connector w
3. is internally protected against reverse polarity and includes resettable fuse special external overcurrent protection is required The SAM may be wired directly to a 12 VDC electrical system or alternatively may be powered by either 115 VAC or 230 VAC 50 60 Hz utilizing the universal AC power adaptor included Connection is via a 2 1 mm barrel connector with center conductor positive and sleeve ground 13 5 1 Setting Internal DIP Switct The internal DIP switch block enables the user to customize the amount of PRE BUFFER delay on the output of the SAM Il tailoring it for specific recording situations and tape recorders In most applications no delay is needed which is the default factory setting However when using rotary head external recorders such as DAT or VHS machines up to 7 seconds of delay may be required to give the tape time to be loaded and the record head engaged without losing speech The locations of the DIP switches are shown in the Circuit Board Layout of Figure 5 Table 1 shows the four delay amounts possible in the SAM II and the DIP switch combinations used to achieve them Table 1 PRE BUFFER Delay Configuration Amount Oe OFF OFF ON 1 OFF OFF 3Seconds Note 1 DIP Switch 1 is used to activate special diagnostics mode and should always be set to the OFF position unless directed otherwise by a DAC technical support
4. second buffer by the buffer control logic When the 15 second buffer is nearly full the buffer control logic activates a record sequence consisting of the following steps 1 The tape recorder is switched on for a predetermined PRE BUFFER TIME The This step allows adequate time for the recorder to come up to speed before audio is output by the SAM 2 Audio from the buffer is recorded on the tape If the SAM Il is currently collecting speech this step is continued until the buffer is completely empty 3 A silence of Tps the POST BUFFER TIME is recorded as a trailer This silence period permits as occurs with certain DAT recorders the next record startup to back up over a brief segment of the previous recording without destroying collected speech The POST BUFFER TIME is set to 0 5 seconds on the SAM Il The SAM Il will automatically dump its buffer contents to the recorder if no dump has occurred for 15 minutes This feature minimizes losses should power or instrument failure occur Also this dump may be forced manually initiated with the front panel START STOP push button This button is pressed at the end of an operation to clear out a partially filled buffer before powering down the equipment 3 0 CONTROL AND CONNECTORS The SAM Il is controlled by front panel push buttons and slide switches An internal DIP switch enables the user to select the appropriate PRE BUFFER TIME delay for the type of recorder being used All signa
5. Connect the SAM Il to the tape recorder as specified in Section 4 1 and activate RECORD on the tape recorder Press the SAM II s CALIBRATE push button and adjust 10 SAM II Rear Panel INPUT OUTPUT RELAY R Microphone Preamplifier Microphone Portable Cassette Recorder SAM II Rear Panel OUTPUT RELAY L NO NC COM Microphone Preamplifier Professional Stereo Cassette Recorder Microphones Figure 4 SAM II System Connections 11 the record level control s on the tape recorder for an indicated level of OVU Once the level has been adjusted release the CALIBRATE push button 4 2 3 Selecting AUTO or MAN Recorder Control If the SAM Il is being used in an unmanned surveillance operation set the RECORDER CONTROL switch to AUTO then verify that as speech is detected and accumulated into the 15 second buffer indicated by the SPEECH ACTIVITY LED the recorder turns on at least once every 15 minutes or more frequently if there is a lot of speech activity For manned surveillance operations set the RECORDER CONTROL switch to MAN then verify that the recorder toggles on and off as the START STOP pushbutton is pressed 4 2 4 Arming Tape Recorder for Record Operation For many analog cassette tape recorders the SAM II s RELAY jack will be connected by cable to the 2 5 mm REMOTE control jack on the recorder Activating the record mechanism generally requires pushing down the RECORD and PLAY buttons simultaneously
6. SAM II Speech Activity Monitor with Buffer and Automatic Recorder Control User s Manual r Digital Audio Corporation A DRI COMPAN Technology to Make Listening Easier SAM II Speech Activity Monitor with Buffer and Automatic Recorder Control User s Manual Document Number 00016AME June 01 2000 r Digital Audio Corporation 5121 Holly Ridge Drive Raleigh NC 27612 Phone 919 782 6767 Fax 919 782 6766 Web www dacaudio com Email sales dacaudio com Copyright 2000 by Digital Audio Corporation All rights reserved TABLE OF CONTENTS 10 OVERVIEW scene reese 1 2 0 THEORY OF OPERATION ccsccssssssssesssssssssessessesassssessesaceneeasesseeaeeasensesneestenees 3 2 1 Voice mamnneraunaannerenneneannanninn 3 2 2 VOICE B fferiN g ententes sine 5 3 0 CONTROL AND CONNECTORS 6 FRONT PANEL S inertie 6 3 2 REAR PANEL Connectors nement 8 4 0 SAM ILOPERATION ns Neutt 10 4 1 SAM Cabling Connections mens 10 4 2 Operational Adjustments mienne 10 4 4 Power 13 5 0 CONFIGURATION ja 14 5 1 Setting Internal DIP Switches nes 14 5 2 Disabling the Aud
7. With the remote cable connected to the SAM Il the recorder should only turn on when the RECORD LED is illuminated on the SAM II front panel Refer to the manufacturer s instructions for remote controlling the specific recorder being used 4 2 5 Maintaining Tape Recorder at Site AUTOmatic Mode The SAM II should require minimum attention while operating in AUTO mode However it will be necessary to periodically check the tape recorder and change the tape if it is nearly full The procedure for changing a tape that is nearly full is as follows 1 Press the START STOP push button on the SAM II front panel to record any remaining captured speech in its buffer on to the tape 2 If the recorder switches ON wait for the RECORD LED on the SAM II front panel to turn OFF 3 Press the STOP and or EJECT button s on the tape recorder remove the recorded tape insert a fresh blank tape and rearm the tape recorder for record operation These tasks should be accomplished within 15 seconds in order to prevent losing any speech which may have accumulated in the SAM II s buffer while changing tapes MANual Mode 12 Periodically check the tape recorder and change the tape if it is nearly full Change the tape quickly to avoid losing speech events 4 4 Power Requirements The SAM is designed to operate from a single 12 VDC power supply The input voltage range is 9 VDC to 18 VDC and the supply must be capable of delivering 500 mA The SAM
8. ccur frequently enough for the overlaps to form a continuous stream of detected speech which is then passed to the control logic Due to the way the bandpass filter is constructed the center frequency can be less than half the bandwidth uong uong qa 0409234 31VH911V9 dOLS LHVLS En 2190 JLVYgIIvo Sd Joyng 1504 94u99 ae Joyng Ew 1 99 SL L AAO NO WV 318Ianv Joyng 91607 20A OLNV ALIAILOV a 5 JoyWedwoy paq al 8 sw Aeleq 5944 L 181114 E A e ul ABieuz ssedpueg Ce Figure 2 SAM II Block Diagram 2 2 Voice Bufferi The buffer control logic selects and isolates the detected voice segments and stores this audio in the 15 second digital FIFO buffer The logic also controls the external tape recorder The BEFORE TIME in the voice detection algorithm requires the audio to be collected in advance of an actual speech detection event This is accomplished by placing an audio delay of seconds to the input audio path The delayed audio is isolated and accumulated in the 15
9. d to a voice detection circuit and a speech FIFO buffer circuit The detection circuit controls the audio collection the SAM Il s 15 second buffer and subsequent audio output to the tape recorder 2 1 Voice Detecti The input audio is initially bandpass filtered to select the spectral segment which gives preference to voice energy This filter is centered at 200 Hz and has a 500 Hz bandwidth The average energy E is then computed for each 32 msec segment of bandpassed audio The algorithm then compares the average energy E with two time varying reference levels These levels are based on the smoothed minimum values of E Each 512 msec the minimum value of E which would be the smallest of the most recent 16 E values is computed This minimum value MIN is then smoothed using a lowpass filter with a long time constant typically 9 seconds The voice detect level Lp consists of SM the smoothed MIN values plus the voice detect threshold THp If E exceeds this voice detect level the algorithm considers this to be a speech event and the SPEECH ACTIVITY LED will be illuminated When a speech event occurs the logic assumes that the voice occurred before and after the detection BEFORE TIME and AFTER TIME values are thus applied to each detection thereby expanding it in time in both directions These BEFORE and AFTER TIMEs are preprogrammed and are specified by the LINE QUALITY control During speech the detections typically o
10. ible Alarm ne 14 5 3 Speech Detection Algorithm Parameters 15 6 0 SAM I SPECIFICATIONS 16 SERVICE ne 18 LIST OF FIGURES Figure 1 SAM Front Panel sscicsscinciscesvsscscssesssscisniedssnncassasaweucisennsusvecuwdscnsieecadvecewassesemnautvansie Figure 2 SAM Block Diagram Figure 3 SAM Rear Figure 4 SAM System Connections Figure 5 SAM II LIST OF TABLES Table 1 Delay anneau ananas 14 Table 2 Speech Detection Parameters nes 15 eech Monitor SPEECH P ACTIVITY 5 del SAM II LINE RECORDER AUDIBLE io O QUALITY CONTROL ALARM QUIET AUTO START ON STOP CALIBRATE Og OFF NOISY MAN OFF 4 DIGITAL AUDIO CORPORATION MADE IN USA 4 Figure 1 SAM Front Panel The SAM Il is an easy to use digital audio VOX and buffer device and is used in conjunction with an audio tape or solid state recorder Unlike conventional VOX switches the SAM Il automatically tracks background noises and detects speech using a thresholded spectral
11. ith a positive center conductor is used 4 0 SAM OPERATION 4 1 SAM Il Cabling Connections Figure 4 illustrates the connection of the SAM II to a monaural portable cassette system using an unbalanced single ended connection and to a professional stereo cassette recorder using a balanced differential connection For mono applications only the cabling for the LEFT channel is required For stereo or two channel applications the LEFT and RIGHT channels are used SAM Il has a built in Automatic Level Control which will automatically apply a gain to the input signal as necessary to achieve adequate level for analog to digital conversion The adjustment of gain is from 0 dB to 20 dB which will allow full scale analog to digital conversion of input signals ranging from 11 dBV to 9 4 2 Operational Adjustments Operating the SAM II consists of four basic steps 1 Selecting LINE QUALITY that is most suitable for site conditions 2 Setting record level of tape recorder 3 Selecting AUTOmatic or MANual mode of RECORDER CONTROL 4 Arming tape recorder for record operation 5 Maintaining tape recorder change tapes etc Instructions for these four steps are outlined in the following sections 4 2 1 Selecting Proper LINE QUALITY Setting Section 3 1 4 discusses adjustment of the LINE QUALITY Switch When in doubt however use the NOISY setting to minimize false alarms 4 2 2 Setting the Record Level of the Tape Recorder
12. l control and power connections are made to the unit s rear panel 3 1 FRONT PANEL Controls 3 1 1 POWER Switch The POWER switch is used to switch ON power to the SAM II When power is ON the POWER LED on the front panel is illuminated 3 1 2 SPEECH ACTIVITY LED The SPEECH ACTIVITY LED lights whenever speech is sensed by the algorithm and is a good indicator of the detection algorithm s performance 3 1 3 RECORD LED The RECORD LED lights when audio is being output to the external tape recorder and the relay is activated 3 1 4 LINE QUALITY Switch The SAM II has two LINE QUALITY settings QUIET and NOISY The user should select the ACTIVITY setting which most closely describes the maximum noise in the environment For example most telephone conversations and most office environments could be recorded using the QUIET position However telephone conversations from cordless or pay telephones in congested areas or noisy office environments with typewriters and printers might require selecting NOISY TIP When in doubt use the NOISY position When the SAM II is left unattended also use the NOISY position 3 1 5 RECORDER CONTROL Switch The SAM Il has two basic modes of operation AUTOmatic and MANual AUTOmatic mode the unit functions as a stand alone speech collection device No input from the operator is required When the unit detects speech in the incoming audio the SPEECH ACTIVITY LED will illuminate and the audio
13. ly weighted algorithm It functions very accurately in both QUIET and NOISY audio environments The SAM has two basic modes of operation AUTOmatic and MANual In MANual mode the instrument provides both visual and audible indication of speech via the high intensity SPEECH ACTIVITY LED and a built in piezo electric buzzer ALARM The ALARM can be disabled by a front panel switch Whenever activity is detected the user can press the START STOP switch to manually activate deactivate the external recorder Thus the MANual mode of operation is designed to assist a human operator which is consistent with normal procedure for law enforcement recording In AUTOmatic mode the instrument stores all detected speech in its internal solid state buffer When the buffer fills or when a built in timeout elapses the external recorder is automatically switched on and the stored speech is recorded onto the tape By buffering the speech in this way tape recorder on off operations are minimized reducing wear on the record mechanism AUTOmatic mode is intended for use in unmanned audio surveillance applications Additional SAM Il features include a CALIBRATE tone which produces a reference record level for the tape recorder and a built in relay which allows the unit to remotely control an external tape recorder by contact closure All audio input and output uses balanced differential signaling which eliminates the possibility of ground loop hum when c
14. oupled to balanced cabling Audio level is adjusted automatically by the microprocessor The SAM II may be connected to both analog and digital recorders Pre detection times are internally adjustable to accommodate record start latencies and DAT backup and overwrite times The SAM Il incorporates LINE QUALITY control for collectively setting the VOX algorithm s optimum pre and post delays guard bands threshold and smoothing time constant for either QUIET or NOISY signals Other panel features include a SPEECH ACTIVITY LED a RECORD LED a RECORDER CONTROL switch a START STOP push button an AUDIBLE ALARM ON OFF switch and a CALIBRATE push button Internal DIP switches allow the technician to specify recorder latency delay Rear panel connectors include balanced stereo inputs and outputs a relay connector for automatic recorder control and a power connector The SAM Il is packaged in a compact rugged aluminum enclosure It is intended for field surveillance applications The unit may be powered from 9 18 VDC or from AC using the supplied AC adapter 2 0 THEORY OF OPERATION The smart VOX algorithm as implemented in the SAM Il is functionally illustrated in Figure 2 The block diagram is shown for a single channel The SAM Il is actually a stereo instrument and two parallel detection and speech buffer channels exist Recorder control is based on speech detection on either or both channels In the figure input audio is passe
15. person Note 2 The asterisk denotes the default positions as they were set at the factory 5 2 Disabling the Audible Al The audible SPEECH ACTIVITY alarm may be turned on and off using the front panel switch however there may be times when the operator may wish to permanently disable the alarm to prevent accidental activation in the field Figure 5 shows the location of Jumper 1 JP1 on the mainboard of the unit Removing the shunt from this jumper disconnects the alarm buzzer from the speech activation circuitry and eliminates the possibility of an accidental sounding of the alarm in the field 14 FRONT OF UNIT Figure 5 SAM Mainboard 53S h Detection Algorithm P i Table 2 contains a listing of the parameters associated with the Quiet and Noisy LINE QUALITY settings Table 2 Speech Detection Parameters LINE Record Record Threshold Center Bandwidth Time QUALITY Before After Time Frequenc Constant Setting Time 200 Hz 500 Hz 200 Hz 500 Hz 15 Analog Line Inputs Two Line Outputs Two Bandwidth Sampling Filters Four Analog Converters Sample Frequencies Control Processor Buffer Delay RAM 6 0 SAM II SPECIFICATIONS 11 to 9 dBV Zn 25 KO minimum Stereo 6 dBV output level Zout 500 Zoaa 600 O 30 to 5500 Hz 0 0025 dB max ripple stopband attenuation gt 85 dB Stereo 24 bit delta sigma analog to digital converter with 128x oversampling and digital decimation fil
16. ration Model SAM Speech Activity Monitor with Buffer and Automatic Recorder Control please contact Digital Audio Corporation 5121 Holly Ridge Drive Raleigh NC 27612 USA Phone 919 782 6767 Fax 919 782 6766 Web www dacaudio com Any comments or suggestions concerning this product would be greatly appreciated 18
17. ters Stereo 24 bit delta sigma digital to analog converter with 128x oversampling and digital interpolation filters DSP 13 0208 kHz A D 39 0625 kHz D A 39 0625 kHz TMS320F206 20 MHz 16 32 bit fixed point DSP 2 megabytes total DRAM 1 second per channel pre trigger delay for detection algorithm 0 1 3 or 7 seconds per channel PRE BUFFER delay to allow for recorder startup 16 Interfaces Enclosure Front Panel Rear Panel Power 15 seconds per channel capture buffer in AUTO mode A D D A panel switches 4 panel push buttons 2 DIP switches 3 panel LEDs 3 recorder control relay 4 1 W x 5 0 D x 1 6 H inches aluminum POWER ON OFF switch POWER SPEECH ACTIVITY and RECORD LEDs Audible speech activity alarm can be disabled ACTIVITY QUIET NOISY switch RECORDER CONTROL AUTO MAN switch START STOP push button AUDIBLE ALARM ON OFF switch CALIBRATE push button which when pressed outputs full scale test tone for adjusting recorder input level Balanced stereo INPUT and OUTPUT Phoenix connectors with removable terminal strip plugs RELAY N O N C and COM Phoenix connector with removable terminal strip plugs Concentric barrel POWER connector center conductor positive 9 18 VDC 250 mA continuous Universal AC adaptor supplied Specifications as of June 1 2000 and subject to change without notice 17 7 0 SERVICE For service or technical questions concerning the Digital Audio Corpo
18. will be buffered into the unit s 15 second solid state memory When this buffer is full when 15 minutes have elapsed or when the START STOP button is pressed the unit switches on the tape recorder and dumps the contents of the buffer onto tape The outgoing speech may be delayed by an adjustable PRE BUFFER amount to allow the tape recorder to bring the tape up to proper record speed before the new recording begins The amount of this PRE BUFFER delay is adjustable by configuring DIP switches 2 and 3 on the main board of the unit See Table 1 Section 5 1 If new speech activity occurs during a buffer dump it will continue to be buffered into the solid state memory so no speech will be lost The MANual mode is a supervised mode in which the operator uses the START STOP button to manually start and stop the recorder When the unit detects speech in the incoming audio the SPEECH ACTIVITY LED will illuminate prompting the operator to press the START STOP button to initiate a new recording In this mode audio could be lost due to slow reaction time from the operator so an AUDIBLE ALARM is provided to quickly get the operator s attention As an additional precaution against the loss speech the audio output of the SAM II can be delayed with respect to the SPEECH ACTIVITY indicators using the PRE BUFFER delay feature The amount of this delay can be adjusted by configuring DIP switches 2 and 3 on the main board of the unit See Table 1 Section
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