OPERATING INSTRUCTIONS E
Contents
1. DEPARTMENT OF TRANSPORT RADIO DIVISION REFERENCE DIAGRAMS AND OPERATING INSTRUCTIONS FOR MARCONI AUTOMATIC ALARM THE MARCONI AUTO ALARM The complete installation consists of receiver type 332 selector type 555 and switch type 272 charging beard tyge 242 and three alarm bells THE RECEIVER type 322 Combined tuner and three valve amplifier The first valve type DER is used as a detector with regeneration The second valve also type DER an audio frequency amplifier and the third a type DEV four electrode valve is used as a relay cir cuit control The aerial is connected through a small condenser to bring all probable ships aerials within range of the tuning limits te an A T I having five taps for coarse adjustment and a var iometer for fine adjustment The aerial condenser is shunted by a resistance to prevent the accumulation of static charges The blocking condenser between earth and filament prevents short cir cuit of the L T battery The coupling between primary and second ary inductances is fixed The closed circuit is permanentiv adjusted to correct wave length but the fixed condenser can be adjusted to small variations if necessary The coupling and damping of the circuit is arranged so that the receiver will be equally sensitive throughout its wave length range 585 to 615 meters The anode of the lst valve is connected through the reaction coil to2. L T primary arm and driving pawl eleotro magnet to negative L T which will energise she magnet and draw pawl wheel around by one tooth The pawl wheel will be held hy the action of a holding pawl If the primary arm closes C contacts a circuit is totipleted from positive L T primary arm Ci contacts to contact QV through re setting magnet to negative of battery This magnet will draw back both driving and holding pawls and allow the pawl wheel to be pulled back to normal starting position by the actien of 5 springs Normally Q centaot is open the contact being closed when pawl wheel commences to rotate otherwise the re setting mag net circuit would be closed through Q and G contacts From the above it will be seen that the pawl wheel will be advanced by one tooth if the signal consists of on unbroken dash of three seconds duration but if it continues for five seconds the shaft of pawl wheel will be returned to starting position Theretore a four second dash will allow the pawl wheel to move by one tooth When D contacts close a circuit is completed through electro magnet of the secondary arm via primary arm D contacts magnet and negative battery This pulls down the secondary arm against the action of a spring When the circuit is open again by D contaets opening the arm commences to rise against the action of a dash pot which retards the motion so that G contacts are not cl
3. Marcc Diagr Approvec Pawl Wheel closes when MT D Magnet pulls down AIK driving pawl when D Contacts close closing I same time Selecron Tyre 333 LT cous Charging Beard Type 242 for information of Examining Officers only DEPT or MARINE Rapio BRANCH Marconi Aufo Alarm Diagram of Connections Approved C IM B L S mew XIL 9
4. the lst and 2nd valves is quite normal With no signal being received a steady current of 7 milliamperes which is equivalent to a reading of 20 on the galvanometer scale flows from filament to inner anode of the 3rd valve through last inter valve transformer and output terminals to relay coils where relay tongue is held against front stop in opposition to the bias of the relay The arrival of an incoming signal makes grid of 8 third valve more negative reducing inner anode filament current and releasing relay tongue if signal is strong enough the tongue will then be pulled back ageinst back stop by bias of relay This sudden reduction in current through last transformer will cause a momentary voltage across the high resistance winding which is so connected as to make the grid still more negative intensifying the action of the incoming signal To prevent the grid of the third valve becoming paralysed there being no grid leak the grid is connected through G terminal to the back stop of main relay so that the grid is discharged when tongue of relay falls over The connection is made to a selected point in the filament circuit so that the grid is restored to its proper value ACTION OF SELECTOR Type 333 The action of the selector is governed primarily py the movement of the tongue of the main relay Normal position is tongue against front stop completing a circuit from positive L T battery through electro magnet of pri
5. also I contact cir cuit and the secondary arm magnet circuit so that the secondary aim is free to commence its upward movement CANADIAN MARCONI COMPANY iontreal Quebec L IT LAMP LT LAMP H T LAMF pO 3 A 5A SA LA UA LT FUSE LTFUSE HT FUSE HT FUSE HT RY o eco O S 0 VOLT POLARITY INDICATOR CHA 4 EDE Pov tk 21112 SWITCH II LT JUTPUT ECEIVER j AND ELECTOR O DISGHARGE HT BATTERY iilis 2113 CHARGE i ejfe NO 2 a LT BATTERIES CHARGING BOARD tvre 242 MARCONI AUTO ALARM VOCATIONAL SCHOOL RADIO DEPARTMENT Switeh Type 272 Pawl Wheel ntact closes when heel moves ju ji DE Magnet pulls down QM driving pawl when D Contacts close closing I at same time LT for information of Examining Officers only Test Terminals Swifeh Type 212 Front Signals cause Stop Back Stop ta leave front stom which epens primary El Dash Pot Secondary Arm pulled down when D Contacts close moves upandclosesGin 5 Seconds when D opens sh Pot arm Contact Hold on Ralay Pawl Wheel contact closes when jrd dash Test Key Normally closed Hold on relay te LT through Z and Frentstop Oconnecti bell
6. and the pawl wheel will return to normal after a total of five seconds dash space and part of the next dash An allowance ef nearly one second is allowed either way in length of space Anything less than two seconds and more than ene fifth of 8 secend Presume three correetly made dashes and spaces to have et received The pawl wheel has been moved three teeth At the terminstion of the last dash the contaet Z will be clesed whieh is in series with the hold on relay Cantacts Z close as soon as the last dash has lasted three secends but ringing cireuit is not completed until the relay tongue has returned to the front stop of completion of the last dash If the last dash lasts five seconds the C contacts will be closed and pawl wheal returned to starting position so that the alarm bells ring only on completion of the last correetly made dash When Z contact eloses due to an alarm signal being re ceived the bell cireuit is completed when relay tongue ef main JA relay returns to the front stop on completion of the last dash The circuit is then through front stop Z contact and Y con tact to alarm bells The hold on relay magnet is then energised closing O contacts which connects the bells directly across the L T battery via Y contacts If the filament current fails or falls toc low the novolt release magnet will allow X to close due to pull of spring und the alarm bell circuit is then complet
7. ed Y opens the hold on relay circuit and bells will cease to ring when the filament current is restored to normal Normally X contacts are open and Y closed ACTION OF H AND I CONTACTS There remains the possibility of false calls by the recep tion of fast Morse or combination of two transmitters being received at once resulting in very short spaces which might cause the prin ary ari to creep up and chatter against 3 contact causing pawl wheel TO move each time giving a false alarm when moved three teeth This is prevented by two additional contacts The H contacts fitted under the primary arm open only when the primary arm is right down and closed as soon as the arm commences its up Ward movenent The I contacts are fitted under the driving pawl and are closed as soon as the driving pawl moves down When the primary arm starts upward the H contacts close D contact is closed in 3 seconds and driving pawl magnet pulls down pawl moving pawl wheel and at the same time closing I con tacts The driving pawl magnet circuit is now completed through I and E contacts whether D contacts are open or closed The I contacts also keep the secondary arm magnet circuit complete The driving pawl and the secondary arm are thus kept down once they have been pulled down and are free to continue their proper action when the primary arm is right down the H contacts are then opened breaking the driving pawl circuit
8. mary arm to negative of battery via relay contects The current through this circuit is normally sufficient to hold the primary arm down against the action of the spring If a signal of sufficient strength is received the tongue will be pulled away from the front stop and the selector can commence to work but if the signal is too weak the relay tongue will fall back to normal position against front stop If a signal of proper strength is received the relay tongue will fall against back stop the grid of the 3rd valve will be discharged the inner anode current will begin to increase again and tongue commence to return to front stop If the signal contin ues the relay current will be reduced again and tongue returns to back stop This continues while amp signal is being received the tengue will chatter against the back stop Meanwhile the selector continues operation because the front stop circuit is open The action of the selector will now be considered first assuming contacts H to be permanently closed and I contacts permanently open 7 When the tongue of the main relay leaves the front stop the circuit through pr ry eleetro magnet is open and the spring commences to pull arm up against the action of the dash pot By adjustments of spring the contacts D will close three seconds after arm commences upward movement and contacts two seconds after D contacts When the D contacts are closed a circuit is gompleted from positive
9. osed until five seconds after the arm commences its upward movenent Suppose a correctly made four second dash is being re ceived the primary arm rises and at the end of three seconds closes D contacts and secondary arm is pulled down alse pawl wheel is moved by one tooth At the end of the four seconds dash primary arm is pulled down again opening D contacts allowing secondary arm te commence its return motion and will ordinarily close G contacts in five seconds Suppose thet after a ene second space another four second dash is started When it has lasted three seconds the D contacts will again be closed and the secendary arm pulled back before contacts G have olesed It has only been allowed four seconds to close G contacts one second of space and three sec onds of the second dash Had the space lasted two seconds er more contacts G would have been closed and as they are in parallel with C contacts the re setting magnet would have been energised and pawl wheel returned to its starting position SUMMARY OF ABOVE A dash ef less than three seconds has no effect on the pawl wheel dash ef three seconds cr over allows the pawl wheel to be advanced by ene teoth amp dash of five seconds will send the pawl wheel back to normal positien A space of two or more seconds will send the pawl wheel back te normal also If the space is too short to allow selector to operate the two dashes will be run into one
10. s direct to LT via Y contacts Pawl Wheel moves Oriving Pawl DE Magnet pulls driving pawl wher contacts close cl at same time Bridge Bell Key Normally closed Test Test Terminals Terminals x C Tyre BIE l D ER DET Ifhem AA Recewer Type 332 Range 585 6 5 4 e acta 278 No Volf L Release 2 No Volt Release Norma X open Bcc Signals c To leave which er arm Co Rimary arm H opens closes H and D then C 2 Secondary Arm pulled down when D Contactsclose reves upand closes G in ELLA Cond Recewer Type 332 Range 585 6 5 4 Bridge Bell Key No Wolt Release Secondary Arm pulled down when D Contacts close moves upand closes ins DR seconds when D opens Tongue Moin Relay 2 68 i BEN biel seen Pawl Wheel A contact closes when Pawl Wheel moves Z closes on 3rd dash Signals cause Tongue ta leave front stop which opens primary arm Contact ini DR Magnet pulls down UI driving pawl when D contacts close closing I atsame time Hold on relay te LT through Z and Front stop Oconnect bells direct LT via Y contacts Sevector Trre 333 cells For in Officer DEPT Rapio
11. the medium resistance winding of the lsts inter valve transformer The low resistance winding to telephone ter minals is used for testing purposes only The high resistance winding is connected between grid and filament o the 2nd valve in the usual manner The anode of the 2nd valve is choke capacity coupled to grid of 3rd valve A low resistance winding on this choke is also used for testing with telephones The inner anode of the rd valve is connected through a large var ieble resistance to the medium resistance winding of the last transformer thence through a shunted galvanometer to Noe 2 output terminal which is connected to coils of main relay in selector returning via Nos 1 terminal to H T positive The outer anode of the 3rd valve is connected through the high resistance winding to its own grid l The filaments of all valves are connected in series through a fixed and a variable resistance and a no volt relay te the lt 4 volt L T supply The resistances are on the positive side the negative side being earthed The total anode voltage is 56 volts made up of 24 velt L T and 12 volt H T supply a total of 36 volts above the negative point Should the filament current through any valve drop below normal or cease the no volt relay will operate and ring the alarm bells The valves require 2 volts on each filament The DER type filament current 55 amperes the DE 4 amperes ACTION OF RECEIVER The actien of
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