Issue 2, MAR 1972

Description and installation of Autodial No. 201A

This Instruction describes the Autodial No. 201A (Tape Callmaker), which enables subscribers connected to automatic exchanges to call other frequently used subscribers numbers without the necessity of remembering or dialling the telephone numbers. To call other subscribers the normal telephone dial may be used. The Autodial No. 201A with its associated power unit and dial unit is shown in the picture.

The autodial is a 'repertory dialler' with a magnetic tape store on which a maximum of 400 telephone numbers may be stored. Each telephone number can have up to a maximum of sixteen digits. To record the numbers the dial unit is plugged into the rear of the autodial. A lamp is provided on the autodial which has two purposes; in the recording process it is used as a WAIT lamp and in the play back mode it is used as a DIALLER IN USE indicator. In earlier models this lamp was part of the dial unit and could only be used during the recording process. The unit can insert a minimumintertrain pause of 600ms.

The Autodial No. 201A comprises the following units:-

(a) Desk unit. A black coloured unit measuring approximately 10in by 5in by 3in containing the electronic circuits and a 12ft 3in. wide, magnetic tape roll. The unit is supplied with 5ft of five way cable to connect it to the power unit and 3ft of six way cable to connect it to the telephone.

(b) Power unit. A grey coloured unit measuring approximately 5in by 3.5in by 3in containing the mains step-down transformer, rectifiers and d.c. smoothing components. The unit is supplied with 2 metres of mains cable.

(c) Dial unit. A unit consisting of a modified dial mounted on a wooden base.

In addition to the above units it will be necessary to provide a three-pin plug to suit the mains socket outlet provided by the subscriber.

(a) Location of units

Desk unit. The desk unit should be located in a convenient position near the telephone instrument or, where the autodial is associated with a switchboard dialling circuit, in a convenient position for the switchboard operator.

Power unit. The power unit should be located close to a mains socket outlet and mounted such that the cable entry holes are at the bottom. Four round-head woodscrews No. 6 should be used to secure the unit to the wall.

Dial unit (shown to the right). The dial unit is only used during the recording of telephone numbers and when not in use should be stored by the subscriber in a convenient cupboard or drawer.

(b) Connection

The desk unit should using the five-way cable supplied with the desk appropriate. If necessary, the length of cable terminating it on a suitable terminal block and to the power unit with Cable, P.V.C. No 5A, to be connected to the power unit unit and may be extended up to 30 ft by then connecting the terminal block Wire 20. Care should be taken to avoid incorrect connection as this could seriously damage the autodial.

(i) Connection to a telephone instrument. The six way cable supplied with the desk unit should enter a 700 type telephone instrument via the knock-out in the rim of the base normally used for the watch receiver cord. To avoid damage to the sheath of the cable, care should be taken to remove any sharp edges from the rim of the hole, especially on those telephone instruments with metal bases. On pre 700 type telephone instruments, the cable should enter the telephone via the normal cord entry hole. For some installations it may be necessary to use spare telephone terminals or an auxiliary connection strip within the instrument. To avoid strain on the cable conductors the six-way cable should be secured inside the telephone in a convenient manner.

(ii) Connection to a switchboard dialling circuit The six way cable supplied with the desk unit should enter the switchboard in any suitable manner and be connected into the switchboard dialling circuit. The six way cable may be extended, if necessary, by the use of Cable, PVC, No. 5A, 6 Wire 20. The overall length of the cable should not exceed 30 ft. and the two cables should be joined by the use of a suitable terminal block. To avoid strain on the cable conductors a cable strainer should be provided at the termination of the six-way cable supplied with the desk unit. It should be noted that where the switchboard dialling circuit is provided in an operator's telephone, i.e. as on some 2/... switchboards, the desk unit should be connected to that telephone as described in (i).
The Autodial No. 201A must not be connected directly to an exchange line pair as the pulsing contacts are not quenched and also, due to circuit arrangements, the line would be seized during a recording sequence.

When the Autodial No. 201A has been installed it should be ensured that:-
(a) An outgoing call from the telephone or switchboard can still be made in the ordinary way when the mains supply to the autodial is connected or disconnected.

(b) An incoming call can still be received satisfactorily on the telephone to which the autodial is connected.

(c) A telephone number can be successfully recorded and transmitted with the autodial.

(d) The subscriber is able to operate the autodial satisfactorily.

(a) Recording a telephone number Ensure the mains supply is connected to the autodial and with the Telephone handset at rest proceed as follows:-

(i) Raise the metal cover at the front of the desk unit and move the index tape so that the desired position on the tape is resting on the red platform. The index tape may be moved quickly by pressing the TAPE DRIVE key situated on the right-hand side of the desk unit. The final positioning of the index tape is achieved by pressing and rotating the SELECTOR wheel.

It should be noted that the approximate position of the index tape is indicated by a red line which scans the letters of the alphabet engraved on the front cover and printed on the window of the desk unit.

(ii) Write, in pencil, on the unshaded portion of the index tape between two black lines the name and/or telephone number to be recorded.

(iii) Close the metal cover and, using the SELECTOR wheel, move the index tape so that the writing appears between the two black lines on the window of the unit. The operation of the CALL button will move the index tape, if necessary, so that the writing space is located centrally between the two black lines on the window. The lines on the window will not necessarily coincide with those on, the index tape.

(iv) Connect the dial unit to the desk unit with the plug provided. The socket is on the rear of the desk unit.

(v) Depress and release the CALL button.

(vi) Dial the required number on the dial unit ensuring that the WAIT lamp darkens before dialling each digit.

(vii) When all the digits of the telephone number have been dialled, depress and release the STAR button.

(viii) Disconnect the dial unit from the desk unit.

NOTE:- When the autodial is connected to the extension of a PABX and an external call is to be recorded it is necessary to insert a 'stop' condition after the public exchange access digit. The procedure to be followed is as detailed in (i) - (viii) except that after the public exchange access digit has been dialled the STAR button should be depressed and released before dialling the remaining digits. The STAR button must still be depressed and released at the end of dialling.

(b) Making a call to a recorded number Ensure the mains supply is connected to the autodial and proceed as follows:-

(i) Using the index tape positioning controls locate the wanted number between the two black lines on the desk unit window.

(ii) Lift the telephone receiver or, for a switchboard, seize the exchange line and listen for dial tone.

(iii) Depress and release the CALL button.

NOTE:- When the autodial is connected to the extension of a PABX and an external call is to be made operation of the CALL button will cause the transmission of the access digit only. When the public exchange dial tone is received the STAR button must be operated to cause the remainder of the digits to be transmitted.

The transmission circuit will be short-circuited during dialling and will be reconnected when dialling ceases.

(c) Changing, a recorded number, Proceed as detailed in (a) erasing the original writing from the index tape with a soft rubber eraser. Recording the new number automatically erases the old number from the magnetic tape.

Introduced in 1970


Maintenance is limited to changing complete units except for cords, lamps, fuses and tape.

The Autodial 210A consists of 3 items:-
Dial Unit - SA5203
Power Unit - SA5203
Translator - SA5203
Which are in themselves one Rate Book item.

To inspect the desk unit remove the screws from each corner of the base and take off the cover, the cords can then be checked and changed if necessary. The Lamp (which is a push fit) can also be checked and changed.

Lamps and cords can now be obtained if required from PO Factories division. (See T1 E5 F3212 Issue 3).

The Recording head can be observed by either removing the cover as above, or by removing the cassette cartridge (press cassette release roller as shown in the picture below).

When the call button is pressed the tape head will move across the tape from left to right for about 3.5 secs. This action will take place on blank tape or even if the cassette is removed, regardless of whether the handset is on or not. If digits are recorded then it will move across the tape pulsing each digit in turn.

If these actions do not take place the complete Deck unit should be changed.

When changing the desk unit the original cassette should be retained, if fault free, so that it can be used in the new callmaker. The new callmaker should then be thoroughly tested to ensure that wrong numbers are not sent out to line due to possible misalignment of the tape head on the new machine. Only when test calls show that the original will not function in the new machine should a blank cassette be left with the customer thus necessitating re-recording. In any event a cassette either, old or new, should be returned to the stores in the exchanged desk unit.


To replace the tape (Tape recording 4A).

Remove Cassette from Unit by pressing the release roller.

Remove the four Cassette base screws. Wind the tape fully to the 'Z' end and detach the tape from the 'A' end by lifting the masking tape - the A end will rapidly unwind. Now remove the tape from the Z spool.

Take the 'A' end of the new tape and fix this to the A spool with masking tape, now wind the tape onto the spool in the direction shown by the arrow. When all the tape is wound on the other end should then be threaded around the toothed drive wheel rollers towards the Z end.

The Z spool should then be tensioned by winding it about 40 times in the opposite direction to that shown below, whilst tensioning the Z spool the A spool should be held to prevent the wound on tape from slipping.

The Z end of the tape is then fixed with masking tape. The base is then refitted and the Cassette can be replaced in the desk unit. A test number should be dialled in, and then pulsed out to ensure correct operation.

The dial itself is a special item and cannot be interchanged with a normal telephone dial and complete units only should be changed.

If wrong number faults are reported and the speed/ratio are suspected:-

  1. Drive tape to blank space and then dial onto the tape a series of 0's.

  2. On the next space on the tape dial in the digits 1 - 0.

The speed and ratio can then be checked with the R.S.C. also the correct of every digit.  When the R.S.C. has been contacted move tape to position and press call button for speed/ratio and to position (b) and press call check of digits.

Maintenance consists of checking voltages and fuses.


Additional Pictures

Front View
The aluminium coloured metal flap at the front of the case allowed the user to write on the roll with a pencil
Base View
The view shows the base plate and magnetic roll mechanism removed
The magnetic tape could break.
Spare rolls of magnetic tape were available
and maintenance engineers would replace them.

Customers on the other hand would
create like made as they had to programme
in the numbers!
Base of Autodial showing the manufacturers label  


Extract from an article on Repertory diallers in the POEEJ, Vol 62, page 188, October 1969.

Repertory Diallers

The Autodial No. 201A is manufactured in the USA by the DASA Corporation under the trade name of Magicall. The Plessey Co., Ltd., market the device in the United Kingdom, but have carried out some modifications to enable Post Office requirements to be met.

The complete device is made up of three units, the desk unit, the power-supply unit and the recording-dial unit. The magnetic-tape store has a capacity of 400 telephone numbers each of which can have a maximum of 18 digits.

The magnetic tape is cassette loaded with one side prepared as a writing surface and divided along its length into alphabetical sections. A red line runs diagonally from the A-end to the Z-end to assist in alphabetical location when the fast-wind facility is used. The final position of the tape is adjusted by the selector wheel.

The power-supply unit provides four voltages: -20volts d.c. for the pulsing circuit, -10 volts d.c. for the amplifier and timing circuits, +20volts d.c. for the Schmitt-trigger bias and 28 volts a.c. for the scan and tape-head motors. These supplies and an earth are connected to the main unit by a five-way cord.

The recording-dial unit consists of a modified Dial Automatic No. 21 LA in a Mounting Dial Automatic No. 22A. This is connected to the desk unit by a nine-way cord, plug and

This is connected to the desk unit by a nine-way plug and socket. The dial has been modified to include a motor start contact in series with the off-normal contact. This extra contact breaks when the dial is taken off normal, and makes while the dial is restoring. The tape head is thus driven across the tape by the tape-head motor only during pulsing.

The autodial is connected to a telephone installation by a six-way cord. The line circuit consists of a dry-reed pulsing contact and two make contacts. The autodial must be connected to the installation such that the existing spark quench can be used. The connexion arrangement must also ensure that the pulsing contacts are isolated from the line during the recording of new numbers.

To record a telephone number, the recording-dial unit is plugged into the socket provided at the rear of the desk unit. The flap on the front of the autodial is lifted and the name or number is written in pencil on the chosen position on the tape. The tape is then moved to locate the entry between the black lines on the window. The CALL button is depressed and the lamp on the recording-dial unit glows. When the lamp darkens the first digit of the telephone number can be dialled. As soon as the dial starts to restore the lamp glows again. It will remain glowing for a period after the dial has returned to normal, when it darkens again the next digit can be dialled. The period between the dial restoring to normal and the lamp darkening corresponds to a pre-determined inter-digital pause. Using this procedure the entire telephone number can be recorded. After the last digit has been recorded the STAR button is pressed which causes the lamp to glow again. This provides a sufficient length of blank tape after the final digit to ensure correct switch off when playing back. When it darkens again the recording is complete and the recording-dial unit can be disconnected.

Should an access digit from a p.a.b.x. installation be required to precede the national or international number, then the STAR button is pressed after the access digit has been dialled, again to provide an extra-long pause. When the lamp darkens the remainder of the number can be recorded as previously described.

While a recording is being made the telephone handset must be left on the rest to prevent the number being transmitted to line.
To call a number which has been recorded, the appropriate position on the tape is selected and the telephone handset lifted. When dial tone is obtained, the CALL button is pressed, this causes the number to be automatically transmitted to line, and after pulsing leaves the call held by the telephone loop. If an access digit has been transmitted, the dialler will stop. When main-exchange dial tone is obtained the STAR button is pressed and the remainder of the number is automatically sent to line.

Outline Circuit Operation
The diagram above shows a simplified block schematic of the operation of the Autodial 20lA. The tape is moved to the selected number, and when the CALL button is pressed, the head-motor control switches to the ON state and the tape head is driven across the tape in search of a pulse. When the head detects a pulse the Schmitt trigger switches and restores, and by restoring sets the auxiliary bistable and the pulsing bistable to the ON state. The auxiliary bistable prepares the circuit for the i.d.p., and the pulsing bistable releases the pulsing relay sending a break to line. The pulse-correction circuit in the break-pulse timer resets the pulsing bistable to the OFF state after 61 ms, re-operating the pulsing relay and hence making the pulsing contacts. The head continues travelling across the tape and when another pulse is detected the Schmitt trigger switches and restores, causing the same sequence of operations to be repeated. After the final pulse of the digit a period of one second can elapse before the motor-control timer restores, but if a further series of pulses are detected within this time pulses from the Schmitt trigger maintain the auxiliary bistable in the ON state and set the pulsing bistable successively into the ON state.
If an access digit has been recorded the motor will stop one second after the access digit has been sent. The remainder of the number is sent by depressing the STAR button as soon as the second dial tone is heard.

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