See also Autodial No. 301

User Guide

3 Internal
Issue 2, JAN 1977

Description and Installation

This Instruction describes the Autodial No. 302A (Card 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 is a "repertory dialler" with a punched card memory and is used in conjunction with the normal telephone. Each telephone number is punched on an individual card, which has a capacity of 16 digits. About thirty cards can be stored in the recessed top of the autodial. The autodial is mains-powered with an integral power unit, measures 5.5in x 6in x 4in and weighs 3.5 lb. When the mains supply is switched on, the red opal on the lid of the autodial glows.

When a punched card is placed in the slot, the autodial pulses the first recorded digit. The card then drops, under the force of gravity, until arrested by a latch. The next digit is then transmitted. This procedure continues until all the recorded digits have been transmitted, when the card drops from the slot and is caught by a transparent tray fitted to the base.

When a punched card is positioned in the slot, light shines through the punched out holes in the card on to photocells. The difference in the resistance of the lit and unlit photocells sets a pulse counter and starts a pulse generator.
The pulse generator sends dial pulses to line and steps the pulse counter until it is restored to zero, at which time the generator stops and a monostable multivibrator is set to give an interdigital pause (IDP ) of 850 ms. The latch on which the card is resting is released and the second latch is operated to allow the card to drop to the position in which the next row of holes is presented to the photocells.

After this number has been pulsed out, the second latch is released and the first re-operated, to allow the following row of holes to be presented to the photocells. This process is repeated until no holes are presented to the photo cells causing both latches to be released and allowing the card to fall-from the slot. If an exchange line access digit at a PABX is required to precede the telephone number, the digit is recorded in the normal manner but one additional hole is punched. When this particular hole is presented to the appropriate photocell the IDP is extended to allow main exchange dial tone to be obtained prior to the dialling of the remaining digits. Should an incorrect card be inserted in the slot, the call may be cancelled at any time during the dialling process by pressing the button in front of the card slot, and replacing the telephone handset.

The cards (Card, Autodial, D 92879) are supplied in boxes of 50. Each card is 2in x 3in, has five columns of 16 semi-punched holes and, on the edges, 42 two columns of slots in which the latch pins locate. A roughened surface is provided at the top, on which to write the name or other details of the relevant subscriber, and down the left-hand side, on which to write the number being called. Each row of holes corresponds to one digit of the telephone number starting from the bottom and working upwards.
This code is derived by deducting the required digit from 16 and punching out the holes required to total the result. The first column on the left represents the value 1, the second column the value 2, the third column the value 4, and the fourth column the value 8, e.g. to record the digit 7, 16-7 = 9, 9 is represented by punching out the hole in the 1 column and the hole in the 8 column, the digit 0 must be considered as 10, i.e. 16-10 = 6 represented by holes in the 2 and 4 column. The use of the fifth column of holes is explained in par 4.

When more than 700 cards are required kit Autodial 3/D 93151, item Code 372724 should be supplied.

A guide is provided to facilitate the recording of telephone numbers on the cards as follows:-

(a) Write the name of the subscriber to be called at the top of the card, and the number to be recorded along the left hand side, starting from the bottom with each digit coinciding with one row of holes.

(b) Using the guide, line up the first digit to be recorded with the corresponding digit on the guide and punch through the holes provided.

(c) Slide the card in the guide to locate the second digit to be recorded with the corresponding digit on the guide and repeat as in (b).

(d) Repeat (c) for third and subsequent digits.

(e) After the last digit has been recorded slide the card from the guide. It is now ready for use in the autodial.

When a guide has not been provided, the cards should be prepared in the manner described above.

The autodial automatically inserts an interdigital pause of about 850 ms. The card can be programmed to provide a long IDP. A special column of semi-punched holes (the fifth) is provided for this facility. After punching out the digit preceding the long pause, the hole in the fifth column in the same row is punched out. The hole corresponding to this facility is designated * on the guide.

The long IDP is 2.5 to 3 seconds on the Autodial No. 302A.

(a) Select the bard with the desired name and number on it.

(b) Lift the telephone handset and obtain dial tone.

(c) Insert the card in the slot, with the subscribers name at the top, and allow it to fall freely into the slot.

The autodial will now automatically transmit the recorded number leaving the call held by the telephone.

To call a number not recorded on a card the telephone dial is used in the normal manner.

(a) Connect a three-pin plug to the mains lead, to suit the socket outlet provided by the subscriber. If a fused plug is used the fuse rating should not be more than 3 amp. A three-pin plug must be used and the green/yellow wire must be connected to the earth terminal.

(b) Locate the autodial near the telephone. It may be connected in all automatic exchange areas to any ordinary telephone installation, PBX operator's dialling circuit or any extension which is provided with a dial. The autodial should be connected to the exchange line or extension pair whenever practicable by using the existing terminal block.

When the autodial is connected to a 700 type telephone or to a switchboard dialling circuit the spark quench strap must be removed. This strap consists of a wire link connected between two pillars and is located on the rear printed circuit board.

On completion of the installation it should be ensured that the subscriber can operate the autodial, has a copy of the operating instructions and understands that the telephone dial can be used in the normal manner when a telephone number is required which has not been recorded on a card, or if the autodial fails to function, e.g. during a mains failure.

(c) Apparatus to be Requisitioned

Autodial No. 302A Item Code 372712
Kit Autodial 1/D 93151 (Punch and Guide Kit) Item Code 372644
Kit Autodial 2/D 93151 (Box of 50 Cards) Item Code 372645
Kit Autodial 3/D 93151 (Box of 1000 Cards) Item Code 372724


The lid is removed by slackening the two screws at the rear of the base and one screw underneath the card slot projection. Two further screws, passing through the transparent tray, secure the case to the chassis. The removal of these will allow the chassis to be withdrawn. Before removing the chassis from the case the mains supply must be disconnected.

An extract from


There are two versions of the Autodial No. 302A. Mk I or Mk II.

For identification the Autodial has printed on its base the manufacturers code, the year of manufacture and the suffix ... /I or ... /II to denote the mark number.

Dial Ratio Link on Mk II Autodials
The dial ratio is a preset adjustment by means of a two-position link. To change the dial ratio remove the lid. The dial ratio link is next to the LKA strap. It will be noticed that the link is soldered to a post at one end and at the other has a socket which is pushed onto one of two other posts. Should the socket be on the 66-33 post it should be carefully removed from that post and pushed onto the 60-40 post.

On no account may any other control on the Mark II Autodial be adjusted.

Adjustment to Autodial
Before adjusting the Autodial it is necessary to determine whether the version to be adjusted is a Mark I or Mark II version.

Mark I Version
Adjustment can be made by rotating potentiometer RV2 which is located on the left hand printed circuit board of the Autodial. Access can be gained to the potentiometer be removing the lid as described in paragraph 4.

Rotation of RV2 clockwise increases the dial ratio.

Rotation of RV2 anticlockwise decreases the dial ratio. Dial pulse speed can be adjusted by rotation of RV1. On no account may any control on the Mark II Autodial be adjusted.
If the Autodial fails to function correctly after all tests and adjustments have been made it must be replaced.

Replace the Dial Test Card in the box for future use by the customer or maintenance staff.

Introduced in 1971.

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

Repertory Diallers

The Autodial No. 30lA stores its dialling information on plastic cards, each card being programmed for one telephone number by having holes punched out in accordance with a simple code. Any telephone number consisting of up to 16 digits can be recorded in this way.

This autodial is a self-contained unit with an internal mains-driven power unit, measures approximately 6 in x 4 in x 6 in and weighs 34 lb. In the top of the unit is a card chute through which the card falls during automatic dialling. The card is arrested at each row of punched out holes by a solenoid latch pin, until on completion of dialling the card drops out into a translucent tray. A storage compartment for thirty cards is provided behind the card chute. A call may be cancelled at any time during the dialling process by pressing the button which is situated in front of the card slot, and replacing the telephone handset.

The cards, which measure 3.5 in x 2.25 in, are moulded in A.B.S. Copolymer with 16 rows of potential holes, each hole covered with a thin web which can be removed as required with a suitable pointed instrument. Writing surfaces are provided along the top and down the left-hand side for the name and telephone number, respectively, of the called subscriber.

A typical card is shown to the right, each row of holes corresponds to one digit of the telephone number. The code is derived by deducting the number required from 16, and punching out holes corresponding to the result, where the first column on the left represents the value 1, the second column the value 2, the third column the value 4 and the fourth column the value 8. Therefore, for the digit 7, code digit 9 must be recorded, i.e. holes punched out in column 1 and column 8. The digit 0 must be considered as 10, hence holes to the value 6 would be punched out. A jig is provided to assist the user in programming cards correctly.

The line circuit of the autodial consists only of the pulsing contact, a mercury-wetted reed with a standard spark quench, and two mask contacts performing a similar function to the dial off-normal contacts. Dry-reed inserts are utilized for the mask-relay functions.

The autodial is normally connected between the incoming exchange-line pair and the telephone instrument, the pulsing contacts being inserted in the B-leg of the line, and one set of the mask contacts being connected across the line. On multiple telephone installations it is necessary to connect the autodial into one of the telephone instruments in series/ parallel with the telephone dial. Both mask contacts are required for this type of connexion, but the autodial spark quench must be disconnected.

A simplified block schematic of the Autodial 30lA circuit is shown below. To make a call the user lifts the telephone handset, obtains dial tone and inserts a selected card in the chute. The card comes to rest against a latch pin, with the bottom row of holes aligned between the light source and the photo-conductive cells which detect the digit value. The presence of the card operates the card-detect circuit, which in turn operates the mask relay, to short-circuit the line in preparation for pulsing, and triggers the i.d.p. generator. The latter enables the pulsing control circuitry to be used for the control of the first digit in the same manner as for subsequent digits, but without operating the latch control.

The dial-pulse generator is clamped by the output from the i.d.p. generator. The termination of this output triggers a 5 ms timer which provides a setting potential for the

When the 5 ms timer restores, the dial-pulse generator, a free running multivibrator, starts sending impulses to line and stepping the pulse counter. When the counter reaches its home state (binary it triggers the i.d.p. generator which clamps the dial-pulse generator, and causes the latch to release for 35 ms. This allows the card to fall and be caught by the latch pin locating in the first feed hole in the card. In this position the second row of holes is aligned between the photo-conductive cells and the light source. This process continues until no punched holes are presented to the photoconductive cells. The number-sent detector then operates, releasing the latch until the card has fallen from the chute, and releasing the mask relay to enable conversation to take place.

If a public-exchange access digit from a p.a.b.x. is required to precede a national or an international telephone number, the access digit is recorded in the normal manner using the first row of holes, but the fifth hole is also punched out. The detection of this fifth hole causes the following i.d.p. to be increased to two seconds. This allows time for public exchange dial tone to be connected before the remainder of the telephone number is transmitted.


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Last revised: November 26, 2010