AUTODIAL No. 301


See Autodial No. 302

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

Repertory Diallers
T. G. SIMMONDS, B.SC., and P. A. BURTON

CARD CALLMAKER
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.

Connexion
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.

Operation
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 0.0.0.0.) 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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