AUTODIAL No. 401
Autodial No. 401, sales name Single Number Callmaker, was made by GEC and field trailed in late 1976/early
The Callmaker was eventually marketed late 1979 as the Mono Callmaker.
On marketed models the lid could be padlocked to a hasp. Earlier models could be
retrofitted using a Lock Bar No 2.
Early models were titled Single Number Callmaker.
GEC developed and produced this Autodial.
AUTODIAL No. 401A (Mono Callmaker)
It has the facilities for storing and sending a single telephone number of up to eleven digits including PABX access digits. Digit storage is set up by slide controls which operate a switch matrix. The autodial can be used with a normal or loudspeaking telephone and in all cases a press switch will be needed to activate the autodial. The switch is normally fitted in the telephone.
When connected to a PABX extension the access digit(s) is stored before the main exchange number. To allow for correct seizure of the exchange equipment, facilities are provided (by the use of pause slide controls) to increase the inter-digit pause that follows the pulsing of the access digit(s). The interdigital pause is normally 2 seconds, but by changing an internal strap it can be increased to 5 seconds.
To make a call using the autodial, to a number which has been previously programmed with the slide controls, the telephone handset is lifted, and when dial tone is received the call switch is operated, the programmed number is then automatically sent at 10 pps.
If the autodial is used on a PABX extension the PAUSE slide control(s) inserts an interdigital pause of 2 seconds. If due to congestion or circuit design, the receipt of dial tone from the main exchange is delayed a strap in the dialler can be moved which will increase the interdigit pause to 5 seconds.
FIELD OF USE
The autodial will not operate with any apparatus using multi-frequency or direct current signalling e.g. MF or DC Keyphones.
The autodial has been designed for wall mounting, made possible by three holes in the baseplate and is connected to a block terminal by a 4-wire cable (Diagram N2315 refers). The autodial should be fixed at a height which will. allow easy access for programming. Only in exceptional circumstances should the auto-dial be fixed in a horizontal position or provided as a free standing item. Connection to the block terminal in these circumstances should be made using a 4 way cord (CORD INST 4/121AT) where possible.
Access to Terminals and Fixing Holes
The method of connection is shown in Diagram N2315.
Long Interdigit Pause
On later models a bracket is supplied with the autodial and when the case is removed the bracket will be found temporarily fixed by tape to the top right hand corner of the autodial. This bracket is fitted under the single screw that fixes the case to the baseplate. The knockout in the lid will then have to be removed so that when the lid is closed the bracket protrudes through the lid and a padlock can then be inserted through the hold in the bracket.
For test purposes it is also necessary to check that all slide controls function correctly. Ideally a single test number that fills all slide control positions should be programmed and checked, but as such a number is unlikely to be available then a series of test numbers will have to be programmed and checked for correct access. The autodial needs to find a number in the FIRST slide control position but it will release if it does not find a number programmed in any of the next 6 slide control position (on in any consecutive 6 positions). The test numbers must be programmed to fill position 1 and other positions with no more than 5 blanks between digits. The following example shows how these requirements can be met using a single "FICTITIOUS" 4 digit test number 2121.
On completion of testing re-enter the customer's required number.
Testing On PABX Installations
A long interdigit pause, following the access digit(s), can be obtained if required, by moving a strap as detailed above.
An extract from the memoir's of ex GEC employee Martin Pickering
My very first design project at GEC Aycliffe was the "Single Number Callmaker" or "Autodial No. 401A". The original Autodial was a large box full of cams, cogs and contacts. When you heaved down on the plunger it set a flywheel in motion that drove the various cams and cogs to open and close the contacts at 10 pulses per second. It could be "programmed" to dial out a complete telephone number of up to (I think) ten digits.
My job was to design the base and plastic cover mouldings to meet the Post Office specifications. One problem was that it needed a hinged lid for access to the slide switch matrix but the Post Office boys did not want any visible hinges. It took me six months to develop an ingenious plastic spring hinge made of acetal copolymer ("delrin") to do the job. I imagine the total development cost was astronomical and I think we eventually manufactured just a few thousand. By that time, push-button "MF" (tone) dialling phones were on the drawing board and the Autodial was obsolete.
This electronic replacement "Autodialler" derived all of its power from the telephone line. The required digits were set by means of a slide switch matrix designed by the "Mechanical Department" (Godfrey Hall) under John Leworthy. The electronic circuit design was by, as I recall, "Sparky Bob" Stevenson and Maurice Weeks in the Electronics Design department run by "Sam" Crooks. A custom I.C. was designed to control the operation of the two mercury-wetted relays whose job it was to "loop the line" and provide the pulses. The I.C. was horrendously expensive to develop and produce. A ferrite transformer oscillator was employed to take the small current from the telephone line and convert it to a stable voltage supply.
Last revised: April 01, 2022