Press Button loop disconnect telephone, with provision for four additional press buttons.

It was produced from a Telephone No. 710 but modified as follows:-

  • A push button Signalling Unit replaces the dial.
  • The dial aperture in the cover is enlarged to cater for the keyset.
  • A Box Connection and Cord, Instrument No. 20/03AJ Grey 72" are supplied with the telephone and sender.

Used with Sender No. 6A (shown to the right) which is mains powered.  The digits pressed on the telephone are stored in the Sender before being converted to Loop Disconnect signals and sent to line.  A maximum of 16 digits can be stored.

The interdigital pause can be adjusted on the Sender No. 6.

The Telephone No. 730F was used at BP Trading Ltd.

Circuit Diagrams - N830 (Telephone) and SA4222 (Sender).

GPO Press & Broadcast Notice

6th December, 1965


Press-button telephones are to be put on trial for three months among nearly 300 subscribers on the Langham telephone exchange in London early next year.

The press-button telephone has ten buttons instead of the ten finger holes in the dial of the ordinary telephone. On the experimental telephones being used for the trial the buttons are arranged in two rows of five:-

1 2 3 4 5
6 7 8 9 0

but future standard instruments are likely to have them in the form:-

1 2 3
4 5 6
7 8 9

Two different experimental systems will be put on trial at Langham exchange. One uses voice frequency tone signalling generators inside the telephone working into special equipment in the exchange.

In the other system the press-button telephone is connected to operated convertor, which can be placed under the table or and does not need any special equipment at the exchange.  This can be used therefore, for internal calls on existing types of private exchange, as well as to other numbers on the public network.

Press-button telephones enable the user to complete his "dialling" action much more quickly - as quickly in fact as he can press the buttons. This not only saves some time, but will enable all-figure numbers to be keyed with less chance of error. The time saving in setting up the call will be greatly increased on the fast switching electronic exchanges of the future. Press-button telephones being put on a further trial at the new electronic exchange opening at Leighton Buzzard next year will enable calls to other Leighton Buzzard numbers to be completed as fast as the buttons can be pressed.

Technical data from the trials will assist in the design of standard press-button telephone systems that may be offered as an optional facility in the future and assessment of their popularity will help in working out possible costs and charges.

In the field of data transmission press-button techniques offer the possibility of developing new methods of feeding simple data into a computer over telephone lines.

If all goes well there may be a big opportunity for exporting press- button telephones. The Post Office has, therefore, a double interest in the success of the trials. First to pioneer a system that will help subscribers, and second to boost British exports of an advanced technological kind.

Additional information

Tele 730FMk 1y 4/64Dictation control fitted
Tele 1/730FMk 1y 4/64As 730F but with bell loudness control
Tele 730LMk 1y 4/64 
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Last revised: April 30, 2023