GPO Telephones - Type 756 Push Button

Type 756 Push Button

Similar to the 746, but fitted with push buttons instead of a dial.

Just as the 700 type came about as a result of public demand. fuelled by US television shows, so the advent of 'Touchtone Dialling' in later American TV output brought about a demand for the same at home in the UK. Unfortunately the GPO did not yet have the exchange equipment necessary to support 'Touchtone' or DTMF (Dual Tone Multi-Frequency) as the GPO preferred to call it. So they decided to introduce a simulated version instead. This would comprise a very ordinary 700 type instrument, with a push button mod. kit fitted. Beneath the smart-looking buttons, a small converter circuit, powered by re-chargeable Ni-Cd cells, would convert the button presses back to perfectly normal, 10 impulse per second, loop-disconnect dial output, i.e. the new keypad was made to simulate an old rotary dial.

But this was the GPO, and nothing was ever that simple. Even though all the design research had already been done by the major US companies, The GPO decided to do it all over again. Although, initially, they decided to modify the existing 700-type instruments, what hadn't been decided was how the push-buttons should best be laid out. Completely ignoring the then-standard US layout, an experiment was put into motion at the Dollis Hill Research Centre. Mock-ups were made of every conceivable combination and layout of buttons. Each of these had its own seated operator and digital readout. All the button pads and readouts were cabled to a primitive computer. For weeks on end the computer flashed random series of numbers to the digital readouts and the operators had the task of punching these numbers, as quickly as possible, onto the keypads. The speed and accuracy rate were continuously logged, as was the ergonomic comfort of the operators. At the end of many months, much expense, and to absolutely no-one's surprise, the results came out in favour of the existing American layout! Sadly this was too late for at least one major company. ICI had decided to press ahead unilaterally with their own design, the Tele 726, which had two rows of five buttons (no # or * buttons then) set horizontally across the centre of a circular face-plate. This proved very awkward to use.

This was the outcome of the trials. A perfectly normal Tele. 746, but fitted with push buttons instead of a dial and re-dubbed 756. The push buttons just created the same loop disconnect signalling pulses as a dial telephone, which caused horrendous post-dialling delay and much knuckle rapping frustration.

The model shown in the photograph is actually an 8756, which has been modified to enable it to be used with the 'New Plan' plug and socket system.

• 8756 Two Tone Grey Telephone

• 8756 Base, showing that this telephone was refurbished in 1982 and that this was a telephone rented from BT