The History of the Touch-Tone Telephone Keypad

This week in 1963, touch-tone phones were used for the first time, as an alternative to the traditional rotary dial. The people of Carnegie and Greensburg, in Pennsylvania USA, were the guinea pigs for the then revolutionary technology.

The 1-2-3 telephone keypad that we are all so familiar with today was the invention of an industrial psychologist named John E Karlin. Whilst working at Bell Laboratories, Karlin convinced his bosses that human testing could help to improve the design of the telephone. Early mechanical calculators were designed with the smallest numbers closest to the user in a 7-8-9 arrangement, a concept which has been attributed to inventor David Sundstrand and his 10-key keypad. This is a system that is still used today on all computer keyboards and calculators. However, Karlin was not convinced that this would be the best arrangement for the telephone and so he began to test alternative designs on the employees where he worked.

In total, sixteen variations were trialled. This included the 10-key keypad arrangement used on calculators as well as fewer rows with more numbers, column arrangements and a variety of circular designs that were similar to the traditional rotary dial. In the end, the 7-8-9 arrangement used on calculators didn’t even come close to the winning 1-2-3 keypad arrangement.

Touch-tone phones use technology called dual-tone multi-frequency (DTMF) dialling, which sends tone sequences from phones to the central office of the local phone company. In comparison, the previous rotary dial phones generated a series of pulses, or clicks, by rapidly and repeatedly connecting and disconnecting a caller’s phone line. The equipment at the central office exchange would then count the number of clicks generated by this repeated motion in order to determine the number being called. This meant that those wishing to make long distance calls either required operator assistance or the provision of subscriber trunk dialling equipment.

After around three years of human testing, the Bell System officially introduced the touch-tone phone in the USA on November 18th 1963. The next few decades that passed saw the touch-tone phone replacing traditional rotary design, pulse dialling technology. Eventually, push-button technology became the global standard for telecommunications signalling.

Bell Laboratories reportedly contacted many of the larger calculator manufacturers, attempting to share their research findings. However, their response was not as expected, as it transpired that none of these companies had ever actually done any user testing. Needless to say, the conventional arrangement on the calculator remains the same today, whilst the 1-2-3 touchtone keypad arrangement is now used on door locks, vending machines, medical equipment and ATMs, amongst other things.