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Concept
Push-button telephone
Summary
The push-button telephone is a telephone that has buttons or keys for dialing a telephone number, in contrast to having a rotary dial as in earlier telephone instruments.
Western Electric experimented as early as 1941 with methods of using mechanically activated reeds to produce two tones for each of the ten digits and by the late 1940s such technology was field-tested in a No. 5 Crossbar switching system in Pennsylvania.Bell Telephone Laboratories, A History of Engineering and Science in the Bell System – Switching Technologies (1975, AT&T) The technology at that time proved unreliable and it was not until after the invention of the transistor that push-button technology became practical. On 18 November 1963, after approximately three years of customer testing, the Bell System in the United States officially introduced dual-tone multi-frequency (DTMF) technology under its registered trademark Touch-Tone. Over the next few decades touch-tone service replaced traditional pulse dialing technology and it eventually became a world-wide standard for telecommunication signaling.
Although DTMF was the driving technology implemented in push-button telephones, some telephone manufacturers used push-button keypads to generate pulse dial signaling. Before the introduction of touch-tone telephone sets, the Bell System sometimes used the term push-button telephone to refer to key system telephones, which were rotary dial telephones that also had a set of push-buttons to select one of multiple telephone circuits, or to activate other features. Digital push-button telephones were introduced with the adoption of metal–oxide–semiconductor (MOS) integrated circuit (IC) technology in the early 1970s, with features such as the storage of phone numbers (like in a telephone directory) on MOS memory chips for speed dialing.
The concept of push buttons in telephony originated around 1887 with a device called the micro-telephone push-button, but it was not an automatic dialing system as understood later.
Official source
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