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Push-button telephone


The push-button telephone is a telephone that uses buttons or keys for dialing a telephone number to place a call to another telephone subscriber.

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. But the technology proved unreliable and it was not until long after the invention of the transistor when push-button technology matured. 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 Touch-Tone mark. 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.

The concept of the use 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. This use even predated the invention of the rotary dial by Almon Brown Strowger in 1891. The Bell System in the United States relied on manual switched service until 1919, when it reversed its decisions and embraced dialed, automatic switching. The 1951 introduction of direct distance dialing required automatic transmission of dialed numbers between distant exchanges, leading to use of inband multi-frequency signaling within the Long Lines network while individual local subscribers continued to dial using standard pulses.


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