The push-button telephone is a telephone that has buttons or keys for dialling 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. 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 trademark Touch-Tone.
Over the next few decades, touch-tone service replaced traditional pulse dialling technology, and it eventually became a world-wide standard for telecommunication signalling.
Although DTMF was the driving technology implemented in push-button telephones, some telephone manufacturers used push-button keypads to generate pulse dial signalling. 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 dialling.
More information: Telekom
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 dialling 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 dialled automatic switching.
The 1951 introduction of direct distance dialling required automatic transmission of dialled numbers between distant exchanges, leading to the use of inband multi-frequency signalling within the Long Lines network while individual local subscribers continued to dial using standard pulses.
As direct distance dialling expanded to a growing number of communities, local numbers (often four, five, or six digits) were extended to standardized seven-digit named exchanges. A toll call to another area code was eleven digits, including the leading 1.
In the 1950s, AT&T conducted extensive studies of product engineering and efficiency and concluded that push-button dialling was preferable to rotary dialling.
After initial customer trials in Connecticut and Illinois, approximately one fourth of the central office in Findlay, Ohio, was equipped in 1960 with touch-tone digit registers for the first commercial deployment of push-button dialling, starting on 1 November 1960.
On 22 April 1963 President John F. Kennedy started the countdown for the opening of the 1964 World's Fair by keying 1964 on a touch-tone telephone in the Oval Office, starting a contraption which will count off the seconds until the opening.
On November 18, 1963, the first electronic push-button system with touch-tone dialling was commercially offered by Bell Telephone to customers in the Pittsburgh area towns of Carnegie and Greensburg, Pennsylvania, after the DTMF system had been tested for several years in multiple locations, including Greensburg. This phone, the Western Electric 1500, had only ten buttons.
In 1968, it was replaced by the twelve-button model 2500, adding the asterisk or star (*) and pound or hash (#) keys. The use of tones instead of dial pulses relied heavily on technology already developed for the long line network, although the 1963 touch-tone deployment adopted a different frequency set for its dual-tone multi-frequency signalling.
Although push-button touch-tone telephones made their debut to the public in 1963, the rotary dial telephone still was common for many years. Sales of touch-tone telephones picked up speed during the 1970s, though the majority of telephone subscribers still had rotary phones, which in the Bell System of that era were leased from telephone companies instead of being owned outright.
Adoption of the push-button phone was steady, but it took a long time for them to appear in some areas. At first, it was primarily businesses that adopted push-button phones.
The touch-tone system required the need for additional equipment at the telephone exchange to decode the tones. However, most telephone exchanges in the early 1970s only supported pulse dialling based on the Strowger switch system, restricting touch-tone telephones to some private branch exchanges (PBX).
More information: University of Salford
The international standard for telephone signalling utilizes dual-tone multi-frequency (DTMF) signalling, more commonly known as touch-tone dialling. It replaced the older and slower pulse dial system. The push-button format is also used for all cell phones, but with out-of-band signalling of the dialled number.
The standard layout of the keys on the touch-tone telephone was the result of research of the human-engineering department at Bell Laboratories in the 1950s under the leadership of South African-born psychologist John Elias Karlin (1918–2013), who was previously a leading proponent in the introduction of all-number-dialling in the Bell System. This research resulted in the design of the DTMF keypad that arranged the push-buttons into 12 positions in a 3-by-4 position rectangular array, and placed the 1, 2, and 3 keys in the top row for most accurate dialling.
The remaining digits occupied the lower rows in sequence from left to right; the 0, however, was placed into the centre of the fourth row, while omitting the lower left and lower right positions.
Historically, not all push-button telephones used DTMF dialling technology. Some manufacturers implemented pulse dialling with push-button keypads, and even Western Electric produced several telephone models with a push-button keypad that could also emit traditional dial pulses. Sometimes the mode was user-selectable with a switch on the telephone.
In the 1950s, the Dutch electronics concern Philips developed a direct current (DC) signalling method for dialling telephone numbers, for use in the UB-49 private branch exchange (PBX) system. The push-button dial pad used an arrangement of semiconductor diodes to produce a distinct sequence of polarity states for each dialled digit between the two line conductors and ground return, which were analysed in the exchange by relay logic.
In 1968, the system was used in the UK, in a brief excursion from standards, when the General Post Office (GPO) introduced the first UK-made push-button telephone, the GPO 726 (Ericsson N2000 series).
More information: EDN
that lessen the barriers of time and distance
-the telegraph and cable, the telephone, radio, and the rest.
Emily Greene Balch
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