Push-button telephone
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A push-button telephone is a
telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...
that has buttons or keys for dialing a telephone number, in contrast to a
rotary dial A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone numb ...
used in earlier telephones.
Western Electric Western Electric Co., Inc. was an American electrical engineering and manufacturing company that operated from 1869 to 1996. A subsidiary of the AT&T Corporation for most of its lifespan, Western Electric was the primary manufacturer, supplier, ...
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.Push. Click. Touch. – History of the Button – 1963: Pushbutton Telephone
– December 11, 2006
The technology at that time proved unreliable and it was not until after the invention of the
transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...
that push-button technology became practical. The Bell System selected
Findlay, Ohio Findlay ( ) is a city in Hancock County, Ohio, United States, and its county seat. The second-largest city in Northwest Ohio, Findlay lies about 40 miles (64 km) south of Toledo, Ohio, Toledo. Its population was 40,313 at the 2020 United Sta ...
as the first city in the U.S. for marketing tests of touch-tone service and Ohio Bell began installing push-button telephones in Findlay homes starting on 1 November 1960. The next market was in Greensburg, Pennsylvania">"Phone Without Dial Makes Bow in Ohio", by Jim Flanagan, ''Cleveland Plain Dealer'', February 27, 1961, p.1 ("The Ohio Bell Telephone Co. began installations Nov. 1.") The next market was in Greensburg, Pennsylvania
, starting on 1 February 1961. On 18 November 1963, after approximately three years of customer feedback, the
Bell System The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the AT&T Corporation, American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America fo ...
officially introduced dual-tone multi-frequency (DTMF) technology in Carnegie, Pennsylvania and increased its use in Greensburg, under its registered trademark ''Touch-Tone''. Over the next few decades touch-tone service replaced traditional
pulse dialing Pulse dialing is a signaling technology in telecommunications in which a direct current local loop circuit is interrupted according to a defined coding system for each signal transmitted, usually a digit. This lends the method the often used ...
technology and it eventually became a world-wide standard for telecommunication signaling. Although DTMF signaling was the driving technology implemented in push-button telephones, some telephone manufacturers used push-button
keypad A keypad is a block or pad of buttons set with an arrangement of digits, symbols, or alphabetical letters. Pads mostly containing numbers and used with computers are numeric keypads. Keypads are found on devices which require mainly numeric in ...
s to generate
pulse dial Pulse dialing is a signaling technology in telecommunications in which a direct current local loop circuit is interrupted according to a defined coding system for each signal transmitted, usually a digit. This lends the method the often used ...
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 upright=1.3, Two power MOSFETs in amperes">A in the ''on'' state, dissipating up to about 100 watt">W and controlling a load of over 2000 W. A matchstick is pictured for scale. In electronics, the metal–oxide–semiconductor field- ...
(MOS)
integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
(IC) technology in the early 1970s, with features such as the storage of phone numbers (like in a
telephone directory A telephone directory, commonly called a telephone book, telephone address book, phonebook, or the white and yellow pages, is a listing of telephone subscribers in a geographical area or subscribers to services provided by the organization tha ...
) on
MOS memory Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a sili ...
chips for
speed dialing Speed dial was a function available on many telephone systems allowing the user to place a call by pressing a reduced number of keys. This function was particularly useful for phone users who dial certain numbers on a regular basis. In most cas ...
.


History

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. This use even predated the invention of the
rotary dial A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone numb ...
by
Almon Brown Strowger Almon Brown Strowger (; February 11, 1839 – May 26, 1902) was an American inventor for whom the Strowger switch, an electromechanical telephone exchange technology, is named. Early years Strowger was born in Penfield, New York, near Roches ...
in 1891.The New York Times – "When Dials Were Round and Clicks Were Plentiful"
- by Catherine Greenman, October 1999
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 Direct distance dialing (DDD) is a telecommunications service in North America by which a caller may call any other subscriber outside the local calling area without operator assistance, DDD was introduced in the United States in 1951, on a tri ...
required automatic transmission of dialed numbers between distant exchanges, leading to the use of inband
multi-frequency signaling In telephony, multi-frequency signaling (MF) is a type of signaling that was introduced by the Bell System after World War II. It uses a combination of audible tones for address (telephone number) transport and supervision signaling on trunk li ...
within the Long Lines network while individual local subscribers continued to dial using standard pulses. As direct distance dialing 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 A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, rea ...
was eleven digits, including the leading 1. In the 1950s,
AT&T AT&T Inc., an abbreviation for its predecessor's former name, the American Telephone and Telegraph Company, is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the w ...
conducted extensive studies of product engineering and efficiency and concluded that push-button dialing was preferable to rotary dialing. Initial customer trials for the push-button telephone were conducted by the end of the 1950s in Hamdon, Connecticut, in a step-by-step switching system, and in Elgin, Illinois, in a No. 5 Crossbar central office. In 1960, approximately one fourth of the central office in Findlay, Ohio, was equipped with touch-tone digit registers for the first commercial deployment of push-button dialing, starting on 1 November 1960. In 1962, Touch-Tone telephones, including other Bell innovations such as portable pagers, were on display for the public to try out at the Bell Systems pavilion at the Seattle World's Fair. 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 dialing was commercially offered by Bell Telephone to customers in the
Pittsburgh Pittsburgh ( ) is a city in Allegheny County, Pennsylvania, United States, and its county seat. It is the List of municipalities in Pennsylvania#Municipalities, second-most populous city in Pennsylvania (after Philadelphia) and the List of Un ...
area towns of Carnegie and Greensburg,
Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...
,Engineering Pathway – Bell Telephone introduces push button telephone
– by Alice Agogino – November 18, 2009
after the DTMF system had been tested for several years in multiple locations, including Greensburg. This phone, the
Western Electric Western Electric Co., Inc. was an American electrical engineering and manufacturing company that operated from 1869 to 1996. A subsidiary of the AT&T Corporation for most of its lifespan, Western Electric was the primary manufacturer, supplier, ...
1500, had only ten buttons. In 1968 it was replaced by the twelve-button model 2500, adding the asterisk or star (*) and the octothorpe or 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 signaling Dual-tone multi-frequency (DTMF) signaling is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and Automatic telephone exchange, switching center ...
. Although push-button touch-tone telephones made their debut to the general 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 The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the AT&T Corporation, American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America fo ...
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 additional equipment at the
telephone exchange A telephone exchange, telephone switch, or central office is a central component of a telecommunications system in the public switched telephone network (PSTN) or in large enterprises. It facilitates the establishment of communication circuits ...
to decode the tones. However, most telephone exchanges in the early 1970s only supported pulse dialling based on the
Strowger switch The Strowger switch is the first commercially successful electromechanical stepping switch telephone exchange system. It was developed by the Strowger Automatic Telephone Exchange Company founded in 1891 by Almon Brown Strowger. Based on its ...
system, restricting touch-tone telephones to some
private branch exchange A business telephone system is a telephone system typically used in business environments, encompassing the range of technology from the key telephone system (KTS) to the private branch exchange (PBX). A business telephone system differs from ...
s (PBX). Tone to pulse converters were later added to linefinder groups in Step by Step offices to allow some subscribers to use DTMF sets. British companies Pye TMC, Marconi-Elliott and GEC developed a new
digital Digital usually refers to something using discrete digits, often binary digits. Businesses *Digital bank, a form of financial institution *Digital Equipment Corporation (DEC) or Digital, a computer company *Digital Research (DR or DRI), a software ...
push-button telephone technology, based on
metal–oxide–semiconductor upright=1.3, Two power MOSFETs in amperes">A in the ''on'' state, dissipating up to about 100 watt">W and controlling a load of over 2000 W. A matchstick is pictured for scale. In electronics, the metal–oxide–semiconductor field- ...
(MOS)
integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
(IC) chip technology. It was variously called the "MOS telephone", the "push-button telephone chip", and the "telephone on a chip". It used
MOS integrated circuit upright=1.4, gate oxide">insulating layer (pink). The MOSFET (metal–oxide–semiconductor field-effect transistor) is a type of insulated-gate field-effect transistor (IGFET) that is fabricated by the controlled oxidation of a semiconduct ...
(MOS IC) logic, with thousands of MOS transistors on a chip, to convert the keypad input into a pulse signal. This made it possible for push-button telephones to be used with pulse dialling at most telephone exchanges. MOS telephone technology introduced a new feature to push-button telephones: the use of
MOS memory Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a sili ...
chips to store phone numbers, which could then be used for
speed dialing Speed dial was a function available on many telephone systems allowing the user to place a call by pressing a reduced number of keys. This function was particularly useful for phone users who dial certain numbers on a regular basis. In most cas ...
at the push of a button. This was demonstrated in the United Kingdom by Pye TMC, Marconi-Elliot and GEC in 1970. Between 1971 and 1973,
Bell Laboratories Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several lab ...
in the United States combined MOS technology with touch-tone technology to develop a push-button MOS touch-tone phone called the "Touch-O-Matic" telephone, which could store up to 32 phone numbers in an electronic
telephone directory A telephone directory, commonly called a telephone book, telephone address book, phonebook, or the white and yellow pages, is a listing of telephone subscribers in a geographical area or subscribers to services provided by the organization tha ...
stored on
memory chip Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a sil ...
s. This was made possible by the low cost, low power requirements, small size and high reliability of MOS transistors, over 15,000 of which were contained on ten IC chips, including one chip for logic functions (such as
shift registers A shift register is a type of digital circuit using a cascade of flip-flops where the output of one flip-flop is connected to the input of the next. They share a single clock signal, which causes the data stored in the system to shift from one loca ...
and counters), one for the keypad dial interface, and eight for memory storage. By 1979, touch-tone phones were gaining popularity, but it was not until the 1980s that the majority of customers owned push-button telephones in their homes; by the 1990s, it was the overwhelming majority. Some exchanges no longer support pulse-dialing or charge their few remaining pulse-dial users the higher tone-dial monthly rate as rotary telephones become increasingly rare. Dial telephones are not compatible with some modern telephone features, including
interactive voice response Interactive voice response (IVR) is a technology that allows telephone users to interact with a computer-operated telephone system through the use of voice and DTMF tones input with a keypad. In telephony, IVR allows customers to interact with a ...
systems, though enthusiasts may adapt pulse-dialing telephones using a pulse-to-tone converter. Most, but not all VoIP analogue Telephone Adapters (ATA) will only support DTMF dialling.


Touch-tone

The international standard for digit signaling by telephones specifies dual-tone multi-frequency (DTMF) signaling, more commonly known as touch-tone dialing. It replaced older and slower
pulse dial Pulse dialing is a signaling technology in telecommunications in which a direct current local loop circuit is interrupted according to a defined coding system for each signal transmitted, usually a digit. This lends the method the often used ...
systems. The push-button format is also used for all
cell phones A mobile phone or cell phone is a portable telephone that allows users to make and receive Telephone call, calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones (landline phone ...
, but with
out-of-band signaling In telecommunications, signaling is the use of signals for controlling communications. This may constitute an information exchange concerning the establishment and control of a telecommunication circuit and the management of the network. Classi ...
of the dialed number. The touch-tone system uses audible dual tones for each of the digits. Later this was expanded by two keys labeled with a star (*) and a symbol called the square, similar to the pound or hash sign (#), to represent the 11th and 12th DTMF signals. These signals accommodate various additional services and customer-controlled calling features. The DTMF standard assigns specific frequencies to each column and row of push-buttons of the telephone keypad; the columns in the push-button pad use a set of higher-frequency tones than the rows, both in the audible range. When a button is pressed, the dial generates a combination signal of the two frequencies from the high and low groups, respectively, producing a dual-tone signal, which is transmitted over the telephone line to the central office. When introduced, the DTMF technology was not immediately available on all switching systems. The circuits of subscribers requesting the feature often had to be moved from older switches that supported only pulse dialing to a newer crossbar, or later an electronic switching system, requiring the assignment of a new telephone number which was billed at a higher monthly rate. Community dial office subscribers would often find the service initially unavailable as these villages were served by a single unattended exchange, often step by step, with service from a
foreign exchange The foreign exchange market (forex, FX, or currency market) is a global decentralized or over-the-counter (OTC) market for the trading of currencies. This market determines foreign exchange rates for every currency. By trading volume, it i ...
impractically expensive. Rural party line service was typically based on mechanical switching equipment which could not be upgraded. While a tone-to-pulse converter could be deployed to any existing mechanical office line using 1970s technology, its speed would be limited to pulse dialing rates. The new central office switches were backward-compatible with rotary dialing.


DTMF keypad layout

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-dialing 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 dialing. The remaining digits occupied the lower rows in sequence from left to right; the 0, however, was placed into the center of the fourth row, while omitting the lower left and lower right positions. The DTMF keyboard layout broke with the tradition established in cash registers (and later adopted in calculators and computers) of having the lower numbers at the bottom. This was due to research conducted by Bell Labs using test subjects unfamiliar with keypads. Comparing various layouts including two-row, two-column, and circular configurations, the study concluded that while there was little difference in speed or accuracy between any of the layouts, the now familiar arrangement with 1 at the top was the most favourably rated.R. L. Deninger
Human Factors Engineering Studies of the Design and Use of Pushbutton Telephone Sets
, The Bell System Technical Journal, vol. 39, no. 4, July 1960
The engineers had envisioned telephones being used to access computers, and surveyed business customers for possible uses. This led to the addition of the
number sign The symbol is known as the number sign, hash, (or in North America) the pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a Typographic ligature, ligatured abbre ...
(#, ''pound'' or ''diamond'' in this context, ''hash'', ''square'' or ''gate'' in the UK, and '' octothorpe'' by the original engineers) and
asterisk The asterisk ( ), from Late Latin , from Ancient Greek , , "little star", is a Typography, typographical symbol. It is so called because it resembles a conventional image of a star (heraldry), heraldic star. Computer scientists and Mathematici ...
or ''star'' (*) keys in 1969. Later, the hash and asterisk keys were used in vertical service codes, such as ''*67'' to suppress
caller ID Caller identification (Caller ID) is a telephone service, available in analog and digital telephone systems, including voice over IP (VoIP), that transmits a caller's telephone number to the called party's telephone equipment when the call is ...
in the Bell System. In military telephone systems four additional signals (A, B, C, D) were defined for signaling call priority.


Pulse dialing

Historically, not all push-button telephones used DTMF dialing technology. Some manufacturers implemented
pulse dialing Pulse dialing is a signaling technology in telecommunications in which a direct current local loop circuit is interrupted according to a defined coding system for each signal transmitted, usually a digit. This lends the method the often used ...
with push-button keypads and even
Western Electric Western Electric Co., Inc. was an American electrical engineering and manufacturing company that operated from 1869 to 1996. A subsidiary of the AT&T Corporation for most of its lifespan, Western Electric was the primary manufacturer, supplier, ...
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. Pulse-mode push-button keypads typically stored the dialed number sequence in a digit collector register to permit rapid dialing for the user. Some push button pulse dial phones allow for double-speed pulse dialing. These allow even faster pulse dialing in exchanges that recognize double-speed pulse dialing. As telephone companies continued to levy surcharges for touch-tone service long after any technical justification ceased to exist, a push-button telephone with pulse dialing capability represented a means for a user to obtain the convenience of push-button dialing without incurring the touch-tone surcharge.


DC signaling

Heemaf 1955 type wall telephone by Philips with DC signaling pushbutton dial (Netherlands, Dec.1962). In the 1950s, the Dutch electronics concern
Philips Koninklijke Philips N.V. (), simply branded Philips, is a Dutch multinational health technology company that was founded in Eindhoven in 1891. Since 1997, its world headquarters have been situated in Amsterdam, though the Benelux headquarter ...
developed a direct current (DC) signaling method for dialing 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 dialed digit between the two line conductors and ground return, which were analyzed in the exchange by relay logic.B.H. Geels, N. Scheffer, ''Keyset Selection of Telephone Numbers'', Philips Telecommunication Review, Volume 17(1), August 1956, p.30–37 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).


Features

Electronics within push-button telephones may provide several usability features, such as last number redial and storage of commonly called numbers. Some telephone models support additional features, such as retrieval of information and data or code and PIN entry. Most
analog telephone adapter An analog telephone adapter (ATA) or FXS gateway is a device for connecting traditional analog telephones, fax machines, and similar customer-premises devices to a digital telephone system or a voice over IP telephone network. An ATA is often ...
s for
Internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
-based telecommunications (
VoIP Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...
) recognize and translate DTMF tones but ignore dial pulses, an issue which also exists for some PBX systems. Like cellular handsets, telephones designed for voice-over-IP use out-of-band signaling to send the dialed number.


See also

*
History of the telephone This history of the telephone chronicles the development of the electrical telephone, and includes a brief overview of its predecessors. The first telephone patent was granted to Alexander Graham Bell in 1876. Mechanical acoustic devices ...
*
Mobile phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This rad ...
*
Timeline of the telephone This timeline of the telephone covers landline, radio, and cellular telephony technologies and provides many important dates in the history of the telephone. 1667 to 1875 * 1667: Robert Hooke creates an acoustic string telephone ...
*


References

{{DEFAULTSORT:Push-Button Telephone Telecommunications-related introductions in 1963 Telephony equipment