Push-button telephone

Short description: Telephone which has buttons or keys for dialing

The Western Electric No. 2500, a typical American 12-button phone of the 1970s and early 80s

Gigaset A165 push-button cordless telephone using DECT with a base station

A push-button telephone is a telephone that has buttons or keys for dialing a telephone number, in contrast to a rotary dial used in earlier telephones.

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.[1][2] The technology at that time proved unreliable and it was not until after the invention of the transistor that push-button technology became practical.

The Bell System selected Findlay, Ohio 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.[3] The next market was in Greensburg, Pennsylvania, starting on 1 February 1961.[4]

On 18 November 1963, after approximately three years of customer feedback, the Bell System officially introduced dual-tone multi-frequency (DTMF) technology in Carnegie, Pennsylvania and increased its use in Greensburg, under its registered trademark Touch-Tone.[5] 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 signaling 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.

## Contents

* 1 History
* 2 Touch-tone
* 2.1 DTMF keypad layout
* 3 Pulse dialing
* 4 DC signaling
* 5 Features
* 6 See also
* 7 References

## 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 by Almon Brown Strowger in 1891.[6] 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 the use of inband multi-frequency signaling 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 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 dialing was preferable to rotary dialing.[7]

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.[8] 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.[9][10]

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".[11] 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 area towns of Carnegie and Greensburg, Pennsylvania,[7][12] 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 the octothorpe or pound or hash (#) keys.[13] 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. 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,[14] 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.[15] Adoption of the push-button phone was steady, but it took a long time for them to appear in some areas.[16] At first it was primarily businesses that adopted push-button phones.[17]

The touch-tone system required 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). 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 push-button telephone technology, based on metal–oxide–semiconductor (MOS) integrated circuit (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 (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.[18][19]

MOS telephone technology introduced a new feature to push-button telephones: the use of MOS memory chips to store phone numbers, which could then be used for speed dialing at the push of a button.[18][19][20] This was demonstrated in the United Kingdom by Pye TMC, Marconi-Elliot and GEC in 1970.[18][19] Between 1971 and 1973, Bell Laboratories 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 stored on memory chips. 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 and counters), one for the keypad dial interface, and eight for memory storage.[21] By 1979, touch-tone phones were gaining popularity,[22] 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 [16] or charge their few remaining pulse-dial users the higher tone-dial monthly rate[23] as rotary telephones become increasingly rare.[24][25][26] Dial telephones are not compatible with some modern telephone features, including interactive voice response 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 systems.[27][28] The push-button format is also used for all cell phones,[22] but with out-of-band signaling 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.[7][29]

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.[7]

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.[30][31]

### DTMF keypad layout

DTMF keypad layout |

DTMF dialing

File:DTMF dialing.ogg

How DTMF dialing sounds

|

* * *

Problems playing this file? See media help.

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.[32] 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.[33] 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.[34]

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 (#, pound or diamond in this context, hash, square or gate in the UK, and octothorpe by the original engineers) and asterisk or star (*) keys in 1969. Later, the hash and asterisk keys were used in vertical service codes, such as *67 to suppress caller ID in the Bell System.{{citation needed|date=November 2020}

## Pulse dialing

Iskra ETA85 pushbutton telephone with pulse-dialing keypad (Yugoslavia, 1988).

## 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 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.[35]

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).[36][37]

British GPO 726 telephone with DC signaling dial pad (1968).

## Features

Telia Mox and Fido

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.[38]

## See also

* History of the telephone
* Mobile phone
* Timeline of the telephone

## References

1. ↑ Bell Telephone Laboratories, A History of Engineering and Science in the Bell System – Switching Technologies (1975, AT&T)
2. ↑ Push. Click. Touch. – History of the Button – 1963: Pushbutton Telephone – December 11, 2006
3. ↑ [https://www.newspapers.com/article/the-plain-dealer-the-testing-of-the-push/160770253/ "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.")
4. ↑ "Greensburg to Be Test Model for Telephone", AP story in The Gettysburg (PA) Times, February 2, 1961, p.8
5. ↑ "2 Pa. Towns First To Get 'Touch' Phones", UPI report in The Evening Sentinel (Carlisle PA), November 15, 1963, p.4
6. ↑ The New York Times – "When Dials Were Round and Clicks Were Plentiful" \- by Catherine Greenman, October 1999
7. ↑ 7.0 7.1 7.2 7.3 "telephone | History, Definition, & Uses". https://www.britannica.com/technology/telephone.
8. ↑ Experimental Set Using Push Buttons Placed on Trial, Bell Laboratories Record, August 1959, p. 313
9. ↑ AT&T, J.G. Lindsay (ed.), December 1960, Touch-Tone Phones Offered, Long Lines, Vol. 40 (5), 25.
10. ↑ "Findlay's Bicentennial - Visit Findlay". http://visitfindlay.com/about/findlays-bicentennial/.
11. ↑ "President Starts Countdown for Fair", Associated Press report in The Gettysburg Times, April 23, 1963, p11
12. ↑ Agogino, Alice (November 18, 2009). "Engineering Education "Today in History" Blog: Bell Telephone introduces push button telephone". http://www.k-grayengineeringeducation.com/blog/index.php/2009/11/18/engineering-education-today-in-history-blog-bell-telephone-introduces-push-button-telephone-2/.
13. ↑ "Milestones in AT&T History – 1963". https://www.corp.att.com/history/milestone_1963.html.
14. ↑ "/ccpa/". https://archive.triblive.com/ccpa/?page=/news/allegheny/4291278-74/phone-touch-tone.
15. ↑ "When We Dialed Telephone Numbers". http://www.irememberjfk.com/mt/when_we_dialed_telephone_numbe.php.
16. ↑ 16.0 16.1 "I Remember JFK – Push-Button Telephones". http://www.irememberjfk.com/mt/pushbutton_telephones.php.
17. ↑ "What is a Touch-Tone Telephone? (with pictures)". http://www.wisegeek.com/what-is-a-touch-tone-telephone.htm.
18. ↑ 18.0 18.1 18.2 "Push-button telephone chips". Wireless World: 383. August 1970. https://www.americanradiohistory.com/hd2/IDX-Site-Early-Radio/Archive-Wireless-World-IDX/70s/Wireless-World-1970-08-OCR-Page-0023.pdf.
19. ↑ 19.0 19.1 19.2 Valéry, Nicholas (11 April 1974). "Debut for the telephone on a chip". New Scientist (Reed Business Information) 62 (893): 65–7. ISSN 0262-4079. https://books.google.com/books?id=u0O-g0_fbrIC&pg=PA65.
20. ↑ Electronic Components. U.S. Government Printing Office. 1974. p. 23. https://books.google.com/books?id=HikuAAAAMAAJ&pg=PA23.
21. ↑ Gust, Victor; Huizinga, Donald; Paas, Terrance (January 1976). "Call anywhere at the touch of a button". Bell Laboratories Record 54: 3–8. http://doc.telephonecollectors.info/dm/76Jan_BLR_P3_Touch_A_Matic.pdf#page=2.
22. ↑ 22.0 22.1 "What is a Touch Tone Telephone? (with pictures)". http://www.wisegeek.com/what-is-a-touch-tone-telephone.htm.
23. ↑ "SaskTel ending rotary dial service". CBC News – Saskatchewan. 2012-04-02. https://www.cbc.ca/news/canada/saskatchewan/sasktel-ending-rotary-dial-service-1.1254117.
24. ↑ TimesDaily.com – Advances make many items close to obsolete – by Tom Smith & Bernie Delinski – October 14, 2009 – Retrieved February 10, 2010
25. ↑ The Free Lance-Star – Aug 12, 1994, by Michael Zitz, page 1 – Rotary phone users in info highway's slow lane
26. ↑ Sacramento Business Journal – Rotary phones ring true for few – all but gone from workplace – March 9, 2001
27. ↑ "General Telephones — History". http://www.cntr.salford.ac.uk/comms/pushbutton.php.html.
28. ↑ "What is a Rotary Phone? (with pictures)". http://www.wisegeek.com/what-is-a-rotary-phone.htm.
29. ↑ "Telephone Timeline – Greatest Engineering Achievements of the Twentieth Century". http://www.greatachievements.org/?id=3625.
30. ↑ Mitel Application note MSAN-108: Applications of the MT8870 integrated DTMF receiver, Page A50, Figure 2 (MT8870 DTMF receiver, MT4325 Pulse dialer), June 1983. A tone-to-pulse converter was one of Mitel's first products in 1973.
31. ↑ United States Patent 3959598: Identification forwarding circuit for use with tone-to-pulse converters, filed April 15, 1974.
32. ↑ Fox, Margalit (February 8, 2013). "John E. Karlin, Who Led the Way to All-Digit Dialing, Dies at 94". The New York Times. https://www.nytimes.com/2013/02/09/business/john-e-karlin-who-led-the-way-to-all-digit-dialing-dies-at-94.html.
33. ↑ Staff, Straight Dope (July 16, 2002). "Why do telephone keypads count from the top down, while calculators count from the bottom up?". https://www.straightdope.com/21343156/why-do-telephone-keypads-count-from-the-top-down-while-calculators-count-from-the-bottom-up.
34. ↑ 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
35. ↑ B.H. Geels, N. Scheffer, Keyset Selection of Telephone Numbers, Philips Telecommunication Review, Volume 17(1), August 1956, p.30–37
36. ↑ "TELE No. 726". https://www.britishtelephones.com/t726.htm.
37. ↑ "Telephone No.726". http://www.samhallas.co.uk/repository/n_diagrams/0000/N826.pdf.
38. ↑ "Mobile Phone As Home Computer". http://philip.greenspun.com/business/mobile-phone-as-home-computer.

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