All-number calling (ANC) is a

telephone numbering plan 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, reach ...

that was introduced into the

North American Numbering Plan The North American Numbering Plan (NANP) is an integrated telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1, World Numbering Zone ...

by 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 ...

in the United States starting in 1958 to replace the previous system of using a telephone exchange name as the first part of a

telephone number A telephone number is the address of a Telecommunications, telecommunication endpoint, such as a telephone, in a telephone network, such as the public switched telephone network (PSTN). A telephone number typically consists of a Number, sequ ...

.Blair N.D., Cosgrove M.P. (AT&T), ''why all numbers?'', Bell Telephone Magazine, Autumn 1962, p.10 The plan prescribed the format of a telephone number assigned to subscriber telephones to consist of ten digits, composed from a three-digit area code, a three-digit central office code, and a four-digit station number. This increased the number of effectively available central office codes in each numbering plan area (NPA) from 540 to 792, thereby staving off the threat of exhausting the number pool, which was forecast to occur by the late 20th century.

History

Until the 1950s, a typical telephone number in the United States and many other countries consisted of a telephone exchange name and a four- or five-digit subscriber number. The first two or three letters of the exchange name translated into digits given by a mapping typically displayed on the telephone's rotary dial by grouping the letters around the associated digit. The table (right) shows the typical assignment in the

in use at the time. The letter Q was not used, and Z was translated to 0 (zero) on some dials, albeit never used in the name system. For example, a New Yorker's telephone number might have been CHelsea 2-5034, which a calling telephone subscriber would dial as the digit sequence 2425034, translating C to 2, and H to 4. After World War II, the newly conceived nationwide numbering plan of 1947 sought to unify all local numbering plans by using a system of two central office letters and one digit to complete the office prefix, and four digits for line number. This system was referred to as ''2L-5N'', or simply ''2-5''. This plan was projected to be usable beyond the year 2000. However, with increasing demand for telephone service in the post-war decades, it became apparent by the late 1950s, that the system would be outgrown by about 1975.AT&T, ''All-Number Calling Being Introduced In Bell System'', Bell Laboratories Record 38(12) p.470 (December 1960) The limitations for the usable leading digits of central office codes, imposed by using common names for central office names, and their leading two characters as guides for customer dialing could no longer be maintained when opening new central offices. By 1962 it was forecast that in 1985 the number of telephones in the nation would equal its population of 280 million and increase to 600 million telephones for 340 million people in 2000.Blair N.D., Cosgrove M.P. (AT&T), ''why all numbers?'', Bell Telephone Magazine, Autumn 1962, p.10 As a result, the North American telephone administrations first introduced letter combinations that could not be linked to a familiar pronounceable central office name in some highly populated states, such as New York. The final solution to the growing threat of numbering exhaustion was decided by AT&T engineers and administrators from in-depth studies of all alternative methods. It was decided to eliminate the restrictions of using names and lettered prefixes. This goal had been envisioned internally within AT&T for some time. In 1954,

John Karlin John Elias Karlin (February 28, 1918 – January 28, 2013) was an industrial psychologist and a pioneer in human factors engineering at Bell Laboratories of AT&T. As the son of grocers, Karlin was born in Johannesburg, South Africa. He studied ...

directed a research project that investigated the memory capacity and dialing accuracy of employees when using seven-digit telephone numbers comprising only digits.AT&T, ''All-Number Calling Being Introduced In Bell System'', Bell Laboratories Record 38(12) p.470 (December 1960) At that time, some directory publishing departments also began removing the entire central office name from telephone directories, preferring to only list the dialed letters of the prefix. The practice did not produce any adverse effects,Brooks J., ''Telephone: The First Hundred Years'' (1976) , p. 271 and opened the path for listing telephone numbers in the ''2-5'' style, where the two letters were unrelated to any pronounceable name. Under all-number calling, the number of permissible central office prefixes increased from 540 to potentially 800, but the first two digits of the central office code were still restricted to the range ''2'' to ''9'', and the eight combinations that ended in ''11'' were reserved as special calling codes. This increased the numbering pool for central office codes to 640, and resulted in the partitioning of the prefix space (''000''—''999'') according to the table at the right. All-number calling was first field-tested in

Wichita Falls, Texas Wichita Falls ( ) is a city in and the county seat of Wichita County, Texas, United States. It is the principal city of the Wichita Falls metropolitan area, Wichita Falls metropolitan statistical area, which encompasses all of Archer County, Tex ...

starting on January 19, 1958, with the installation of a new dial exchange. The results indicated a substantial reduction of dialing errors over new system installations that used the ''2-5'' numbering system. In small communities the new system was met with little resistance. In

Council Bluffs Council Bluffs is a city in and the county seat of Pottawattamie County, Iowa, Pottawattamie County, Iowa, United States. The population was 62,799 at the 2020 United States census, 2020 census, making it the state's List of cities in Iowa, te ...

, Iowa with roughly 26,000 telephone subscribers, it also caused no major resistance in March 1960. During larger scale introductions in California in 1962, this change sparked an intense outcry among urban users who considered all-digit dialing to be dehumanizing. Karlin, the inventor of the all-number system, stated that he had been approached by a woman at a cocktail party, "Are you the John Karlin who is responsible for all-number dialing?" He proudly replied, "Yes, I am." She then asked him, "How does it feel to be the most hated man in America?" Opponents created a variety of organizations to oppose all-number calling, including the Anti-Digit Dialing League and the Committee of Ten Million to Oppose All-Number Calling to pressure

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 ...

to drop the plan.Simon Romero.
Now You Need an Area Code Just to Call Your Neighbors.
''New York Times,'' May 7, 2001. Other countries introduced similar transitions for eliminating exchange names. In the United Kingdom, the new system was known as

all-figure dialling All-figure dialling was a telephone numbering plan introduced in the United Kingdom starting in 1966 that replaced the traditional system of using initial letters of telephone exchange names as the first part of a telephone number. The change affect ...

References

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External links

A Capsule of History of the Bell System
Telephone numbers Telephone numbers in the United States

History

See also

References

External links