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A telephone exchange name or central office name was a distinguishing and memorable name assigned to a central office. It identified the switching system to which a telephone was connected. Each central office served a maximum of 10,000 subscriber lines identified by the last four digits of the telephone number. Areas or cities with more subscribers were served by multiple central offices, possibly hosted in the same building. The leading letters of a central office name were used as the leading components of the telephone number representation, so that each telephone number in an area was unique. These letters were mapped to digits, which was indicated visibly on a dial telephone.
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Several systematic telephone numbering plans existed in various communities, typically evolving over time as the subscriber base outgrew older numbering schemes. A widely used numbering plan was a system of using two letters from the central office name with four or five digits, which was designated as 2L-4N or 2L-5N, or simply 2–4 and 2–5, respectively, but some large cities initially selected plans with three letters (3L-4N). In 1917, W. G. Blauvelt of AT&T proposed a mapping system that displayed three letters each with the digits 2 through 9 on the dial.
Telephone directories or other telephone number displays, such as in advertising, typically listed the telephone number showing the significant letters of the central office name in bold capital letters, followed by the digits that identified the subscriber line. On the number card of the telephone instrument, the name was typically shown in full, but only the significant letters to be dialed were capitalized, while the rest of the name was shown in lower case, such as in the example image for the telephone number LAkewood-2697 in service in Lakewood, NJ (USA).
Telephone exchange names were used in many countries, but were phased out for numeric systems by the 1960s. In the United States, the demand for telephone service outpaced the scalability of the alphanumeric system and after introduction of area codes for direct-distance dialing, all-number calling became necessary. Similar developments followed around the world, such as the British all-figure dialling.
United States and Canada
In the United States, the most-populous cities, such as New York City, Philadelphia, Boston, and Chicago initially implemented dial service with telephone numbers consisting of three letters and four digits (3L-4N) according to a system developed by W. G. Blauvelt of AT&T in 1917. This system mapped the letter of the telephone number to the digits on the telephone dial. Most other major Canadian and US cities, such as Toronto and Atlanta, were converted from manual exchanges using four digits to a local 2L-4N numbering plan. For example, in Montréal, ATwater 1234 was dialed as six pulls on the dial (AT1234) to send the digit sequence 281234. Eventually, starting in the late 1940s, all local numbering plans were changed to the 2L-5N system to prepare for nationwide Direct Distance Dialing. For example, under this system, a well-known number in New York City was listed as PEnnsylvania 6-5000.
In small towns with a single central office, local calls typically required dialing only four or five-digits at most, without using named exchanges. A toll call required the assistance of an operator, who asked for the name of the town and the local station number. Some independent telephone companies, not part of the Bell System, also did not implement central office names.
In 1915, newly developed panel switching systems were tested in the Mulberry and Waverly exchanges in Newark, New Jersey. When the technology first appeared in the Mulberry exchange, subscribers had no dials on their telephones and the new system was transparent to them — they asked an operator to ring their called party as usual. However, the operator keyed the number into the panel equipment, instead of making cord connections manually. The panel switch was later, from the early 1920s through the 1930s, installed in large metropolitan areas in the Bell System. By the 1950s twenty cities were served by this type of office.
From the time of these first conversions to automated equipment in the 1920s, through the conversions of most manual equipment by the 1960s, it was necessary for telephone numbers to be represented uniformly across the nation. By Bell System policy, customers never needed to be concerned about whether they were calling an automatic or a manual exchange. The 2L-5N system became the North American standard, as customer-dialed long distance service came into use in the 1950s.
Several standard formats of telephone numbers, based on central office names, capitalized the leading letters that were dialed, for example:
In print, such as on business cards or in advertisements, the full central office name was often shown only by the two letters:
If the central office was known by a name, but no letters were dialed, it was common to capitalize only the first letter of the central office, e.g., Main 600W or Fairmont 33. Such numbers were assigned typically in manual offices, and the name would be spoken by a subscriber when requesting a destination. Often these were geographically significant names, such as the town's name.
In large cities with coexisting manual and dial areas, the numbering was generally standardized to one format. For example, when the last manual exchange in San Francisco was converted to dial in 1953, the numbers had for several years been in the format of JUniper 6-5833. JUniper 4 was automatic, but JUniper 6 was manual. To call JUniper 6 from JUniper 4, the subscriber dialed the number and it was displayed to the B-board operator at JUniper 6, and that operator would complete the connection manually. In the other direction, to call JUniper 4 from JUniper 6, the subscriber would lift the receiver and speak to the JUniper 4 operator who would in turn dial the JUniper 6 number.
During the 1950s, cities using six-digit numbers converted to seven-digit dialing. Typically, several six-digit (2L-4N) exchanges were co-located in one building already, with new ones added as old ones had filled up. After the conversion, they were combined into a new 2L-5N exchange. For example, the CHerry, FIllmore, ATwater, and KLondike exchanges might be converted to OXford 1, 3, 6, and 7. Usually customers would keep the same station numbers.
In the 1940s, the Bell System developed the North American Numbering Plan, a system of initially 86 allocated area codes which were used at first only by switchboard operators to route trunk calls between plan areas. Direct long-distance dialing by customers, using the three-digit area code and a seven-digit telephone number, commenced in the 1950s.
Standardization
In 1955, AT&T distributed a list of recommended exchange names that were the result of studies to minimize misunderstandings when spoken. The recommendation was intended for newly established exchanges, and did not mandate any renaming of existing historical names. The number sequences 55x, 57x, 95x, and 97x had no exchange names specified, as the mappings for the digits 5, 7, and 9 had no vowels, thus making it difficult finding names with those consonant combinations. As a result, those numbers were very seldom assigned to exchanges, however, KLondike was used for 55x in San Francisco and Columbus, Ohio, and WRigley 5 (975) in Chicago (Wrigley Field). On the telephone dial, letters were mapped to digits using the assignments shown in the table (right).
The following shows AT&T's recommended list of central office names in 1955, sorted by the three-digit office code, where x can be any digit.
Fictitious phone numbers starting with 55 used the fictitious exchange name KLondike (55). The letter Q was never used in the naming system, but Z was often mapped on the telephone dial to the digit 0 (zero) to facilitate dialing of Zenith numbers.
All-number calling
As demand for telephone service grew in the post–World War II period, it was foreseeable that the demand would exceed the addressing capacity of the existing system of using memorable telephone central office names as prefixes in telephone numbers. Several letter combinations had no pronounceable or memorable names and could not be used. Several North American numbering plan areas (NPAs) were divided so that more office codes became available to smaller regions. However, as the growth accelerated, the Bell System decided to implement all-number calling (ANC) and to deprecate the use of central office names to provide more central office codes to each NPA. This extended the usable numbering plan and only two area code splits became necessary between 1962 and 1981. All-number calling was phased in starting in 1958 and most areas had adopted it fully by the mid-1960s. In some areas it did not become universal until the 1980s. The Bell System published and distributed area code handbooks yearly which compiled the towns available for calling using an area code.
Experiencing significant resistance in many areas, the Bell System employed a strategy of gradual changes to ease the transition for customers. Originally, directory listings were printed with the central office name spelled out in full, e.g.,
The first stage in the conversion only the dialed letters were printed:
At this stage, the telephone companies had the means to assign letter combinations for central office prefixes that were previously unavailable, thus any set of five- or fewer-digit numbers could be expanded to seven digits:
At this stage all central office codes could be easily converted into their numerical format:
The Bell System proceeded to convert existing named exchanges to all-number calling, starting in smaller communities. No significant opposition arose until conversion began in major cities. In some cities such as San Francisco, opposition was organized; the opposition group in San Francisco was called the Anti Digit Dialing League, of which S. I. Hayakawa was a notable member. The opposition caused AT&T to slow down the conversion process, and names continued to be used in cities such as New York, which went to ANC only in 1978. Philadelphia had named exchanges in the Bell of Pennsylvania telephone book as late as 1983, long after AT&T had hoped to complete the conversion.
Bell Canada, Alberta Government Telephones, and B.C. Tel completed most conversions of existing numbers during the first half of the 1960s. In Toronto, historically 2L+4N before numbers were lengthened to accommodate the 1957 introduction of direct distance dialling, the March 1966 directory had no exchange names. Typically in larger communities, conversions would be timed with issues of the telephone directory.
For example, in London, Ontario, three conversions took place starting in February 1962 and completing in September 1963. GEneral 2, 3, and 9 were converted first; later GLadstone 1 and 5, and finally GEneral 4 and 8. An example from Montreal, Quebec, extended from 2L+4N to 2L+5N on August 4, 1957: WIlbank became WEllington 2, WEllington became WEllington 3 (a rare example of keeping the exchange name), FItzroy became WEllington, GLenview became WEllington 7, VEndome became DUpont 7, HEmlock became POntiac 7, TRenmore became POntiac 8, HArbour became VIctor 5, and MArquette became VIctor 9.
The use of letters in exchange names resulted in the placement of letters on the telephone dial, even outside the areas using the letter and number combinations. Some Canadian areas at first used original letter schemes, notably Calgary, Alberta, until later standardization within North America. Québec exchange names differed from those on standard Bell System lists due to the need for names in the French language; Hull, Quebec's 1-819-77x (PR as in PRovince) needed to be recognizable in both languages in 1957.
In smaller communities with four- or five-digit numbers and a single city exchange, central office names appeared for the first time in the late 1950s, and then solely to match the North American direct distance dial standard of a three-digit area code and seven-digit local number. The names, usually chosen from standard Bell System lists, had no local significance and were short-lived; phase-out began soon after 1960.
Europe
Virtually every telephone exchange in Europe was named after its local area (village, town or city). However, in the very largest cities it was clear as early as the 1880s, that several exchanges would be needed. These were usually given names reflecting a district of a city, for example Holborn in London, Docks in Manchester, Leith in Edinburgh, or in some cases an entirely artificial name, e.g., Acorn or Advance in London, Pyramid in Manchester, and Midland in Birmingham. As automated systems were introduced starting in the late 1920s, the first three letters of these names where used for dialing a number on those exchanges. The 3L-4N systems was notably used in the capital cities Paris and London, both examples of the big-city problem, with a large city served by many manual exchanges, which could only be converted to automatic gradually, and necessitating operation with a mixture of manual and automatic exchanges for some years.
Telephone directories showed the first three letters of the exchange in bold capital letters if all seven digits were to be dialed. For example, a subscriber number for Scotland Yard on London's Whitehall exchange was shown as "WHItehall 1212".
If the first three letters were capitalized but not bolded, e.g., HAYes 1295, the caller would dial the first three letters only, and when connected to Hayes ask the operator for the local number. Later, Coded Call Indicator working equipment was installed at some manual exchanges so that the caller could dial all seven digits, and the required number would be displayed to the operator.
In the United Kingdom, the first Director exchange in London, Holborn Tandem, was cutover in 1927; preceded by any necessary changes in the London area, e.g. changing some exchange names and making all local numbers (4N) 4-digit. As each digit represents three letters the same network cannot have exchanges called BRIxton and CRIcklewood, which both correspond to 274. In smaller director areas some A-digit levels were combined so that local director exchange would only need four or fewer groups of directors instead of eight. But if (say) A-digit levels 7 and 8 were combined it would not be possible to have both PERivale and TERminus exchanges in the same network.
The other main UK conurbations followed suit, namely Manchester in 1930 (e.g., DEAnsgate 3414, the number for Kendals department store), Birmingham (in 1931), Glasgow (in 1937), and later Liverpool and Edinburgh (c. 1950).
The standards for converting exchange name letters in Europe varied, notably in the placement of the letters O, Q, and Z.
The switchover to all figure dialling began in the UK in 1966, although it was not until the early 1970s that all exchange names were converted.
In Paris and its suburbs, the conversion from 3L-4N to all numbers occurred in October 1963. For example, ÉLYsées became 379, LOUvre 508, PIGalle 744, POMpadour 706... But until October 1985, when an 8th number was added, it remained possible to make use of almost all the previous combinations.
In popular culture
At least four popular songs use old telephone exchanges in their names: "PEnnsylvania 6-5000" (PE 6-5000), recorded by Glenn Miller (the inspiration for that song, the Hotel Pennsylvania in New York City, still holds that phone number as +1-212-736-5000); "BEechwood 4-5789", by The Marvelettes; "LOnesome 7-7203 by Hawkshaw Hawkins; and "ECho Valley 2-6809" by The Partridge Family. PEnnsylvania 6-5000 was later spoofed in the Bugs Bunny cartoon Transylvania 6-5000 and the horror/comedy film Transylvania 6-5000.
The title of BUtterfield 8, the 1935 John O'Hara novel whose film adaptation won Elizabeth Taylor an Academy Award for Best Actress, refers to the exchange of the characters' telephone numbers (on the Upper East Side of Manhattan). Radio show Candy Matson, YUkon 2-8209 first aired on NBC West Coast radio in March 1949.
Artie Shaw and His Gramercy 5—Artie Shaw named his band the Gramercy Five after his home telephone exchange in Greenwich Village. In 1940 the original Gramercy Five pressed eight records, then dissolved this band in early 1941.
In episode 9F07 of The Simpsons, "Mr. Plow", in which Homer takes up work as a snow-plow operator, the ad he takes out on television shows the Simpsons' phone number as Klondike 5-3226.
Stan Freberg, on his 1966 album, Freberg Underground, objected to all digit dialing in song, including the lyric:
Allan Sherman parodied the controversy of all digit dialing in the song "The Let's All Call Up AT&T and Protest to the President March" in his 1963 album My Son, the Celebrity.
Chuck Berry’s 1964 rock-n-roll hit, Promised Land, references “Los Angeles give me Norfolk Virginia, Tidewater four ten O nine” TW4-1009, when he arrives after a planes, trains and bus odyssey across the United States and calls home.
Hee Haw (1970’s television musical variety show) featured monotoned straight man Junior Samples and his weekly automobile special at Samples Motors using the phone number gag “BR-549”.