When dial service was introduced (typically during the period of 1910 to 1960) in such multiple exchange communities, typically, customers would dial the first two or three letters of the exchange name, followed by the numeric digits.
Two of the most notable cities using the first three letters, four digits system, known as 3L-4N or the Director telephone system, were Paris, France and London, England, which introduced it in 1922. For example a subscriber's number on Whitehall exchange was shown in the directory in bold caps, thus: "WHItehall 1212" (the number of Scotland Yard). The other main UK conurbations followed suit - namely Manchester in 1930 (example DEAnsgate 3414 - the number for Kendals department store); Birmingham (in 1931); Glasgow (in 1937), and later Liverpool and Edinburgh. While Director automatic switching was being rolled out across the major cities, some exchanges in their areas were still manual, and the subscriber's directory entry had the exchange name in caps but not bold - for example "SANderstead 1234"; the caller then dialed the "SAN" and asked the operator for the number - 1234 in this case.
The switchover to All figure dialling began in the UK in 1966 following the successful conversion of telephone numbers in Paris, in 1963, which until then had also used the 3L-4N combinations, famously for example at POMpadour (which represented the numbers 706); LOUvre (later 508), and PIGalle (which was replaced by 744).
The United States used a similar but slightly different variation. New York, Philadelphia, Boston and Chicago first used the 3L-4N system but replaced that with the so-called "2-5 numbers" or 2L-5D, two letters and five digits (for example a number on the Pennsylvania exchange would be shown as PEnnsylvania 6-5000). This became the North American standard as customer-dialed long distance service (Direct Distance Dialing) came into use through the 1950s.
As demand for phone service grew, the supply of assignable phone numbers began to dwindle, and several North American area codes were split to enable reuse of numbers. As the growth accelerated, the decision was made to switch to All-Number Calling (ANC), since there were several unpronounceable letter combinations that were not being used. This allowed more efficient use of the number supply; only two area code splits were necessary between 1962 and 1981. All-Number Calling was phased in slowly from 1958. Most areas had adopted it fully by the late 1960s, though it did not become universal until the 1980s.
The standard format for displaying telephone numbers that used exchange names was to capitalize the first few letters if they were dialed. Some European examples were given above; in the US, examples include:
If they were not dialed, it was more common to capitalize only the first letter of each part of the exchange name, e.g.,
Such numbers could be of non-standard length, simply because they were not dialed, but quoted to an operator who plugged into the appropriate line.
During the 1950s, cities using six-digit numbers migrated to seven-digit. Typically, several six-digit exchanges were co-located in one building already, with new ones added as old ones had filled up. They were then combined into a new seven-digit number exchange. An example from Montreal, Canada, on August 4, 1957:
The use of letters in exchange names resulted in the placement of letters on the telephone dial, even outside the areas using the letter/number combinations. Some areas at first used original letter schemes (notably Calgary, Alberta) until later standardization. Europe and North America differ in placement of the letter O, and countries with non-English languages differ again.
AT&T employed a gradual strategy to ease the transition for the customers. Originally, directory listings were printed with the exchange names spelled out in full, e.g.
First stage was to print only the dialed letters:
Second stage was to assign an unpronounceable combination in communities being converted from five- or fewer dialed digits to seven; no name was associated with the letters:
Third stage was to assign ANC to smaller communities converting to seven-digit numbers.
AT&T then proceeded to convert existing named exchanges to ANC, 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 forced AT&T to slow down the conversion, and names did not totally disappear in major cities until 1975, long after AT&T had hoped to complete the conversion. Even today, however, it is not uncommon in New York City to see a new panel truck with a telephone number such as "JA 6-xxxx" painted on its side.
Bell Canada, Alberta Government Telephones and B.C. Tel completed most conversions of existing numbers during the first half of the 1960s. 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.
At least two popular songs use old telephone exchanges in their names: "PEnnsylvania 6-5000" (PE 6-5000), recorded by Glenn Miller; and "BEechwood 4-5789", by The Marvelettes. The former name was later spoofed in the Bugs Bunny cartoon Transylvania 6-5000.
Comic singer Allan Sherman includes a song, "The Let's All Call Up AT&T and Protest to the President March" on his 1963 album "My Son, the Celebrity." In this song he suggests that people take their protest against all-digit dialing straight to the top.
Satirist Stan Freberg included a sketch on the conversion to all-number calling on his 1966 album "Freberg Underground Show #1" (Capitol Records T/ST-2551), with the song "They Took Away Our Murray Hills."
In the 1980 film, The Blues Brothers, several examples of "old style" exchange numbers can be seen, such as on the business card handed to the men's-only hotel clerk by a police officer. This suggests that even as late as the early 1980s, the move away from exchange names was not yet 100% complete.
The Simpsons often shows the title family's number as KL-5 xxxx (it has been quoted differently in various episodes), which follows the convention of using 555 numbers in fictitious TV and film portrayals.
Similarly, in Seinfeld the characters often give telephone numbers beginning with KL-5.