Telephone Exchange Names - United States and Canada

United States and Canada

In the United States, major cities such as New York, Philadelphia, Boston and Chicago first used the 3L-4N system. They were 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. The Bell System introduced the Panel switch for large metropolitan areas, and by 1950 twenty cities were served by panel equipment. The first panel exchanges were installed in New Jersey (Mulberry & Waverley) in 1915, though they were initially semiautomatic exchanges and the customer asked an operator for the number.

Later the 3L-4N system was replaced it with the so-called 2-5 numbers or 2L-5D, two letters and five digits (though the first 3 digits still identified the local central office). 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, known as Direct Distance Dialing, came into use in the 1950s.

The standard format for displaying telephone numbers that used exchange names was to capitalize the first few letters that were dialed, for example:

• BALdwin 6828 (typical urban North American before move to two-digit exchange names)
• MArket 7032 (typical urban North American six-digit phone number, phased out in 1950s)
• MUrray Hill 5-9975 (one of the Ricardos' numbers on I Love Lucy. Note that the H in Hill, although not dialed, is still capitalized)
• ENglewood 3-1234 (typical North American, in New Jersey or continent-wide after about 1950)

In print, such as on business cards or in advertisements, the full exchange name was often abbreviated, with a period used to indicate the abbreviated form, an example being:

• TEmpleton 1-6400 would appear as TE 1-6400.

If the letters were not dialed, it was common to capitalize only the first letter of each part of the exchange name (e.g., "Metcalfe 6000" or "Fairmont 3335"). 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 dialing. 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.