Remember THESE phones?

[TheBlackAdder]

92. Back in the 60s and 70s, your phone had an exchange, neighbors could be wired to another one.

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When you jumped from one exchange to another, or one central office to another, it went from a local call to a toll call.

Your phone books would have the various xxx-#### , xxx portions listed as what is local. The problem was that some of those xxx numbers could be split between two exchanges and you only find out it was a toll call when you got your phone bill.

It's a mistake you only make for the first month.

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.

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.[1]

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.

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.

https://en.wikipedia.org/wiki/Telephone_exchange_names

If you read down further, urban and suburbs of cities were late and some of the old structures carried into the early 80s.


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