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Fwd: Telephone Exchange Names [telecom]

I came across this article in Wikipedia: hope it's of interest.

During the early years of telephone service, communities that required more than 10,000 telephone numbers, whether dial service was available or not, utilized exchange names to distinguish identical numerics for different customers.

When dial service was introduced (typically during the period of 1910 to

1970), in such multiple exchange communities, customers would normally dial the first two or three letters of the exchange name, followed by the numeric digits.

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Reply to
Bill Horne
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The "Director Telephone System" in London was not directly put in to provide 3L-4N numbers. That resulted from growth, which resulted in complicated trunking systems in a mostly all-step environment, resulting in the adoption of "Directors" (called senders in the Los Angeles area and installed for the same reason in that all-step area). The 3L-4N convention was what London adopted, and also adopted in many places in North America, but merely a typographical device, since the actual pulsing is of course numeric.

The article also says the first letter of exchange names was capitalized even where it was not dialed, suggesting that was the only case. In Dallas and Houton, and perhaps other places, the first letter (capitalized) WAS dialed.

Wes Leatherock snipped-for-privacy@yahoo.com snipped-for-privacy@aol.com

Reply to
Wes Leatherock

[Moderator snip]

One of the other reasons for different prefixes for Kansas and Miassouri customers was so long distance calls from those numbers could be properly rated as interstate or intrastate.

This occurred in many places near or on a state border with a C.O. serving customers in both states.

Wes Leatherock snipped-for-privacy@yahoo.com snipped-for-privacy@aol.com

Reply to
Wes Leatherock

The Bell System Technical Journal has an excellent 1923 article explaining machine switching (the "panel" system) for larger cities. The article includes the requirements of the switch and large city switching issues. One of the factors (among many) was to provide a transparent interface between dial and manual subscribers; that is, a dial subscriber would dial numbers to a manual exchange just as they would an automatic exchange. The desired line would be indicated by a lighted display panel on the destination manual switchboard. In this way dialing procedures would not change as manual offices were converted to dial.

In New York City, some manual exchanges had 10,500 lines; these required eight digit dialing and the panel senders were equipped to handle eight digits. Also, the party-line suffix was dialed, making for eight digits. The manual operator's display had provision for both. (See pp 80-82 in the reference below); the operator's display is in fig. 23 on pg 82.)

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Reply to
HAncock4

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