Voip Blog
Telephone Exchanges and Numbers
Sunday, May 18, 2008
One of the fascinating things I've uncovered digging around in Ma Bell's history is how telephone numbers have changed over the years. Up until the 1950s, numbers could be anything up to 6 digits long, depending on where you live. This didn't matter so much since, in some cases, it was not possible to directly dial, a human operator had to connect the line.
The other funny thing phone numbers had were these "exchange" names. Things like PEnnsylvania, GRamercy, DUpont. Notice that the first couple of letters were capitalized. This was to indicate which "letters" to dial on your rotary dial, which of course corresponded to numbers.
As exchange names were based on pronounceable names, it meant that some of the possible numbers ones could use for telephone numbers weren't usable. In particular, it eliminated the use of one or zero as the second digit in the exchange number. Even after converting to 7 digit telephone numbers starting in the early 1960s, it became necessary to institute all number calling.
All number calling phased in the replacement of the exchange names with numbers, meaning everyone got a 7 digit telephone number. That's what they had all along, but they lost the name that went with it. It was apparently fought against in the cities where the exchange names gave a sense of community.
Due to the growth of the phone system, they also had to change a rule about area codes. Originally, they were 3 digits of the following form: first digit could not be a one or zero, second digit had to be either a zero or one, and the last digit could not be a one or zero. Now the second and third digit can be anything!
Even with all these changes to the allowable telephone numbers, there were some other challenges we'll cover next time.
