How to closed zero dial in this phone set
phone circuits included electromechanical relays which imposed limitation on the speed of dialing a digit, and therefore dialing a complete 10-digit telephone number could take up to ten seconds, during which hardware resources had to be dedicated to a circuit. The Bell System organized the numbering plan to minimize the cost of providing automatic dialing to large population centers. The second digit of all area codes was 0 or 1, while the second digit of the exchange triplet was never 0 or 1, thus facilitating the recognition of whether a user was dialing a full 10-digit number or merely dialing within the local area code. In this coding scheme it was not yet necessary to dial a leading 1 for access to long distance circuits to other area codes. In some regions, local numbers were 7 digits, or occasionally less, but a toll call within the area code required a preceding 1. Area code 617 in eastern Massachusetts used this system in the early 1970s, while the Chicago area (312) did not. In the Chicago area, one could call the Boston area by dialing only 10 digits, while in Boston, to call Chicago, one would be required to use 11 digits, including the prefix 1.
Dec 19, 2013 |