vern@zebra.uucp (07/22/89)
In article <telecom-v09i0196m06@vector.dallas.tx.us>, nvuxr!deej@bellcore. bellcore.com (David Lewis) writes: > In article <telecom-v09i0189m05@vector.dallas.tx.us>, ficc!peter@uunet.uu.net > writes: > > I'm curious about this terminology. Why two symbols for unspecified > > digits, here? Why N1X rather than N1N or X1X? And why NXX rather than > > any other combination on Ns and Xes? Does this mean anything, or is it > > just traditional? > I don't know why 0/1 were chosen as the special numbers; it may have > been tradition or it may have been some operations research whiz at Bell > Labs doing some T&M studies... When mechanical switching was introduced to replace operators, the equipment was sensitive to contact bounce when phone sets went off hook. This caused the step by step switches to advance one notch. To accommodate the contact bounce, the first '1' received was discarded. This eliminated the use of the '1' in an exchange name. The alpha characters were then assigned to the numerals '2' through '9' and yes, the early dials had a 'Z' on '0'. Since this mechanical equipment was a replacement for the more personable operator systems, many subscribers resented dealing with a machine just as many today resent dealing with answering machines. The need for a quick access to a living person was recognized and so a special code was given to 'Operator". Even though '1' could not be used as an exchange mnuemonic, it was used for special telephone company services such as information and repair service. ( At this time in history, the motto of Ma Bell was "Service is our only product.", since then the MBA's and LLD's have replaced that concept with "How can we get maximum profits." ). This was accomplished by doubling the '1' into '113' and '114'. Other '11N' codes were used for test purposes such as 'ring back', 'dial speed' and 'line quality'. For some reason, these codes were reversed into the '611' etc. that are used as a standard today. I think that these were a feature of the infamous 'frame' switch. Since many of these switches were installed in populace areas, the step by step's had to be modified when a national standard became desirable. When Direct Distance Dialing was conceived, this lack of the '1' and '0' in local exchanges was noted. Since they still had local importance as first digits, they were placed in the second position. This was used to 'flag' the equipment that the number being dialed was an area code and that the call should be connected to the long lines equipment. As a side note, the area codes easiest to dial on a rotary dial were assigned according to the amount of incoming traffic at the time. Thus '212' was given to New York City and '213' to Los Angeles etc. It was also at this same time that Ma Bell went from the named exchanges to full numeric in order to use some combinations which were impossible with mnuemonics. I hope that this piece of historical trivia will enlighten some readers. Vernon C. Hoxie {ncar,nbires,boulder,isis}!scicom!zebra!vern 3975 W. 29th Ave. voice: 303-477-1780 Denver, Colo., 80212 ( TB+ ) uucp: 303-455-2670 [Moderator's Note: Thank you for an *excellent* presentation! PT]