Advantage: This plan avoids two SxS taboos: subscriber numbers beginning > with 0 or 1:
> - Initial 0 is taboo because "experience has shown that in a single-
> office system it is not advisable to use subscribers' numbers
> commencing with the numeral zero (0) unless absolutely necessary
> to secure the desired capacity" [1]. And, of course, zero is
> traditionally used to reach the local operator, if any.
> - Initial 1 is taboo because an SxS (or any other rotary-dial) switch
> can't distinguish between an intentionally-dialed 1 and a false
> switchhook depression.
> Disadvantage: It's not possible to match subscriber numbers to apartment
> numbers (although, as PAT notes, this might not be a good idea anyway).
> [1] Kempster B. Miller. "Telephone Theory and Practice" vol. 3
> "Automatic Switching and Auxiliary Equipment." New York: McGraw Hill, > 1933, p. 129.
> Neal McLain
The 1933 citation you mention, which I read in the 1940s, was really my introduction to how the telephone and telephone systems works, and definitely piqued my interest in the field.
However, the 1 as initial digit taboo was reserched thoroughly when DDD was extended to customers through CAMAs in largely step-by-step exchanges, particularly in large cities that were primarily step-by-step.
I forget how many million actually live calls were studied to determine how many of them had a false switchhook depression.
There were none. Zero. Conventional wisdom was wrong.
Wes Leatherock snipped-for-privacy@aol.com snipped-for-privacy@yahoo.com
[TELECOM Digest Editor's Note: I used to know someone who worked his away around the 'incoming calls only' rule on a telephone at the place where he lived. Although the phone did have dial tone, it also had a blank face plate, to avoid being able to dial outgoing calls, supposedly. His respose was to learn how to tap on the hook in the proper sequence and timing. Inconvenient to be sure, but it worked. PAT]