In reply to:
I recall most if not all area codes had 0 or 1 as the middle digit ~ 212 for NYC, 206 for Seattle & Western WA, 509 for Eastern Washington, 503 for the whole of Oregon, 213 for LA, 406 for Montana... you get the idea, and I'm out of memory-based examples. The power time/rotary explanation offered for prefix logic was fascinating to me - but I'm still curious about this pattern for area codes that I perceived back in the 70s. Any rationale anyone knows of for this?
Until the last decade, all area codes, and only area codes, had a 0 or a 1 as the middle digit; this convention allowed the phone exchange system to recognize an area code and differentiate it from an exchange. One of the reasons we must now dial the area code when calling long distance intra-LATA as well as inter-LATA is that the number of area codes now needed exceeds the number of permutations which can be obtained using just 0 or 1 as the middle digit.
-- Sparteye, who has had to read too many utilities regulation cases
