Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!brutus.cs.uiuc.edu!wuarchive!swbatl!texbell!vector!telecom-gateway From: goudreau@dg-rtp.dg.com (Bob Goudreau) Newsgroups: comp.dcom.telecom Subject: Why We Have Seven Digit Numbers Message-ID: Date: 20 Jul 89 15:50:56 GMT Sender: news@vector.Dallas.TX.US Lines: 58 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 249, message 1 of 6 [Charles Buckley (ceb@csli.stanford.edu) writes: ] >As far as the Bell study is concerned, I wasn't around at the time, >but I'm sure that it had the single-digit American parochialism >built-in. Who's to say how this influenced the results? From what I understand, the Bell study was the reason that the current 7-digit system was set up in the first place. There was no American parochialism before then, because there was no standard telephone number length or format in use at the time; there was a only mish-mash of different setups. From what I remember reading, the study tested people to discover the longest number-length that could be easily remembered, and the best format for such numbers. The optimal answer they came up with was 7 digits, arranged in a 3-4 split. (Correct me if I'm wrong, you other Telecom readers who remember this better.) >They [Germany] will never run out of numbers (unlike the US). Once NXX area codes are implemented in a few years, the NANP will have on the order of 5 * 10^9 possible numbers. I hope never to have to see the day when North America has enough people to consume all those numbers! For all practical purposes, NXX-NXX-XXXX means that we'll never run out of numbers. And by the time that we need >10 distinctly addressable communications channels per person, do you think we'll still be using telephone numbers directly? >The inappropriate rigidity of the American 7-digit system is well >demonstrated on one extreme by the relatively traumatic phenomenon of >area code splitting in big cities, ... I don't see how you can use area code splitting as an example that proves the superiority of variable-length systems over fixed-length ones. It seems to me that it would be just as annoying to have my number changed from (say) 369.56.78 to 73.69.56.78 as it would be to have my number changed from (say) 617-369-5678 to 508-369-5678. You still have to get all the stationery reprinted, etc. In fact, I could argue that an area code split can be *less* traumatic overall. Consider that when Paris went to 8 digits, *everybody* in Paris had their number changed. Now consider that when New York City split 718 off from 212, *only* the people consigned to the new code had their numbers changed. The denizens of Manhattan and the Bronx (which continue to be 212) weren't inconvenienced at all. Fixed-length numbers have other advantages as well. The well-known number format is an easily-memorized template, and makes it extremely easy to notice dropped digits and such, since the result is a malformed number. Also, they can allow telco switching equipment to be used more efficiently because, once the first few digits have been entered, the length of the rest of the number can generally be calculated (excepting international calls, of course!). This means that the switching equipment doesn't have to waste time by constantly asking itself "is he done dialing?" after each and every digit is sent; it can just wait until all the digits are in. Bob Goudreau +1 919 248 6231 Data General Corporation ...!mcnc!rti!xyzzy!goudreau 62 Alexander Drive goudreau@dg-rtp.dg.com Research Triangle Park, NC 27709, USA