Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!uwm.edu!zaphod.mps.ohio-state.edu!tut.cis.ohio-state.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: dritchey@ihlpb.att.com (Donald L Ritchey) Newsgroups: comp.dcom.telecom Subject: Re: Centrex and 9xxx Numbers Message-ID: <4472@accuvax.nwu.edu> Date: 27 Feb 90 16:20:30 GMT Sender: news@accuvax.nwu.edu Organization: AT&T Bell Laboratories, Naperville, Il. Lines: 57 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 131, Message 7 of 8 In article <4365@accuvax.nwu.edu>, dave%westmark@uunet.uu.net (Dave Levenson) says: X-Telecom-Digest: Volume 10, Issue 128, Message 7 of 12 > In article <4112@accuvax.nwu.edu>, djcl@contact.uucp (woody) writes: >> Perhaps there are other examples of the -9xxx gap where Centrex, or >> other direct-dial extension systems are used out there... > Most Centrex groups use less than a full 10,000 numbers, and so there > are ordinary subscriber lines with numbers having the same prefix. > The 0xxx and 9xxx groups are generally not assigned to centrex, so as > to provide attendant and 'outside' access. Sometimes there are other > centrex groups with the same prefix, but members of one group must > dial 9+ 7 digits to reach members of the other. Here at Bell Labs in Indian Hill, Naperville, our CENTREX groups use all 10,000 numbers in the 708-979-xxxx range (my number is in there) as well as part of 708-713-xxxx, but we use prefix codes to distinguish between the extensions and the services that seem to conflict. For extensions, we dial 3xxxx or 9xxxx. For operator, we dial *0 (versus just 0) [left over from the days when we only had 4-digit dialing and one prefix]. For outside line, we dial *9 (versus just 9) [see previous comment]. Since most CENTREX services are based on modern digitally controlled switches, the dialing plan used for CENTREX is usually customized to some extent based on the needs of the customer. The customer can specify the needs of the application, and someone from the Telco business office gets the task of making it work. - You want 4-digit extension dialing, if you have less than 10,000 lines, you can get it. - You want 4-digit extension dialing, and you have more than 10,000 lines, then something has to give. Either you can't dial everyone with extension dialing (make outside calls to the other lines not on the same prefix (NXX)) or you go to 5-digit extensions. We did the later here. All of CENTREX is a compromise between what the customer wants done (usually pretty standard to minimize learning curves of new users) and what the Central Office switch can handle. Some switches are more flexible than others, but someone with experience in comparing different vendors offerings will have to assess which switch is "best". That is not something for the casual observer. #include Don Ritchey dritchey@ihlpb.att.com or don.ritchey@att.com AT&T Bell Labs, Room IH 1D-409, Naperville, IL 60566, (708) 979-6179 :-) The advice you get here is worth all that you paid for it. :-)