Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!gem.mps.ohio-state.edu!usc!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!gryphon!vector!telecom-gateway From: nvuxr!deej@bellcore.bellcore.com (David Lewis) Newsgroups: comp.dcom.telecom Subject: Re: 8-Digit Phone Numbers vs. More Area Codes Message-ID: Date: 19 Nov 89 19:41:08 GMT Sender: news@vector.Dallas.TX.US Organization: Bellcore, Livingston, NJ Lines: 73 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 523, message 1 of 10 In article , lars@salt.acc.com (Lars J Poulsen) writes: ] In article , ] nvuxr!deej@bellcore.bellcore.com (David Lewis) writes (in ] response to a question from Peter da Silva): ] >[Even after all NPA have switched to NXX exchange codes, the remaining ] > NPA codes will be exhausted around 1995.] The ] >plan then is to go to interchangeable NPA codes -- so that the syntax ] >for a phone number will be NXX-NXX-XXXX. That will provide for 640 ] >new NPA codes, whereas there are currently 152 available N{0/1}X NPA ] >codes available. That should keep things quiet for some time, ] >considering there will be (approximately -- I haven't removed codes ] >like N00 and N11) 6.4x10^9, or 6.4 billion phone numbers available in ] >North America. ] Can this be accommodated without taking the whole system to ESS ? I ] would expect that when this happens, you will ALWAYS need to dial the ] area code, even for a local call. (Even though this may be handled by ] your instrument by then). Two questions here: (1) Can interchangeable NPA codes be implemented without replacing SXS and crossbar switches with ESS (stored-program control) switches? (2) When interchangeable NPA codes are implemented, will you always need an area code, even for a call in the same NPA? Question 1 I honestly don't know the answer to, although I would *suspect* the answer is "yes". _Notes_ (*) talks around the subject without coming out and saying it: "The cost of such conversion [accepting NXX codes as NPA codes] is largely a function of the type of switching systems involved. For example, electromechanical systems are generally more expensive to convert than electronic switching systems. The replacement of electromechanical switching systems will have a favorable impact on the cost..." For question 2, I can safely say the answer is "no". I don't want to quote two pages of text and two pages of tables (for those of you who are interested, it's sections 3.03 to 3.13 and Tables 3-C and 3-D of _Notes_...) to explain, but I'll try to summarize... The recommended standard dialing procedure for NPAs which have implemented interchangable CO codes, and for the NANP when the cutover to interchangeable NPA codes takes place, is called the "prefix method". The prefix method "... is to have the callers provide a positive indication of their intention by dialing '1' in front of the area code on all 10-digit (and only 10-digit) calls." In other words, 1+NXX indicates that the NXX is an NPA code, and NXX alone indicates that the NXX is a CO code in the same NPA. Therefore, an area code is only required, preceded by a '1', for calls outside the home NPA. (*) Notes on the BOC Intra-LATA Networks -- 1986. TR-NPL-000275, Issue 1, April 1986. My favorite reference... NPA = Numbering Plan Area, or area code. NANP = North American Numbering Plan NXX = NANP syntax for a three-digit string, {[2-9],[0-9],[0-9]} CO = Central Office. In a phone number, e.g. 765-4321, 765 is the CO code. ESS = Electronic Switching System. A switch in which the switch fabric is centrally controlled by a computer. SXS = Step by Step switch. Anyone that doesn't know what BOC means hasn't been paying attention for the past six years... David G Lewis ...!bellcore!nvuxr!deej (@ Bellcore Navesink Research & Engineering Center) "If this is paradise, I wish I had a lawnmower."