Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!sun-barr!texsun!texbell!vector!telecom-gateway From: dmntor!steve@dmnhack.uucp (Steve Pozgaj) Newsgroups: comp.dcom.telecom Subject: Re: NNX, N1X, N0X etc. Message-ID: Date: 9 Jun 89 12:56:15 GMT Sender: news@vector.Dallas.TX.US Reply-To: steve@dmntor.UUCP (Steve Pozgaj) Organization: Digital Media Networks Inc. Toronto, Ontario, Canada Lines: 10 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 194, message 5 of 9 The reason for NNX vs. XXX or NNN is that the N's designate one of a set of specific digits, while the X's designate *any* digit. Thus, a phone number is stated as NPA-NNX, with no care to the last 4 digits, since they can be anything. The N's just mean "more important to watch how these are selected", while the X's mean "pick whatever you want". The NPA (Number Plan Area code) is *real* special, so has its own name. Of course, N1X and N0X do convey the spirit of "pick the first one carefully; the middle one must be 0 or 1, and the last one's no big deal. (At least that's what I was told in a telephony course when I worked at Northern Telecom some 12 years ago.)