Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!cbatt!ucbvax!tektronix.tek.COM!gary%percival%reed From: gary%percival%reed@tektronix.tek.COM.UUCP Newsgroups: mod.telecom Subject: Re: Submission for mod.telecom Message-ID: <475@percival.UUCP> Date: Thu, 19-Mar-87 20:32:55 EST Article-I.D.: percival.475 Posted: Thu Mar 19 20:32:55 1987 Date-Received: Sun, 22-Mar-87 18:18:45 EST References: <8703130415.AA22972@seismo.CSS.GOV> <17897@ucbvax.BERKELEY.EDU> Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: Gary Wells Distribution: world Organization: Percy's UNIX, Portland, OR. Lines: 10 Approved: telecom@xx.lcs.mit.edu Summary: Telco line testing stratagies There are several methods used by the telco's for line testing. The simplest is that all cables have a known (very precisely) resistance and capacitance per foot. If a short is applied at the end of a cable (or a known resistance, etc), then a calibrated ohmmeter can tell you how far away the short is. If you are looking at a clean open, you can apply the same principle with a capacitance meter (though, in practice, it is not as accurate). By knowing WHAT is hanging on the end of your cable, you can quickly tell the status of the pair AND the station. This is why the telco's fought so hard about registration. They really didn't care about the equipment, they just need to know what it "looks" like, for trouble isolation purposes.