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From: witters@tc.fluke.COM (John Witters)
Newsgroups: sci.electronics
Subject: Re: Electrical pulse on telephone lines?
Keywords: ring
Message-ID: <13302@fluke.COM>
Date: 15 Dec 89 17:24:27 GMT
References: <4208@crdgw1.crd.ge.com> <4910@blake.acs.washington.edu> <42002@improper.coherent.com>
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In article <42002@improper.coherent.com> dplatt@coherent.com (Dave Platt) writes:
>This was discussed in comp.dcom.telecom some time ago.  As I recall,
>the explanation is that the telco sends a measured voltage pulse down
>the phone lines periodically.  By measuring the current flow and
>certain other things, they can check the quality of the phone line
>and detect some physical problems as they develop (e.g. insulation
>failure, etc.).  The phone-switch in your central office does this
>automatically, at a time when the line is idle (usually late at night),
>and enters a trouble-report in the database if anything unusual
>is detected.

Of course, one of the physical "problems" that can be detected is whether there
is more than one bell connected to your phone line.  The Phone Company (tm)
probably used this technique to find out about "illegal" extension phones in
the bad old days when TPC had a monopoly on all phone equipment.  Now days,
since you don't have to lease your phones from TPC, they probably don't care
how many phones you have attached to your line.  The only thing TPC cares about
is whether your equipment will damage TPC's equipment.

-John

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