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Path: utzoo!watmath!clyde!akgua!sb1!mb2c!aat!sleat
From: sleat@aat.UUCP
Newsgroups: net.misc
Subject: Re: Phones that go chirp in the night
Message-ID: <290@aat.UUCP>
Date: Wed, 4-Apr-84 11:40:17 EST
Article-I.D.: aat.290
Posted: Wed Apr  4 11:40:17 1984
Date-Received: Sat, 7-Apr-84 01:48:03 EST
References: <7437@watmath.UUCP>
Organization: Ann Arbor Terminals
Lines: 29

<Is this trip necessary?>

I have a phone which has no ringer or normal hookswitch, but is always
connected to the line through a capacitor.  Often there will be a loud
CLICK somwhere between 03:08 and 03:11 (not every night it seems).  It
is quite definitely something happening directly on my line, rather than
crosstalk.  Once it has gotten my attention, if I listen closely I can
hear the crosstalk from similar pulses being applied to other lines.

I can only conclude that the central office automatically tests lines
for something on a regular basis.  The question, is what are they testing
for?  Since they can no longer get upset about unauthorized equipment
being connected, perhaps they are just checking line impedance for
evidence of cable degradation.  I wonder if they do it only at night.
I can see two reasons why they might.  One is to minimize the annoyance
from chirping phones.  The other is that they might have problems with
normal traffic, in that it would take a more complex algorithm for the
system to work it's way around active lines and still do a complete test.

Someday I'll hang a storage scope on the line and see what the pulse really
looks like.  I have noticed that the pulse duration is not constant, but
that doesn't shed too much light on what the measuring process really is.

Doesn't anyone out there actually work for a CO on this kind of stuff?

Michael Sleator
Ann Arbor Terminals
{cbosgd|mb2c|uofm-cv|psu-cs}!aat!sleat