Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!zaphod.mps.ohio-state.edu!sunybcs!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: Electrical pulse on telephone lines?
Summary: Automatic Line Insulation Testing
Keywords: ring
Message-ID: <3575@kitty.UUCP>
Date: 26 Dec 89 14:05:42 GMT
References: <4208@crdgw1.crd.ge.com> <4910@blake.acs.washington.edu> <2922@mmsac.UUCP>
Distribution: na
Organization: Recognition Research Corp., Clarence, NY
Lines: 25

In article <2922@mmsac.UUCP>, jim@mmsac.UUCP (Jim Lips Earl) writes:
> Is that why my chirp-ring phone chirps ONE time around 1:10am each night?

	That's why there is one chirp.  Most ALIT apparatus uses a DC
excitation voltage between 24 and 50 volts (not necessarily the same
as CO battery, however).  Since minimizing test time per line is of
importance in the design of ALIT apparatus, the excitation voltage is
often applied of *opposite* polarity in order to rapidly counter the
telephone line capacitance.

	Therefore, the chirp is usually caused by the reversal of
polarity on the telephone line - which acts, in effect, like one cycle
of ringing voltage.

	Mechanical ringers will not respond this fast, and neither will
*well-designed* electronic tone ringers.

> How often do they do this?

	Generally, once per night.

<> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
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