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From: gabe@sirius.ctr.columbia.edu (Gabe Wiener)
Newsgroups: comp.dcom.telecom
Subject: Re: What Happens When a Phone Hangs Up?
Message-ID: <telecom-v09i0447m09@vector.dallas.tx.us>
Date: 14 Oct 89 15:38:50 GMT
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In article <telecom-v09i0445m08@vector.dallas.tx.us> rmadison@euler.berkeley.
edu (Linc Madison) writes:

>In a reply to the question about answering machines detecting hang-ups,
>someone mentioned the CO switch providing "reliable CPC."  What is CPC?

I believe that CPC is "Calling Party Control," an electrical signal of
some sort that the CO can send down the line to signal when the caller
has hung up.  The benefits of this are obvious.  An answering machine
can now tell immediately when a person has hung up, rather than having
to listen for 10 seconds of silence.


Gabe Wiener - Columbia Univ.     "This 'telephone' has too many shortcomings
gabe@ctr.columbia.edu             to be seriously considered as a means of
gmw1@cunixd.cc.columbia.edu       communication. The device is inherently of
72355.1226@compuserve.com         no value to us."  -Western Union memo, 1877