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Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!dual!paul
From: paul@dual.UUCP (Baker)
Newsgroups: net.dcom
Subject: Re: UUUUUUUUUUUUUUUUUUUU -- maybe an answer?
Message-ID: <533@dual.UUCP>
Date: Tue, 29-May-84 02:05:34 EDT
Article-I.D.: dual.533
Posted: Tue May 29 02:05:34 1984
Date-Received: Wed, 23-May-84 19:49:54 EDT
References: <4644@amd70.UUCP> <485@decvax.UUCP> <5809@mcvax.UUCP>
Organization: Dual Systems, Berkeley, CA
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>>....a once-per-second garbage character, regular as clockwork.
>>....the transmission-line hardware "steals" an 8-bit datum
>>for resyncronization.

>I don't think that's the explanation. At least on international (and
>maybe too on cross-country) lines a very low pitched note is used for
>pulse (tick) counting for connect duration timing. The interval between
>ticks depends on the distance over which the call is made. 

I have to disagree with this proposition.  Although almost all European
calls are (very sensibly) charged by "ticks", almost no U.S. calls are
charged in this way.  Typically one is charged x dollars per minute.
For the U.S., where a fair percentage of connections are digital the
first explanation is pretty sensible.  The Bell System, now ATT, is
supposed to be all locked to a master clock generator in some
unheard of town in the centre of the country.  Alternative carriers
such as MCI and SPRINT usually can't be bothered to supply passable
voice quality, so niceities like synchronizing all their clocks
would never occur to them.

In Europe, so that one can have an instant measure of billing,  it is
common to put a "common mode" signal on the line for every "tick" of
charge recorded at the exchange.  If there is some imbalance in the
connection between the exchange and the telephone, these pulses can
be heard as a faint buzzing noise.

		Paul Wilcox-Baker