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Path: utzoo!linus!decvax!harpo!eagle!mhuxi!houxm!ihnp4!drux3!druxu!tll
From: tll@druxu.UUCP
Newsgroups: net.dcom
Subject: Re: Anyone know FCC regulations?
Message-ID: <728@druxu.UUCP>
Date: Sat, 1-Oct-83 11:02:00 EDT
Article-I.D.: druxu.728
Posted: Sat Oct  1 11:02:00 1983
Date-Received: Sun, 2-Oct-83 15:55:44 EDT
References: <810@hou5e.UUCP>, <894@watcgl.UUCP>
Organization: AT&T Information Systems, Denver
Lines: 23

There are several arrangements for connecting the ringers on party
lines.  One technique is to connect the ringers between tip-and-ground
and ring-and-ground.  This only selects between two ringers.  Another
arrangement is to accompany ringing voltage (normally 90VAC at 20Hz)
with a DC voltage of one or the other polarity to select ringers.  This
again limits you to distinguishing two parties.  Another technique is to
tune the ringers to different frequencies, so you can select them by
frequency.  I'm not sure how many different ringers you can select using
this method.  A fourth arrangement is to ring with different patterns,
so the humans decide from the ring if the call is for them (or if they
want to listen in).  Some of these techniques can be combined to select
a larger number of ringers.

Aside from ringing the right phone, there is the issue of billing the
right party for outgoing calls.  I'm less familiar with the techniques
used for this, but I'm sure there is similar variety.  The point is that
there are MANY different arrangements used on party lines, and almost
anything you can think of will screw up at least one of them.  That's
why nobody sells over-the-counter phone equipment for party lines.  You
don't have much choice except to go through the phone company.

			Tom Laidig
			...!ihnp4!druxu!tll