Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!att!westmark!dave
From: dave@westmark.WESTMARK.COM (Dave Levenson)
Newsgroups: comp.dcom.modems
Subject: Re: Noisy phone lines
Message-ID: <1546@westmark.WESTMARK.COM>
Date: 20 Nov 90 04:23:36 GMT
References: <1990Nov15.193826.3875@beach.csulb.edu> <2983@hayes.uucp>
Organization: Westmark, Inc., Warren, NJ, USA
Lines: 24

In article <2983@hayes.uucp>, tnixon@hayes.uucp (Toby Nixon) writes:

> Remember -- as soon as that phone cable leaves your house, it 
> immediately goes into a big fat cable with literally hundreds or 
> thousands of other pairs of copper wire.  If "crosstalk" was going 
> to be a problem, you'd have already run into it!!

No, not exactly.  The big fat cable has individual twisted pairs
which are all twisted in such as way as to cancel the crosstalk
which would otherwise be created by induction between them.

The original question was concerned with running two voice-frequency
circuits (one of which happened to be used by a modem) in the same
piece of quad.  Quad has four wires, with no twists, and no
anti-crosstalk arrangement.  Crosstalk does occur in such cables,
but it doesn't become noticable until the cable length approaches a
hundred feet or so. (An admittedly subjective measurement ... your
mileage may vary.)

-- 
Dave Levenson			Internet: dave@westmark.com
Westmark, Inc.			UUCP: {uunet | rutgers | att}!westmark!dave
Warren, NJ, USA			AT&T Mail: !westmark!dave
[The Man in the Mooney]		Voice: 908 647 0900  Fax: 908 647 6857