Path: utzoo!utgpu!watserv1!maytag!xenitec!zswamp!root
From: root@zswamp.fidonet.org (Geoffrey Welsh)
Newsgroups: comp.dcom.modems
Subject: Twisted pairs, was: Noisy phone lines
Message-ID: <5072.274CAD24@zswamp.fidonet.org>
Date: Thu, 22 Nov 90 18:23:10 EST
Organization: Izot's Swamp BBS - Kitchener, Ontario

David Lesher,,255RTFM,255rtfm (wb8foz@mthvax.cs.miami.edu ) wrote:

 >All this Chubby Checker work is to cancel out the influence of external
 >magnetic fields. I can remember seeing the proof in fields class, but
 >my memory blissfully shields {booo} me from the gruesome details.

   Short & simple version: picture the pair, connected at each end to some 
kind of device, as a loop. The interference picked up is proportional to the 
electromagnetic flux passing through the loop. Twisting the loop reduces the 
area to negligible.

   That's why signal wires should be twisted with their returns (read "ground" 
where appropriate).
 

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