Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!ll-xn!oberon!sdcrdcf!csun!polyslo!dorourke
From: dorourke@polyslo.UUCP (David O'Rourke)
Newsgroups: comp.protocols.appletalk
Subject: Re: PhoneNet cabling
Message-ID: <3090@polyslo.UUCP>
Date: 5 Jun 88 21:33:22 GMT
References:  <614@mtxinu.UUCP> <3611@saturn.ucsc.edu>
Reply-To: dorourke@polyslo.UUCP (David O'Rourke)
Organization: Cal Poly State University -- San Luis Obispo
Lines: 23

In article <3611@saturn.ucsc.edu> eshop@saturn.ucsc.edu (Jim Warner) writes:
>No.  Apple's LocalTalk is RS-422 balanced differential signalling.

  I was under the impression that differential signalling requires two wires
for each signal.  So that would require Apple's LocalTalk to use 5 wires, 2
for Transmitt, 2 for Recieve, and 1 for ground.  Well LocalTalk only has 3
wires, 1 transmit, 1 Recieve, 1 ground.  Besides I was told by an EE person 
who looked at Apple's Transformer specs in inside AppleTalk that their
wiring scheme reaks more of RS-423 (RS-432??).
  In any after looking at the specs for the LocalTalk box, and the number of
wires in the LocalTalk cable, the 20 or so people I've talked to seem to think
apple isn't using the RS-422 at all.  And after looking at how they wired
the 8530 these people were even move convinced that Apple isn't using the
RS-422 standard at all, they seem to be using a tweaked version somewhere
between RS-232 & RS-422.

  In any case I might be wrong, but I don't think LocalTalk is run on top of
RS-422 as you stated.

-- 
David M. O'Rourke

Disclaimer: I don't represent the school.  All opinions are mine!