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From: mwn@ufcsg.cis.ufl.EDU (Michael Nora)
Newsgroups: comp.dcom.lans
Subject: Re: Transceiver cable differences
Message-ID: <795@ufcsg.cis.ufl.EDU>
Date: Thu, 15-Oct-87 10:47:45 EDT
Article-I.D.: ufcsg.795
Posted: Thu Oct 15 10:47:45 1987
Date-Received: Sat, 17-Oct-87 18:05:04 EDT
References: <1020@hi-csc.UUCP> <167800004@uiucdcsb> <766@gec-mi-at.co.uk>
Organization: UF CIS Department
Lines: 51
Summary: The differences . . .

In article <766@gec-mi-at.co.uk>, steve@gec-mi-at.co.uk (Steve Lademann) writes

> At odd times, the fan-out
> unit sprayed random garbage onto the Ethernet, causing Havoc. The Ethernet
> on this site is fairly extensive, so finding the problem was not easy.
> ISOLAN/BICC told us that the problem was due to the cable being Series 2
> not 802.3. However, substituting a DELNI for the ISOLAN box cured the problem
> 
> Now, the net effect is that I've got the distinct impression that I've had
> the wool pulled over my eyes. Any netlander care to comment?

There are differences in the cables. We have Chipcom Broadband Ethernet modems
in use on this campus, and the following is excerpted from Technical Tip 87-003
issued by Chipcom Corp.


   There are a few subtle differences in the AUI transceiver cables in use
   today. These differences occurred because there are three Ethernet
   standards, V1.0, V2.0, and 802.3.
 
   1. In version 802.3, all shields of the individual signal and power pairs
      are connected to pin 4. The overall AUI cable shield is connected to the
      AUI connector shell to provide a cable ground. Pin 1 is not used.
 
   2. In version 2.0, all shields are connected to pin 1 and the AUI connector
      shell. Pin 4 is not used. Most Ethernet cables are built this way.
 
   3. In version 1.0, shielding of individual signal or power pairs was not
      required since most controllers and transceivers were DC-coupled. The
      overall AUI cable shield provided for shielding and grounding and was
      connected to pin 1 and the AUI connector shell. In practice, most
      Ethernet V1.0 equipment used version 2.0 cables due to cross talk
      problems created by the lack of individual shielding for the pairs.
 
   Also, since the 802.3 AUI cables provide an isolated ground shield from the
   signal and power pairs shields, these cables provide additional noise
   immunity in noisy operating environments.


Maybe the ISOLAN equipment you have requires the version 802.3 cable. All of
the DEC equipment I've seen used the version 2.0 cables. This may be why the
DELNI works and the ISOLAN doesn't. Open the shells on your transceiver
cables, and if they are grounded to pin 1, try moving them to pin 4 and see
if that cures your problem. Hope this helps out.


-- 
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Michael Nora                    Internet:  mwn@beach.cis.ufl.edu
University of Florida           UUCP:  ...{ihnp4,rutgers}!codas!ufcsv!ufcsg!mwn
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