Path: utzoo!utgpu!watserv1!watmath!att!linac!pacific.mps.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!MATHOM.CISCO.COM!BILLW
From: BILLW@MATHOM.CISCO.COM (William Chops Westfield)
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: Western Digital Ethernet Cards
Message-ID: <12659564655.11.BILLW@mathom.cisco.com>
Date: 5 Feb 91 09:45:37 GMT
References: <37@eng.microplex.com>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 24


    Have you ever noticed that Western Digital Ethernet adapters have what
    appears to be a capacitor that is partially sawed through?  It's near
    the thick ethernet connector.  It might even be a varistor.  I've seen
    it on older WD8013 EBT's and on their latest (Rev B).

    Does anyone have a clue why they do this?

Hee hee.  I am pretty sure that this is a spark gap.  Most ethernet
transceivers have them, even the external boxes.  Since the WD boards
have an internal transceiver, they also have their own spark gap.

Spark gaps have interesting electrical properties.  In theory, a high
enough voltage on the cable will cause a nice spark their, before the
inductance of, say, the PC board traces, lets the voltage through to the
more sensitive components further inside your computer.

As a software sort of guy, devices with spark-gaps make me nervous.
T1 CSU/DSUs have several, like one on each incoming wire.

BBZZZZZZZZZ  ZAP!

BillW
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