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From: scj@pandora.bellcore.com (Steve Johnson)
Newsgroups: misc.forsale,unix-pc.general,comp.sys.att
Subject: Re: AT&T UNIX PC 3B1s and LAN cards  FOR SALE
Message-ID: <22891@bellcore.bellcore.com>
Date: 3 May 90 17:31:33 GMT
References: <1127@netwrx1.UUCP> <29556@cup.portal.com>
Sender: news@bellcore.bellcore.com
Reply-To: scj@pandora.UUCP (Steve Johnson)
Organization: Bellcore
Lines: 24

In article <29556@cup.portal.com> thad@cup.portal.com (Thad P Floryan) writes:
... (much reasonable information deleted)
>
>Transceivers for "standard" Ethernet (the thick cable) cost either the same
>or slightly more than the ones for ThinNet; the standard Ethernet transceivers
>have the "vampire" tap that pierces the cable down to the center conductor
>(and note you'll probably need a braid pick to poke around the cable).
>
A quick caution about mechanical vampire taps---the most common.  These
are the rough equvalents to "snap on" power taps often sold to wire
trailer lights to your car's electrical system.  And just as prone to
failure due to misalignment, corrosion, etc.

Beg, borrow or steal coax strip and crimp tools if you must, but avoid
mechanical vampire taps unless you like network trouble (think about
it---You're going to pass a theoretical 10 mega-bits *per second* thru a
*pin* that pierces the coax outer cover, the outer braid, possibly an
intermediate cover and braid, and the inner sheath and then "gouging"
a mechanical connection onto the approximately 18 guage carrier wire).
The cable you're piercing is the backbone, which in commercial environments
is often the most expensive part of the LAN.  Thick ethernet cable is *tough*
stuff.  I've seen a vampire tap wrongly installed (by a non-trained
individual) literally cut the backbone in two.  (brings the LAN down
RIGHT NOW).