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Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!cbosgd!mark
From: mark@cbosgd.UUCP (Mark Horton)
Newsgroups: net.lan
Subject: Re: Ethernet cable length query - (nf)
Message-ID: <1151@cbosgd.UUCP>
Date: Sun, 25-Mar-84 14:25:27 EST
Article-I.D.: cbosgd.1151
Posted: Sun Mar 25 14:25:27 1984
Date-Received: Mon, 26-Mar-84 20:36:34 EST
References: <2832@fortune.UUCP>
Organization: AT&T Bell Laboratories, Columbus
Lines: 33

I am very grateful for all the replies.  What's been posted summarizes
the situation pretty well.  (Yes, we know the limit is 500 or 1K or 2.5K
meters, depending on who you talk to and what kinds of repeaters you
use, but we happen to only need 500 feet.)

Another interesting question has come up here.  The type of tap.
We have Interlan "vampire" taps.  I've been told that the 3-Com
tap, which you screw in between two cable segments, is much better.
Since our taps currently don't seem to work (probably a bad
drilling or improperly installed tap, the directions were pretty
poor when it came to specifying how far to tighten down the clamp
("do not overtighten" indeed!) and I don't know how to adjust the
other screw that controls the position of the top probe.  We also
don't know how to diagnose a bad tap - I would like to be able to
use an ohmmeter or the like to track it down but don't know what
to check.  When you're new to this game you don't necessarily know
what you are doing.  I was quite surprised to find that plugging
in the tap to the board on our 750 causes the 750 to reboot.  This
is not true of our 730.  Does this mean the 750 tap is shorted or
something like that?

Others seem to feel that vampire taps are wonderful.  The major
advantage I can see is that with 3-Com taps, you have to cut the
cable (or at least unscrew it) to add a new tap, which takes the
network down.  I gather that DEC sells vampire taps.  Does anybody
except 3-Com sell the screw-in type?  I'd be interested in opinions
on which type is better and who to buy them from.

I can say one thing for sure - going up in the ceiling and drilling
into ethernet cable with these heavy duty cables and boxes is a
gigantic pain in the wazoo.

	Mark