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From: jrd@cc.usu.edu
Newsgroups: comp.dcom.lans
Subject: Re: How to terminate a minimal thin ethernet segment?
Message-ID: <1991Apr6.175522.47301@cc.usu.edu>
Date: 6 Apr 91 23:55:21 GMT
References: <1991Apr5.191653.28927@phri.nyu.edu>
Organization: Utah State University
Lines: 29

In article <1991Apr5.191653.28927@phri.nyu.edu>, roy@alanine.phri.nyu.edu (Roy Smith) writes:
> 	Today, I was trying to boot a new FastPath (for those not familiar,
> a FastPath is an AppleTalk-Ethernet bridge/router/protocol-converter/etc).
> Anyway, it appeared that being connected to the ether while being
> configured via the AppleTalk side was confusing it, so I decided to unplug
> it from the (thin) ethernet segment it was on until I had it set up
> properly.
> 
> 	Making sure I didn't disrupt the ether segment was easy, I just
> took off the base of the T-connector.  But then I was left with an
> unterminated BNC on the FastPath.  The "right" way to terminate it, I
> suppose, would have been to get another T and put a thin terminator on each
> leg, but I didn't have any more terminators handy.  What I did instead was
> to just take a 1/8th Watt 51-ohm resistor and connect it across the center
> and shield contacts right on the BNC jack.  Shouldn't that have been all I
> needed?  The box kept complaining about ethernet errors, so it would appear
> it wasn't, but I don't understand why.  Can somebody enlighten me?
> --
> Roy Smith, Public Health Research Institute
> 455 First Avenue, New York, NY 10016
> roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
> "Arcane?  Did you say arcane?  It wouldn't be Unix if it wasn't arcane!"
----------------
Roy,
	I know this will sound simple but...
	A transmitter attached to a Tee connector on the coax sees the
impedance of the coax divided by two: two pieces of coax in parallel. So
you need a 25 Ohm load directly on the BNC connector of the FastPath box.
	Joe D.