Path: utzoo!utgpu!watserv1!watmath!att!att!bu.edu!buit13!kwe
From: kwe@buit13.bu.edu (Kent England)
Newsgroups: comp.dcom.lans
Subject: Re: Thin Ethernet signal loss @ connectors
Summary: thin is not cheaper
Message-ID: <66852@bu.edu.bu.edu>
Date: 23 Oct 90 18:32:06 GMT
References: <6464@bgsuvax.UUCP>
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In article <6464@bgsuvax.UUCP> jyoull@bgsuvax.UUCP (Jim Youll) writes:

>I hope this doesn't sound too dumb, but here goes...
>
	Dumb questions always welcome on this station.

>On a Thin Ethernet segment, is there significant signal loss at
>each "T" connector?
>
	Anytime you insert a connector in thin-net you get some loss
and reflection.  The spec tells you how many you can have on any given
185m segment (but I always forget the numbers and have to look it up).
Isn't it fifteen stations and 30 connections?

>What if the connector is not attached to an Ethernet card, but is
>just left unconnected?
>
	Not really any different.  The open side of the T is not
supposed to present a problem.  It is like powering down an attached
node.

>How about through the "barrel" BNC connectors used to join two pieces
>of thinnet coax in the absence of a "T" connector.
>
	Looks like a T.

>We are looking at options for prewiring a building. 10base-T is 
>preferred, but cost is a big problem and Thinnet is fast and cheap.
>I've been asked to find out about leaving ready-to-go connections in the
>walls with barrel
>connectors or T-connectors at each workstation, for extraction when
>needed.
>
>Suggstions invited. Thanks.

	Thin-net is no faster than 10BaseT, either in network speed or
speed of installation.

	Daisy-chaining thin-net thru your walls will end up costing
you much more than 10BaseT.  It is just that it is a different line
item in your "budget" called "labor".

	You cannot attach workstations to thin-net T connectors with
any length of patchcord.  The T must go onto the back of the PC.  If
you must daisy-chain thin-net thru walls I recommend the AMP solution,
but you won't like it because the cables and wall jacks are expensive.

	Here is a compromise.  If you have labs or classrooms to
network, link them up with thin-net daisy chains.  Then use an adaptor
like the Cabletron CT-100 to attach this small daisy-chain to a
10BaseT port.  Install isolated nodes directly onto 10BaseT.  This way
the thin cable is outside the walls and entirely within one room.
Easy to maintain and fix.

	If you take the low end 10BaseT concentrator gear, you should
be able to reach a target of about $100 per port now or in the near
future.  The workstations will come with 10BaseT already in place.
NeXT done it already.

	--Kent