Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!mcvax!fmr
From: fmr@cwi.nl (Frank Rahmani)
Newsgroups: comp.dcom.lans
Subject: Re: Re: Simple thin ethernet question
Message-ID: <986@sering.cwi.nl>
Date: 31 Jul 89 19:58:21 GMT
References: <13200001@net4>
Organization: CWI, Amsterdam
Lines: 68

> Nf-From: net4.UUCP!tawab    Jul 28 09:38:00 1989
> /* ---------- "Simple thin ethernet question" ---------- */
> Hi, Kenneth Herron
> 	>Hello,
> 	>My question is quite simple:  all the docs we have on installing the
> 	>cables show both halves of the cable running right up to the back of the
> 	>computer, and the T connector attaching directly to the network card
> 	>in the PC.  Does it HAVE to be this way?  Can we keep the main cable 
> 	>and the T in the wall and run a short piece of cable to the network card?
> 	>How long can this stub piece be?  Assuming we can't do this,
> 	>any suggestions for doing this wiring aesthetically?
> First I tried to mail but it bounced, where are you, in UK, US, ???
> We have a Yellow Cable Ethernet, but I guess there are just some differences
> in the lenght of the Cable. I can't belive the you are conecting the "T"
> (I guess "T" == Tranciever ?)
...dumped nice network pictures...
Sorry, wrong guess.The 'yellow cable' is definitely 'thick ethernet' and as
such your description are correct, but only for that kind of network. The
question however was about 'thinwire ethernet', which is a 50 Ohms coax cable
about 6mm dia. The physical architecture is a little bit different from
thickwire installations.
Thickwire:
               ---------        ---------
               |transc.|        |transc.|
_______________|       |________|       |____________final resistor
yellow cable   |       |  y.c.  |       |   y.c.
               ---------        ---------
blue dropcable->   |        b.d.->  |
                   |__              |__
                 to your workstations ethernet port
Thinwire:
---------------| |---------------| ||<--final resistor
               | |               | ||
               | |               | |
               ---               ---
this is the T-  | connector (also | called BNC-T-connector in question
             -------           --------
             |     |           |      |
              your workstations
The T connector is just a three way connector with 2 male and 1 female (or
the other way around) outlets, just mechanical, no electronics involved.
According to the specs ,there is NO cable allowed between this T-piece and
the workstation(s). I have seen people reporting in this group having used
cables up to seven meters long without any problems. If you have a big
network ,especially many thinwire segments connected by bridges and/or
multiport boxes to thickwire backbone(s) this is a definite NO GO!
You will have lots of unexplainable errors. For the esthetic part, this is 
what we do:
1)use twin cables (just two thinwire cables glued together, don't mix up with
  the IBM twinwire network cables, which are coax cables with two inner condu-
  ctors).So only one cable leads up to your workstation.
2)use right-corner connectors between your cables and the T-piece. This will
  prevent you from getting two great bows in your cable.
                 |                             |
        this  |-----|       instead of  /-------------\
              \     /                  /               \
               \   /                  |                 |
                \ /                   |                 |
                 ||                   \                 /
Sorry this has gotten kind of long, but difficult to explain otherwise.
Regards
fmr@cwi.nl

-- 
It is better never to have been born. But who among us has such luck?
Maintainer's Motto:
	If we can't fix it, it ain't broke.
These opinions are solely mine and in no way reflect those of my employer.