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From: andrew@jhereg.osa.com (Andrew C. Esh)
Newsgroups: comp.dcom.lans
Subject: Re: another 10BaseT wiring question
Message-ID: <1991Apr15.213830.9317@jhereg.osa.com>
Date: 15 Apr 91 21:38:30 GMT
References: <9736@mentor.cc.purdue.edu> <1991Apr10.035307.29375@netcom.COM> <1991Apr10.172500.24529@ux1.cso.uiuc.edu>
Organization: Open Systems Architects, Inc., Mpls, MN
Lines: 49

I would rather avoid 50-pin stuff too. I have seen wiring closets where
they have gone wild with these things, and have introduced a lot of EMI
after all the cross connections. One place went from 8-pin ports to a
harmonica, 50-pin from the harmonica to an 8-pin port patch panel (incase
they wanted to re-assign ports) RJ45 (oops, I mean ISO 8877) straight
through jumpers to ANOTHER RJ45 panel, yet another 50-pin to 66 blocks, and
from there to the other IDFs to be punched through yet another panel. By
the time they got done there was so much EMI ingress the whole thing didn't
work. I think they got too prissy-neat-and-clean when they planned their
wiring. What's wrong with a mass of RJ45s going stright from hub to the
wall? I do it in my machine room. It works.

That leads me to my second pet peeve. If one wire becomes faulty in a 50-pin
jumper, the whole thing needs to be replaced. The other way, you just need
to replace the jumper for one port, and you can easily crimp that togeter
yourself. I keep a spool of wire, a crimper, and some 8-pin connectors in
the machine room just in case I feel the need. You never know when you
might need to patch something together. You need the spool anyway - if
someone's UTP in the wall is shot, you can temporarily run their port into
the next office and grab a spare off that guy's wallplate.

If you really need 50-pin, as is the case with the David 10baseT cards, try
calling David. I would be surprised if they don't supply the jumper as an
accessory to the card. I have a David in for eval at the moment, and a
50-pin jumper, along with a harmonica sort-of-thing came with it. Nowhere
does it say David on it, so it may be third party, but it works.

The thing to watch out for is the pinouts. I tried to use a Xyplex
10baseT harmonica and 50-pin for connection to a Terminal Server card in a
Xyplex Communications server. The ports wound up with the pins from port 1
(10BaseT) spread out as pin 1 on each of the first four serial ports, or
something akin to that. You'd think they would pin out their cards so the
same 50-pin jumper and harmonica combination would work for both of them.
Ho hum. Anyway, you should be able to get 12 ports (12*4=48) out of the 50
pin jumper, and be sure to check the pinouts so the ports, as distributed
on the 50 pin connector, each actually wind up in the right port in the
harmonica, in the right order, obviously.

"Let's go punchin' down,
 Everybody's learnin how,
 Come and cable networks with me"

 (apologies to the BeachBoys,
	"Fun, Fun, Fun, 'til her Daddy took the T-bird away")
-- 
Andrew C. Esh			andrew@osa.com
Open Systems Architects, Inc.
Mpls, MN 55416-1528		Punch down, turn around, do a little crimpin'
(612) 525-0000			Punch down, turn around, plug it in and go ...