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From: howard@cos.com (Howard C. Berkowitz)
Newsgroups: comp.dcom.lans
Subject: Re: Lattisnet/Ethernet over Twisted Pai
Summary: Continuity vs. pair sense
Keywords: Ethernet, LattisNet, 802.3, Synoptics
Message-ID: <15364@cos.com>
Date: 21 Feb 89 12:46:34 GMT
References: <98@cs.columbia.edu> <114400001@uxa.cso.uiuc.edu> <1689@umbc3.UMBC.EDU>
Organization: Corporation for Open Systems, McLean, VA
Lines: 45

In article <1689@umbc3.UMBC.EDU>, digennar@umbc3.UMBC.EDU (Mr. Jerry DiGennaro) writes:
> 
> The firm I work for has two and ahalf buildings running LattisNet at
> this time....
> .  The only major problems has been with the initial
> wiring.  Phone people think any four wires will make a four wire
> circuit.  LattisNet needs a continous twisted pair for the receiving
> side and a continous twisted pair for the transmit side.  Continous
> means from the back of the PC/computer/host all the way back to the
> LattisNet concentrator. 


I wonder if you could clarify if your problems with paired wire
are due to a loss of pair sense, or are you saying that you have had
problems with wire closet punchdowns?

In a pair sense problem, some interpretation of installation practice
causes two wires which start out in one pair to be assigned to two
different pairs.  For example, there is a nonobvious point in 
DECconnect async jack installation instructions, which has a good
reason in a pure DEC environment (essentially avoiding the need for
a separate null modem with DECservers), which will cause certain
"paired" wires at the office wall jack not to appear in the same pair
in the wire closet. When this jack was reused for Wangnet (through
a dual-coax-to-twisted-pair balun), it simply didn't work, although
it did when rewiring was done to keep all pair wires together.  

In the case above, the twisted pairs, in the eventually working condition,
went through 2-3 wire closets containing 66-type punchdowns and/or
RJ45 patch panels.  As long as the pairs were kept together, everything
worked.

In the original comment about Lattisnet, would the above wiring closet
arrangement be a problem, assuming punchdowns, etc., are done properly?
Well-installed punchdowns should seem like the twisted pair, but
Murphy doesn't always allow that!  Does Lattisnet really need a continuous
wire which does not go through wire closets (with the caveat that these
closets are wired by competent data installers as opposed to general
voice people)?

-- 
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