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From: pat@hprnd.rose.hp.com (Pat Thaler)
Newsgroups: comp.dcom.lans
Subject: Re: 10baseT Installation costs
Message-ID: <2230146@hprnd.rose.hp.com>
Date: 11 Apr 91 17:20:57 GMT
References: <5438@durin.sparta.COM>
Organization: HP Roseville Networks Division
Lines: 24

In comp.dcom.lans, jbreeden@netcom.COM (John Breeden) writes:

    RJ45s are used because the original concept of 10baseT was to use the exist-
    ing TELEPHONE wiring - and there's been a TELEPHONE wiring standard in use
    for years now .... AT&T's PDS (Premise Distribution System).

I award John Breeden the prize for the most accurate explanation of why
10BASE-T used the 8-pin jack (at least of those replies that reached
my system by today).  The use of the 8 pin jack in PDS and other office
wiring systems was a major factor in the decision.  It was also in use
in the 1BASE5 (StarLAN) standard and in ISDN (which specifies pinouts
for both 6 and 8 pin).  

On other points:  Link Integrity Test is a mandatory part of the 10BASE-T
standard and does not require additional wires.  SQE Test occurs between
the MAU and its local DTE and does not involve the twisted pair
wire.

Some vendors of 10BASE-T cards provide a connector on the card with the
pairs from pins 4 & 5 and 7 & 8 wired to it so that a phone may be
attached to the card without a separate splitter.  In other words, some
cards provide a built-in splitter.

Pat Thaler