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Path: utzoo!watmath!clyde!cbatt!gatech!lll-lcc!unisoft!mtxinu!ed
From: ed@mtxinu.UUCP
Newsgroups: comp.dcom.modems,comp.periphs,misc.wanted
Subject: Re: Reliability of Modular Jacks
Message-ID: <299@mtxinu.UUCP>
Date: Tue, 10-Feb-87 01:10:16 EST
Article-I.D.: mtxinu.299
Posted: Tue Feb 10 01:10:16 1987
Date-Received: Wed, 11-Feb-87 05:54:25 EST
References: <267@aucs.UUCP>
Reply-To: ed@mtxinu.UUCP (Ed Gould)
Distribution: na
Organization: mt Xinu, Berkeley, CA
Lines: 34
Xref: watmath comp.dcom.modems:195 comp.periphs:193 misc.wanted:501

>Most of the terminals on our campus are presently connected to the wall
>with four-prong plugs. We are considering wiring new terminals with
>either four-wire or six-wire modular jacks. If anyone has had bad
>experiences with these connectors I'd appreciate hearing your warnings.
>In particular are these connectors any more sensitive to noise than
>what we have been using.

We've been using modular hardware for terminals for a few years, with
no ill effects.  The modular gear shouldn't be any more noise-prone
than other connectors.

I offer two cautions, however.  First, modular connectors are not very
robust mechanically - they don't stand up well to repeated
insertion/removal cycles.  Second, there is no standard way in which
they're wired, so care in desigining the system is needed.  In
particular, be careful of polarity reversals: standard
modular-to-modular cables put a half twist in each pair.  Also, the
connections are paired from the middle out, so that 4- and 6-wire
systems can be made compatible:

	----- 6wire -----
	   -- 4wire --

	C1 B1 A1 A2 B2 C2

I recommend using a standard cabling model, and building the connectors
at the modular-to-DB25 end in two or three different ways to make the
connections work the way you want.

-- 
Ed Gould                    mt Xinu, 2560 Ninth St., Berkeley, CA  94710  USA
{ucbvax,decvax}!mtxinu!ed   +1 415 644 0146

"A man of quality is not threatened by a woman of equality."