Path: utzoo!attcan!uunet!mailrus!shadooby!samsung!cs.utexas.edu!rutgers!att!cbnewsj!jwi
From: jwi@cbnewsj.ATT.COM (Jim Winer @ AT&T, Middletown, NJ)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Modems and Telephone Lines
Summary: wire colors
Message-ID: <2400@cbnewsj.ATT.COM>
Date: 21 Nov 89 14:27:06 GMT
References: <13410@eerie.acsu.Buffalo.EDU> <1989Nov20.135228.2503@ug.cs.dal.ca>
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 53

In article <1989Nov20.135228.2503@ug.cs.dal.ca>, morrison@ug.cs.dal.ca (Brad Morrison) writes:
> For most phone lines there are four wires.  They are really two pairs of
> wires.  I believe it's Black & Red, and Green & Yellow.  Each pair is for
> a separate phone line.  So, you can carry up to two separate lines from
> each cable (this is for a regular modular residential jack.  I don't know
> if this applies to PBX systems or not).

	Red = tip
	Green = ring

tip + ring = normal telephone circuit

	yellow = ground
	black = auxilliary

grounding aux temporarily is used for signalling in old type key systems.

Also 3 pair setups for PBX or keysystems

	pair 1 = analog
	pair 2 = digital signaling
	pair 3 = power

or

	pair 1 = power
	pair 2 = receive analog
	pair 3 = transmit analog
	
or

	various other arrangements depending on manufacturer
	
Also 4 pair setups used for PBX or keysystems

	various arrangements depending on manufacturer
	
In short, if you want to know the signalling setup, you need the PBX
installation documentation.

WARNING: some PBX setups, especially those with separate transmit and
receive pairs cannot accept a standard modem. (If you can connect an
answering machine directly, you can usually connect a modem.)

Good Luck.

Jim Winer -- The opinions expressed here are not necessarily
	     and do not represent nor in any way imply
	     of any other sane person and especially not
	     employer.
"My reply is that such pre-theoretical conceptual essences are often
riddled with deep ambiguity and internal incoherence, despite strong
convictions people have that they know what they mean." -- Aaron Sloman