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Path: utzoo!linus!decvax!harpo!seismo!hao!hplabs!sri-unix!w8sdz@brl
From: w8sdz@brl@sri-unix.UUCP
Newsgroups: net.micro
Subject: Re:  Some modems dont work on some lines
Message-ID: <3609@sri-arpa.UUCP>
Date: Fri, 29-Jul-83 12:23:58 EDT
Article-I.D.: sri-arpa.3609
Posted: Fri Jul 29 12:23:58 1983
Date-Received: Mon, 1-Aug-83 09:39:00 EDT
Lines: 12

From:      Keith Petersen 

Make sure that only "tip" and "ring" are connected at the modular plug.
(that's usually red and green wires).  If the other two (usually unused)
black and yellow wires are connected, some modems will refuse to
operate.  Because of this, some manufacturers of modems are suppling a
modular "Y" connector that only supports tip and ring connections to the
modem.  In a commercial multi-line telephone the yellow and black wires
are used for what's called the "A Lead", which is a circuit that
connects to auxilary hook-switch contacts in your telephone.  This
circuit is used to cancel the "Hold" relay when you pick up the phone.
--Keith