Re: [TECH] Modem-to-Modem wire connection

From: Bob Goodwin (
Date: Sun Apr 23 2000 - 21:32:49 CEST

A telephone circuit doesn't care if the wires are reversed, the
only thing that changes is battery voltage polarity and that is
usually of no consequence with modern equipment. Years ago the
DTMF dialers were sensitive to this but eventually a diode bridge
was added to eliminate that problem.

I tried it and the ATE1 ATA and ATD commands seem to result in a
connection between the computers but I never transfered any data.
That remains for another time. But it looks like minicom will
connect them with a standard telephone cable with RJ connectors
on either end using those commands. I used different modems, a
USR and another using Rockwell chips with the data rate set to
19200 on both ends..

Usually the two center wires, red and green are one telephone
line, the two outside wires [on a four wire plug] are a second
line, usually black and yellow. It is a full duplex circuit T&R
on the same pair, nothing else should be required.

I am no expert on telephone circuits but I do know the above to
be true.

Bob Goodwin, Durant, Florida

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