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From: dmt@ahuta.UUCP (d.tutelman)
Newsgroups: net.micro.pc
Subject: Re: Homemade AT Serial Port/RS232 Cable - (nf)
Message-ID: <361@ahuta.UUCP>
Date: Tue, 15-Jan-85 07:51:46 EST
Article-I.D.: ahuta.361
Posted: Tue Jan 15 07:51:46 1985
Date-Received: Wed, 16-Jan-85 05:24:39 EST
References: <816@pucc-i>
Organization: AT&T Information Systems Labs, Holmdel NJ
Lines: 23

REFERENCES:  <816@pucc-i>

Thanks for posting the pin assignments. I'd like to make one small
correction, not in the pins but the terminology.  A "null modem cable"
is NOT a modem cable without control leads.  It's a cable that
REPLACES a modem, so that two back-to-back terminals (or terminal
and computer) can converse without benefit of a modem.

For example:

Transmit data	------------------------------	Receive data
Receive data	------------------------------	Transmit data
Request to send	------------------------------	Clear to send
Clear to send	------------------------------ 	Request to send
Modem ready	------------------------------	Terminal ready
Terminal ready	------------------------------	Modem ready
Ground		------------------------------	Ground

is an example of a null modem with some control leads implemented.
Note the transposition of leads (Transmit to Receive & vice-versa)
that is the characteristic of null modems.

				Dave Tutelman