Path: utzoo!attcan!uunet!lll-winken!ames!pasteur!ucbvax!NIEHS.BITNET!ALBRO
From: ALBRO@NIEHS.BITNET
Newsgroups: comp.sys.apple
Subject: RE: Re: Null modem file transfer.
Message-ID: <8901132128.aa01422@SMOKE.BRL.MIL>
Date: 12 Jan 89 20:13:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 9

This is for (aash@ms.uky.edu) in regard to using a printer cable for a modem.  N
No, it won't work.  The problem is RS232 pin 20, which needs to go to port pin
1, but doesn't in the printer cable.  This is called "handshake out" by Apple,
DTR by everyone else.  In the printer cable, this pin (at the port) is
connected to DSR/DCD or not connected at all.  In the printer cable, RS232
pin 20 (DTR) is connected to port pin 2 (handshake in), so the modem and
printer cables are reversed.  The printer cable will act like a "null modem"
since it also reverses the signal in/out leads, and if your serial port
ignores DTR and DSR you can use it that way.