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Path: utzoo!linus!decvax!tektronix!uw-beaver!cornell!vax135!houxz!houxm!mhuxl!ulysses!gamma!mb2c!uofm-cv!cosivax!dbo
From: dbo@cosivax.UUCP
Newsgroups: fa.info-mac
Subject: Re: modem pin connections
Message-ID: <160@cosivax.UUCP>
Date: Tue, 24-Jul-84 12:39:02 EDT
Article-I.D.: cosivax.160
Posted: Tue Jul 24 12:39:02 1984
Date-Received: Fri, 27-Jul-84 02:17:57 EDT
References: <1280@uw-beaver>
Organization: COSI, Ann Arbor, MI
Lines: 36

The modem signals as published in ST.mac (May 1984) are as follows:

	MAC		APPLE MODEM
1. frame ground		nc
2. +5v			data set ready
3. signal ground	signal ground
4. transmit data +	not connected
5. transmit data -	receive data 
6. +12v			data terminal ready
7. input (HSC)		carrier detect
8. receive data +	frame ground
9. receive data -	transmit data

The connections they suggest are:

3.	       <->	      3.
5.	       ->	      9.
6.	       ->	      6.
7.	       <-	      7.
9.	       <-	      5.

I have had success connecting my U.S. Robotics modem using the
following scheme:

MAC (db9)		   ROBOTICS (db25)
3.	       ->	      7.  (signal ground)
5.	       ->	      2.  (transmit data)
7.	       <-	      8.  (carrier detect)
9.	       <-	      3.  (receive data)

I didn't bother to run a high signal from MAC 6. to data terminal ready 
(ROBOTICS 20) because the modem doesn't seem to need it and I don't
really care if the modem hangs up when I turn my terminal off (also, I
had some 4 wire cable handy, so it was just more convenient).

This setup works fine for a Mac running MacTerminal.