Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site mcc-db.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!mcnc!philabs!cmcl2!seismo!ut-sally!mcc-db!paver From: paver@mcc-db.UUCP (Bob Paver) Newsgroups: net.micro.mac Subject: Re: Mac Modem Port Configuration Message-ID: <29@mcc-db.UUCP> Date: Thu, 3-Jan-85 23:48:13 EST Article-I.D.: mcc-db.29 Posted: Thu Jan 3 23:48:13 1985 Date-Received: Mon, 7-Jan-85 02:22:54 EST References: <4469@cbscc.UUCP> Organization: MCC (Austin, TX) Lines: 42 Here's the pin layout for the modem port on the Mac. This description is from Cary Lu's book. 1 Cold ground 2 +5 volts 3 Cold ground 4 Transmitted data + 5 Transmitted data - 6 Filtered +12 volts 7 Handshake for printer or carrier detect; also for external clock in synchronous communication. 8 Received data + 9 Received data - Although power is available on lines 2 and 6, any connecting devices should not depend on the power; the available current is small and the power is not guaranteed in future designs. I used the following pins in the cable that I use to connect my Mac to a US Robotics Auto Dial 212A modem. Note that pin 5 on the RS-232C side is simply jumpered to pin 20. This hold DTR high. If I don't do this, my modem drops carrier almost instantly. By the way, I don't pretend to understand any of this. RS-422 RS-232C Mac DB-9 Modem DB-25 5 2 9 3 5 -+ 1 7 | jumper 7 20 -+ Good luck. --------------- Bob Paver MCC Austin, TX paver@mcc.arpa