swc@cbscc.UUCP (Scott W. Collins) (12/27/84)
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Sorry if I am bringing up an old issue, but can someone
send me the 9-pin D-connector layout for the modem port
on the back of the Mac? Please, remember to specify
what point-of-view the description is from if pin numbers
aren't evident.
Please mail directly as I'd like to prevent unnecessary
net work (get it?). Other interested parties may mail
to me for the info and I will pass along the layout
(with credit to the source).
Thanks, fellow Mac-ers.
Scott W. Collins
ATT - Bare Rubber Trees
Columbus, OH
{ihnp4|cbosgd|..}!cbscc!swcpaver@mcc-db.UUCP (Bob Paver) (01/04/85)
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