Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!ccu.umanitoba.ca!kujanpa
From: kujanpa@ccu.umanitoba.ca
Newsgroups: sci.electronics
Subject: Converting RS-422 to RS-232
Message-ID: <1990Dec10.173757.1162@ccu.umanitoba.ca>
Date: 10 Dec 90 17:37:57 GMT
Sender: kujanpa@ccu.umanitoba.ca
Distribution: na
Organization: University of Manitoba, Winnipeg, Canada
Lines: 34


Hi everyone.  Here's my problem:
 
Besides our ethernet, we have a packet
switching network (Develnet).  This network
provides 9600 baud ASCII serial ports to the
mainframe for pc users.

The problem comes when we connect a Mac to
one of these ports.  They will occasionally
lockup to a point, where a linecard has to be
pulled and reset.

I think the problem comes from the Mac (RS-422?)
talking to RS-232.  All we use is a modified cable
to emulate RS-232.  Over long distances the voltage
level coming out of the Mac is very small (ie. not
valid data).

The question: 

Can I build a circuit to change from RS-422 to RS-232?
Can this circuit be powered from the Mac SE port?
Using an external power supply is ok, but if the    
circuit could be powered from the line it would be
great.

Any suggestions, ideas, etc. are more than welcome!
Thanks in advance!
Bob Kujanpaa
kujanpa@ccu.UManitoba.CA


Any suggestion