Subject: RS232 <=> RS422 - test-drb@ccmp.vtda.org

27 Jun 2006

...
 >A lot of RS422 equipment uses TTL level to create
the +/- signal lines
>- hooking it directly to RS232 may blow up your tranceivers, not work,
>or both.  Or, it may work - I think old Macs were tolerant enough to
>do that. 
...
 Yes, Macs with RS-422 ports usually could take RS-232
(using a converter
cable) without a problem. I did this all the time. 

 SGI Indy/Indigo2 era machines have mini-DIN 8 serial ports that would do either depending
on which device file you used, Sun machines (SS5 and U1, haven't poked around
in my Ultra 10 that much yet) had jumper-selectable RS232 or 422. I think DEC423 was very
close to RS422, and there are few conversion problems there (reduced max cable
length, I think).