A recent post mentioned running RS422 full-duplex with a 5-wire cable.
Is the 5th line for ground?  I've assumed (uh oh!) one of the benefits of
RS422 and RS485 was the absence of a common ground running a couple
thousand feet (ground loops, noise, etc).

A friend working as a network consultant has a client who recently moved
into a new and much larger facility.  A PC communicates via RS232 to some
uP-based I/O boxes out in the warehouse (cable run was <50ft. now is
~150ft.).  The PC's serial port has blown several times since the move.
The PC and the remote I/O boxes are on separate breakers, but
the electrician says all is OK with AC service and grounding. Their plan
is to convert to RS485.  My serial comm experience has been with RS232,
so I can't offer anything beyond the MAXIM 485 data sheets, etc.
Has anyone dealt sucessfully with this symptom by replacing RS232 with
485?

John
______________________________________________________________________________

John Leonard, instrument technician                        Electron Hacker
College of Science & Engineering                           Bit Banger
Saginaw Valley State University                            Bassist
University Center, MI USA  48710                           Dad
_____________________________________________________________________________