SIMPKINS, Terry wrote:
>
> I've run them "a fer piece" over the years.
> HP says 50 ft for RS-232 (check's in the mail)
> It depends on lots of factors.  How fast are you running them?
> Is there hig voltage on the wire route?, etc.
> I would be suprised if you have any problems under 200 ft (if you keep the
> cables off
> of the light fixtures).
> Terry Simpkins
>  ----------

RS-422 has much better range the RS-232 as it uses a differential signal
to transmit data.  The idea here is that what is important is the
difference in voltage between the wires rather than a simple voltage
level in a single wire.  If you get interference with one of the wires
say +n volts then the other wire also sees the +n voltage and the
difference remains the same (a-b = (a+n)-(b+n))...

I recall a story about a VPLUS escalation in the early/mid eighties
where the customer was getting really funny behavior on one or a few
specific terminals.   A lot of time and effort was spent checking
software and hardware components but the problem wasn't nailed until
someone realized the the problem device(s) were next to the elevator
shaft -- Magnectic coupling with the motors would occur only when the
elevator was under heavy load... Try tracking that down.

I personally fielded another where they had routed the rs-232 cables
through the ceiling and around several flourescent light fixtures with,
predictible in hind sight, flakiness....

Jim