Preventing serial cable interference

[Michael D. Crawford]

We have a great deal of trouble here with our Sun serial ports either hanging up
(meaning rebooting fixes them) or being blown (meaning we need to replace the
board).

Sun Service says it is from our long serial cables being left unplugged at the
far end, or being plugged into powered-off equipment, which causes the 
unterminated cables to pick up interference and generate lots of
interrupts.  I do use the Sun perfmeter program to monitor interrupts, and
sometimes see the rate jump from a few hundred per second to tens of
thousands, which is cured by unplugging the cable at my end; however, this
behavior is not always observed before ports go out.

My users have not complied to well with my requests to leave their cables
plugged into turned on devices, understandable since most of them are used
to download into equipment with noisy fans.  

What I would like to know is if there is some kind of isolator I could make
or buy that would overcome this problem, at least some kind of terminator
I could plug in the other end of the cables when they are not being used.

I would greatly appreciate helpful suggestions of any sort, as Sun does not
seem to know anything better to tell me.

Thanks in advance,

-- 
Michael David Crawford			Consulting for:
Oddball Enterprises			Octel Communications Corp
694 Nobel Drive				890 Tasman Drive
Santa Cruz, CA 95060			Milpitas CA 95035
pyramid!vsi1,!octel!mike
CI$ 72377,623