surge protectors

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2 total messages Started by Daniel R. Grayson Mon, 31 Aug 1992 22:04

#513

Author: Daniel R. Grayson
Date: Mon, 31 Aug 1992 22:04

10 lines
964 bytes

Could someone please fill me in on the current wisdom about how to protect
long RS-232 lines from lightning?  The surge protectors in the catalogs cost
about $60 each, and who knows if they work?  We have many unshielded lines
travelling throughout a couple of old buildings, with PCs and ascii terminals
connecting to a terminal server.  Are there surge protectors that protect 16
lines at a time?  How do we build one ourselves?

What about for ethernet lines, too?

Is this the right group for this?

Re: surge protectors

#541

Author: Daniel R. Grayson
Date: Sat, 05 Sep 1992 01:44

16 lines
1516 bytes

The best surge/lightning protector I've found for RS-232 lines seems to be
one from Black Box - I don't know the name of the manufacturer.  It costs
$425, and will protect 32 conductors.  Connections are via a simple terminal
strip.  The protection consists of avalanche diodes with a breakdown voltage
of 25V back-to-back between each line and ground, with a gas tube also
between each line and ground.  As I gather it, the theory is that the diodes
switch on quickly, but can't dissipate much power, whereas the gas tubes
conduct electricity easily once the gas is ionized, thereby protecting the
diodes and the equipment.  I suppose the diodes alone just wouldn't be
adequate, because they may be destroyed by a lengthy surge (lightning).

Can anyone vouch for the theoretical effectiveness of this method?  Can
anyone vouch for whether the particular design of this box is correct?  (I
don't know any values for the gas tube, so I'm asking here for someone with
experience with this product or something similar.)  Should we spend out
money on this?

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