berger@clio.las.uiuc.edu (08/03/87)
Don't let the lightning protectors give you a false sense of security.
First, they offer no protection whatsoever unless connected to a proper
ground... and plugging them into a three-prong outlet is not adequate.
Even under the best conditions, they give limited protection. And you
can still get lightning damage via the rs232 connection. Lightning
doesn't always take the most direct path.
Mike Berger
Center for Advanced Study
University of Illinois
berger@clio.las.uiuc.edu
{ihnp4 | convex | pur-ee}!uiucuxc!clio!bergeradamsd@pnet01.CTS.COM (Adams Douglas) (08/04/87)
The last big thunderstorm we had in L.A. ('bout two months ago) was a _doozy_.
I took the precaution of unplugging all my computer equipment and removing the
cords from the cabinet connectors where I could. Although there were no direct
hits near my place, I know of at least one person who lost their disk-drive,
monitor, and modem, _despite_ their surge protector. Apparently the bolt hit
the power pole and propagated to ground through his house's wiring.
Ouch!mc68020@gilsys.UUCP (Thomas J Keller) (08/07/87)
I have limited this reply to comp.dcom.modems:
I had a Racal/Vadic 345[12] modem some time ago which used to eat the RS232
receivers in my terminal under certain circumstances! (seriously)
If I wandered away from the terminal while logged into a remote system, and
for any reason my line was dropped, if I didn't return before that GAWDAWFUL
sound the LOC uses to tell you you're off hook happened, my RS232 receivers
would be fried. Only explanation I could come up with was that somehow, the
mish-mash of over-driven tones was misleading the modem into some strange
output which fried my receivers. I replaced the receivers 7 times before I
finally got rid of that &^$%*&^%*%^ modem! Never had a problem since...
--
Tom Keller
VOICE : + 1 707 575 9493
UUCP : {ihnp4,ames,qantel,sun,amdahl,lll-crg,pyramid}!ptsfa!gilsys!mc68020
BITNET : ptsfa!gilsys!mc68020@ames.arpa <--- is this legal & correct?davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr) (08/20/87)
Lightning strikes can enter a computer either from the power line, modem
lines, or the roof. The first two can be isolated easily if not
cheaply. To isolate a power line fully, a motor-generator (MG) set is
used, mechanically coupled by a large non-conducting flywheel. This
protects against almost any line problems, but not against problems in
the generator itself (we found this out the hard way).
There is (was?) a device made to isolate RS232 connections, which is
based on having a large gap bridged by bidirectional optical link. I had
one of these which used two LEDs and two photodiodes. There is better
technology today, but the old stuff worked.
Your computers can be as safe as you can afford to make them. For many
systems the risk doesn't justify the cost of protection.
--
bill davidsen (wedu@ge-crd.arpa)
{chinet | philabs | seismo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -mechris@mimsy.UUCP (Chris Torek) (08/21/87)
In article <747@uhccux.UUCP> bob@uhccux.UUCP (Bob Cunningham) writes: >Some postscript notes on the 1985 lightning strike here at the U. of Hawaii. ... >On the other hand, we're much more thoroughly ethernetted on campus >now and I don't have any experience with lightning zapping ethernets. >One hopes that the transceivers are the weak links. We get quite a few near-miss strikes here every summer; the power goes out, the air conditioning quits, the machines break ... and now the Ethernet transceivers get zapped. Apparently they are indeed the weak links. We have one interbuilding cable; each summer we lose several transceivers in one or both buildings. In two years, we have not yet had any Ethernet boards quit immediately after a thunderstorm. I think the count of dead transceivers is well into the tens, though. -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690) Domain: chris@mimsy.umd.edu Path: seismo!mimsy!chris
phil@amdcad.AMD.COM (Phil Ngai) (08/21/87)
In article <8057@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes: >the weak links. We have one interbuilding cable; each summer we >lose several transceivers in one or both buildings. Which is why all the interbuilding links I put in were fiber. Using coax between buildings is asking for trouble. -- I speak for myself, not the company. Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.com