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From: mikea@chinet.chi.il.us (Mike Andrews)
Newsgroups: comp.dcom.modems
Subject: Re: Which is better to have?
Message-ID: <1991Apr28.151528.19837@chinet.chi.il.us>
Date: 28 Apr 91 15:15:28 GMT
References: <3921.2812b277@hayes.uucp> <1991Apr23.001558.5462@dexter.mi.org> <1991Apr25.164452.1129@bilver.uucp>
Organization: Chinet - Chicago Public Access UNIX
Lines: 70

In article <1991Apr25.164452.1129@bilver.uucp> bill@bilver.uucp (Bill Vermillion) writes:
>In article <1991Apr23.001558.5462@dexter.mi.org> jsr@dexter.mi.org (Jay S. Rouman) writes:
>>In article <3921.2812b277@hayes.uucp> tnixon@hayes.uucp writes:
>>>unpredictable and dangerous.  I've seen several cases of lighting 
>>>going THROUGH an external modem, arcing all around inside, and into 
>>>the computer through the EIA-232 cable, so I can't list "lighting 
>>>protection" as an advantage of external modems.  It may help a
>>>little, but it's no guarantee.  You need external protection,
>>>whether your modem is internal or external. 
> 
>>Just the kind of reassuring words we wanted to hear during lightning
>>season. ;-)  What's considered good external protection these days?
>>Will MOV's across the line do the job?  There are tons of places
>>selling phone line protection devices but you never know what's inside
>>or if they have much chance of working.
>
>First thing to do is make sure your incoming lines are protected.
>Locally United has been using gas-discharge tubes for years.
>So.Bell started later - probably after seeing the lower failure
>rates for equipment in United.
>
>Before these were available we were buying them locally and
>installing them ourselves.
>
>When I was having lighting damage to such things as phone answering
>devices a few years ago, I had telco replace the carbon blocks on
>in-coming line with gas discharge - and it cured that problem.

You can order gas discharge tubes that thread right in to
replace the carbons on the protector on your phone lines
(where the phone lines enter the house).  Check that the ground
used by the phone company is a good one, not loose or connected
to a rusty electrical conduit.

The gas discharge tube replacements are avavailable from North Supply
in Lenexa, Kansas.

It's better if you can get your local telco to install gas-discharge
tubes for you since you're not supposed to mess with that side of
your phone service.

>Local hits however may get through everything.
>
>(TEXT DELETED)
>
>But gas discharge tubes seem to be a good start.

>(TEXT DELETED)
>
>And make sure your grounds are good.

Great advice!!
Ground your surge suppressors to a SOLID #10 A.W.G. wire with a
good connection to a copper cold water pipe or ground stake. 
Lightning travels on the surface of the wire due to its high
frequency, so the larger the diameter of the wire, the better.
Don't depend on the grounds in the electrical system or conduits.

To test for a good ground reference use an Ohmmeter (VOM).  Test
the resistance between two proposed ground points. When you find two
with less than a few Ohms of resistance between them, you've found
good grounds.

In a previous life I worked in the security system business.  The early
microprocessor-based control panels often died in less than a year in
our Midwest installations.  The makers on the west coast hadn't discovered
lightning yet.  Often these panels had a phone line connection less than
an inch from a power connection.  Now all of the makers have a terminal
on the panel marked "Earth Ground" connection along with detailed 
instructions on just what that means.