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From: bill@bilver.uucp (Bill Vermillion)
Newsgroups: comp.unix.sysv386
Subject: Telco Lightning protect.  Was Re: internal Telebit
Message-ID: <1991Jan6.164011.23399@bilver.uucp>
Date: 6 Jan 91 16:40:11 GMT
References: <130@limbic.ssdl.com-> <5626@rsiatl.Dixie.Com> <131@limbic.ssdl.com>
Organization: W. J. Vermillion - Winter Park, FL
Lines: 43

In article <131@limbic.ssdl.com-> gil@limbic.ssdl.com (Gil Kloepfer Jr.) writes:
 
->An interesting follow-up question is this:  There is a small amount of
->lightning protection on the phone lines (usually of the carbon spark-gap
->variety), which obviously don't eliminate the problem nearly enough
->for sensitive electronic equipment.  I also know (and have preached)
->that NOTHING can stop a good lightning strike from frying your computer,
->except for unplugging it from the power and phone lines.  However, how
->effective are a pair of MOV's from each leg of the phone line to ground?
->(ie. ring-to-ground and tip-to-ground).  One problem with both the voice
->power board (no MOVs) and the modem (only a MOV across ring and tip) was
->the lack of adaquate means of sending the offending high-voltage surge
->to ground.  After having my unfortunate experience, I made a little
->phone-line surge suppressor as mentioned above...however I'm not too
->sure of how effective it may be.  BTW: my device handles 4 phone lines,
->and it is connected at the first available place I can attach it to the
->phone line.

As all of us who live in Central to South Florida can attest, lightning is
a daily fact of life here. When I first started getting into direct connect
modems (not internal) about 10-11 years ago, many of the modem users were
installing an extra device at the incoming line that included gas-discharge
tube.   Locally we had three phone companies, General, Bell and United
(talk about a mess getting things working between all three!).

United (in those days Winter Park Telephone) was installing gas-discharge
as a matter of course in ALL their installations.  They found it cut down
on their repairs considerably.  Bell (now BellSouth) was still installing
carbon-blocks.  Those were the ones the comuters users were adding
protection too.  Since that time I believe all local telcos are using
gas-discharge tubes.

The blocks, identical to the ones telco used, were about $10 to $12 each.
We were blowing answering machines at another site.   Called telco and had
gas-discharge put in place of the carbon blocks and we didn't have any more
problems.  (Could be we never had any more lightning hits, but the troubles
ceased when the tubes were installed).



-- 
Bill Vermillion - UUCP: uunet!tarpit!bilver!bill
                      : bill@bilver.UUCP