telecom@ucbvax.ARPA (04/30/85)
From: Jon Solomon (the Moderator) <Telecom-Request@BBNCCA>
TELECOM Digest Mon, 29 Apr 85 23:58:21 EDT Volume 4 : Issue 185
Today's Topics:
Re: Surge Protectors
Re: Conferencing two lines
LD directory assistance charges (AT&T)
lightning protection for phone lines
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From: Ed Hall <edhall@rand-unix>
Date: 28 Apr 85 15:23:29 PDT (Sun)
To: TELECOM@bbncca
Cc: edhall@rand-unix
Subject: Re: Surge Protectors
I once (1966) lived in an older house which had carbon-arc surge
protectors across the phone lines. These devices consisted of a a flat
piece of carbon next to a U-shaped piece of ceramic with a smaller
carbon cemented into it. A small gap existed between the carbons, since
the second carbon was just slightly recessed into the ceramic. The
whole thing was sandwiched in a spring-loaded holder with several of
these protecters, connecting across the line and to ground.
The idea was that a surge of >150 volts or so would start a low-
impedance carbon arc. If the arc continued long enough, the cement in
the ceramic holder would melt and bring the carbons into contact,
forming a short.
These devices worked: we had a fair number of summer thunderstorms (this
was in Northern Ohio), and once after some particularly close lightning
strikes the phones stopped working. As it turned out, one of the
protectors had shorted--the carbons were pitted and the cement had
melted. But the phones were OK.
I've often wondered if a metal-oxide varistor or other ``newer
technology'' would have withstood this sort of surge. With most phone
lines now underground, the opportunities for induced currents from
lightning are a lot less than they were then, so it might not make much
difference.
-Ed Hall
edhall@rand-unix
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To: Ole Jorgen Jacobsen <OLE@sri-nic.arpa>
Subject: Re: Conferencing two lines
Date: 28 Apr 85 15:39:58 PDT (Sun)
From: Einar Stefferud <stef@uci-icsa>
If you don't want to build your own, you can buy a nice little two line
with hold (with lights) and two line conference and redial last number
for around $50 or sometimes less. It is the TeleConcepts Two Line
phone. Available a in various discount stores that I have seen. I
have three of them (two regular desk and one "dial-in-hand-set), and I
like them both.
I am not a stock holder. Don't have any idea where they come from.
Cheers - Stef
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Date: 29 Apr 1985 12:05:32-EDT
From: prindle@NADC
To: TELECOM@BBNCCA
Subject: LD directory assistance charges (AT&T)
I live in the 215 (Philadelphia area) area code and made a directory assistance
call to 609 (South Jersey) to get an Atlantic City number, and then placed the
call to the actual number. The actual call naturally appeared on my AT&T
portion of the bill. But the killer, is that the directory assistance call,
supposedly one of an allotment of 2 free DA calls via AT&T, came up as a $.50
charge on the Bell of PA portion of the bill! Apparently, Bell of PA owns a
special exception to the inter-state rules and handles calls to 3 neighboring
NJ counties. Since directory assistance is probably handled out of Trenton,
my DA call got handled and billed by Bell of PA. You won't believe how AT&T
handles this situation - you have to call them up (1-800-222-0300) and they
look you up to make sure you made the equivalent required call, then credit
your AT&T account! Since this is a totally manual operation, and since we
the public have never been told of this strange hack, chances are good that
Bell of Pa. is collecting gobs of half dollars which their customers really
do not owe; furthermore, when a watchful customer does go through the requisite
manual process, it seems as if Bell of Pa. ends up with AT&T's money. AT&T
also seems to be able to see the Bell of Pa portion of the bill on *their*
computer terminals. Why do I get the impression that AT&T is not as severed
from the operating companies as they would have us believe? hmmmm.....
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Date: Mon, 29 Apr 85 22:58:36 edt
From: ulysses!smb@Berkeley (Steven Bellovin)
To: telecom@bbncca.ARPA
Subject: lightning protection for phone lines
I wouldn't be that sanguine about modems being immune to lightning hits.
About 10 years ago, we lost not only a Bell data set (one of the old-style
clunkers), but the terminal attached to it. It might be that we had
unusually severe storms there (Chapel Hill, North Carolina); at other times,
I had a TV set's RF input section get fried when the CATV line took a hit
(the balun also blew), a light bulb burn out, and a circuit breaker trip.
Even optoisolators can be blown by that sort of overvoltage; you may find
it more convenient to unplug (and replace/repair) a burned-out surge protector
than to do without your modem for a while.
--Steve Bellovin
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End of TELECOM Digest
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