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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics,misc.legal
Subject: Re: Phone Harassment
Summary: Telephone line protection against excessive voltage and currents
Message-ID: <3667@kitty.UUCP>
Date: 18 Mar 90 04:13:57 GMT
References: <21849@watdragon.waterloo.edu> <13746@watcgl.waterloo.edu> <5336@mmsac.UUCP>
Distribution: na
Organization: Recognition Research Corp., Clarence, NY
Lines: 33

In article <5336@mmsac.UUCP>, jim@mmsac.UUCP (Jim Lips Earl) writes:
> > I saw an interesting method of getting back at phone harrassers
[description of nonsense method deleted]
> That sounds hokey to me.  
> ...
> Also, I know the phone company used to have "fuses" on each user's
> phone "pair".  So if you hooked, say, 120vac across your phone line,
> these fuses would blow, and you would be without service until the
> phone company replaces the fuses.

	Protection against excessive voltages and currents exists at both
the central office (CO) and subscriber end of telephone circuits.

	Each pair in any outside plant cable which enters a CO is terminated
in a circuit known as a "protector".  A CO protector generally contains two
elements: (1) an over-voltage device which conducts at between 500 to 600
volts and shorts the cable pair to ground; this element employs either an
air gap between two carbon blocks, or a discharge tube filled with inert gas;
(2) an over-current device, commonly called a "heat coil", which consists of
fusible wire which heats and opens at currents typically above 0.25 ampere.

	Each pair at a subscriber location terminates in a "protector block"
which provides the same degree of over-voltage protection described above
using either the carbon block method or discharge tube.  In addition, some
older protector blocks contain fuses, although this has not been standard
practice in metropolitan and suburban areas for many years.  Subscriber
locations in some rural areas, especially those served using open-wire pairs
or "REA cable", are still equipped with protector blocks containing fuses.

<> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
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