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From: lyndon@ncc.UUCP (Lyndon Nerenberg)
Newsgroups: comp.dcom.modems
Subject: Re: What is Max speed possible on phone lines?
Message-ID: <138@ncc.UUCP>
Date: Sun, 1-Nov-87 19:34:07 EST
Article-I.D.: ncc.138
Posted: Sun Nov  1 19:34:07 1987
Date-Received: Thu, 5-Nov-87 22:18:28 EST
References: <WANCHO.12345854244.BABYL@SIMTEL20.ARPA> <16064@topaz.rutgers.edu> <2174@kitty.UUCP>
Organization: Nexus Computing Inc.
Lines: 29
Summary: Twisted pair == long wire antenna

In article <2174@kitty.UUCP>, larry@kitty.UUCP (Larry Lippman) writes:
> 
> 	Actually, I don't believe that the FCC can do much about it.  The
> Ethernet transceivers certainly meet FCC emission requirements when used
> in a proper manner with coaxial cable (as intended).
> 	The problem comes to pass when people buy these $ 25.00 balun
> transformers which match coaxial cable to balanced line, and run them over
> unshieled telephone pairs.  The balun transformers themselves are just
> passive devices which need meet no FCC requirements of any kind; I can't
> envision their sale being "outlawed" or otherwise controlled.

Owning the parts is not illegal. Using them to build an radio transmitter
might be. Part 97 of the FCC regs pertains to permissable field strength
for unlicensed transmitters. It's not too generous (how far does your
kids walkie-talkie transmit). To be legal, you would have to ensure that
the field strength falls within the regs. I believe Part 97 also specifies
the ranges of frequencies you're allowed to use.

You could probably get away with it, but if someone complains about
interference you're SOL as far as the FCC is concerned.

> 	Wanna see something neat?  Try running two separate Ethernet
> circuits any significant distance in multi-pair telephone cable using
> these balun transformers.

Wanna see something *really* neat? Turn on an electric pencil sharpener
within about 10 feet of this wiring and watch your "Ethernet" die...

--lyndon  VE6BBM   {alberta,pyramid,uwvax}!ncc!lyndon