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From: myers@hpfcdj.HP.COM (Bob Myers)
Newsgroups: sci.electronics
Subject: Re: Telephone Lines
Message-ID: <17660147@hpfcdj.HP.COM>
Date: 28 Jan 91 20:05:34 GMT
References: <4574@mindlink.UUCP>
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 24

>While in a meeting, one technical "guru" declared that my statement was wrong
>when I said that a telephone was a form of transmission line.  The "guru"
>across the table from me declared that, not only was I totally wrong, but that
>he and a senior engineering in the company had "proven" that a telephone line
>was not a transmission line nor could it be modelled as such.  So, is a
>telephone line a form of transmission line or am I totally wrong as this "guru"
>declare?


Well, of COURSE it's a transmission line; after all, it carries an electrical
signal from over THERE to over HERE, doesn't it?  But what I suspect is
meant here is that telephone transmission cannot be accurately modelled
completely using the simple transmission line theory we all get in first-year
communications classes ("Here's a load impedance, here's the source 
impedance, and here's the characteristic impedance of the line, and that's 
it."), and I suspect they're right about that.  For one thing, the line length
is horrendous and there's probably a fair amount of losses via radiation and
coupling to other structures, and a raft of other other effects more exotic
than what's typically covered in the simpler models.


Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
myers@fc.hp.com                          |  sentient life-form on this planet.