Article View: sci.electronics
Article #9831Re: Telephone Lines
From: Bob Myers
Date: Mon, 28 Jan 1991 20:05
Date: Mon, 28 Jan 1991 20:05
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>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.
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!sdd.hp.com!hplabs!hpfcso!hpfcdj!myers 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