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From: boomer@athena.princeton.edu (Don Alvarez)
Newsgroups: comp.dcom.telecom
Subject: Re: Phone Calls at the Speed of Light
Message-ID: <3396@accuvax.nwu.edu>
Date: 31 Jan 90 15:08:25 GMT
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Reply-To: Don Alvarez <boomer@athena.princeton.edu>
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X-Telecom-Digest: Volume 10, Issue 67, message 5 of 11


In article <3335@accuvax.nwu.edu> eli@pws.bull.com writes:

>The speed of light in fiber is actually slower than the speed of light
>in coax cable...  (.72 to .76, or some such).  Does anyone know the
>propagation speed for light in copper phone wire, or whatever else is
>used for long lines??

 From the Reference Data for Radio Engineers, published by the Federal
Telephone and Radio Corporation (an associate of the International
Telephone and Telegraph Corporation) Copyright 1943.

		Telephone Transmission Line Data
Characteristics of Standard Types of Aerial Wire Telephone Circuits
			At 1000 Cycles Per Second

Type of Circuit		Gauge	Spacing	Velocity
			(mils)	(in.)	(miles/s)
Non-Pole Pair Physical	165	8	179,000
Non-Pole Pair Side	165	12	179,500
Pole Pair Side		165	18	178,000
Non-Pole Pair Phantom	165	12	177,500
Non-Pole Pair Physical	128	8	178,000
Non-Pole Pair Side	128	12	178,500
Pole Pair Side		128	18	177,000
Non-Pole Pair Phantom	128	12	177,000
Non-Pole Pair Physical	104	8	175,500
Non-Pole Pair Side	104	12	177,000
Pole Pair Side		104	18	175,500
Non-Pole Pair Phantom	104	12	176,000

Notes:	(1) All values are for dry weather conditions and 20Degrees C
	(2) All capacity values assume a line carrying 40 wires
	(3) DP (double petticoat) Insulators assumed for all 12" and 18"
		spaced wires - CS (Special Glass with Steel Pin) Insulators
		assumed for all 8" spaced wires.

Since the slowest speed listed here is about 94% C, and one can only
assume wires have gotten better, not worse in the last 47 years, we
clearly should all drop our fiber optic lines and go back to copper.
(God, how I hate waiting for those 20ms delays!)

-don