Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!linus!security!genrad!decvax!tektronix!ogcvax!omsvax!icalqa!hplabs!hao!seismo!rlgvax!cvl!umcp-cs!cal-unix!wise
From: wise@cal-unix.UUCP
Newsgroups: net.general
Subject: Re: Re: delays in phone propagation
Message-ID: <142@cal-unix.UUCP>
Date: Wed, 12-Oct-83 10:00:45 EDT
Article-I.D.: cal-unix.142
Posted: Wed Oct 12 10:00:45 1983
Date-Received: Thu, 20-Oct-83 04:25:56 EDT
Lines: 35


	Regardless of the routing of your call (which may  take  the
	several  seconds  you  describe), the phone communication is
	approximately light-speed.  Yes,  there  are  finite  delays
	involved  in  the  switching circuitry, but remember back to
	the most recent coast-to-coast phone call you made.  Did you
	notice  a  big  lag  in  talking  to the other person?  I'll
	warrant not.  As far as I know, the WWV dial-in  is  located
	in  the  continental  US, (and probably some place centrally
	located), so at least you will have a delay of

		2,000mi / 186,000mi/sec = .01 sec + electronics delay

	(Or not very much delay at all).

		-Dan Klein, Mellon Institute, Pittsburgh

This is all essentially true, at least from the viewpoint of physics
(ignoring the fact that the speed of propagation of a signal in wire
is closer to 120,000mi/sec).  The problem is that I think the telephone
companies have started using satellites, which I think packet switch,
which could lead to delays on the order of seconds.  I don't know how
many telephone companies use satellites for intracontinental traffic,
but I'm pretty sure that at least some do.  I would expect this to
become more widespread as the cost of satellites decreases with respect
to the cost of maintaining long land lines or microwave links.

Before anybody flames; yes, I know, the difference in delay caused by
propagation at c versus the real propagation rate is not that much, 35%
to be exact, since I used a velocity constant of .65, meaning that the
above .01 + K (K = electronic delay, above) delay becomes .017 + K.  It's
K, and the magnitude of K as caused by satellites that I'm commenting on.

Rick Wise
ucbvax!decvax!harpo!seismo!rlgvax!cal-unix!wise