Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!apple!rutgers!cmcl2!rocky8!cucard!ccnysci!alexis
From: alexis@ccnysci.UUCP (Alexis Rosen)
Newsgroups: comp.dcom.modems
Subject: Re: Which is best? (USR vs Telebit)
Keywords: Telebit elegance
Message-ID: <943@ccnysci.UUCP>
Date: 23 Oct 88 05:25:45 GMT
References: <9515@conexch.UUCP> <25339@tut.cis.ohio-state.edu>
Reply-To: alexis@ccnysci.UUCP (Alexis Rosen)
Lines: 20

In article <25339@tut.cis.ohio-state.edu> paul@morganucodon.cis.ohio-state.edu (Paul Placeway) writes:
>Besides, the Telebit protocol seems to still have room to grow.
>Assuming an optimal line, giving 512 channels through it, at 30 baud
>per channel, 2 bits per baud, that gives an effective total bandwidth
>of 30720 bps.  Assuming that they can squeeze more bits/baud or more
>baud/channel, speeds can go up from there.

I'm no expert on this, but isn't the top limit for phone lines about 20kbps,
based on Shannon's equation?  (This doesn't count compression, of course.)
This assumes that phones still operate between 300 and 3300 hertz, and that
the S/N ratio is 100:1. As far as I recall, this is an absolute number,
unaffected by modulation schemes.

I got the numbers from Cole's Computer Communications, 1982.

----
Alexis Rosen                       alexis@dasys1.UUCP  or  alexis@ccnysci.UUCP
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