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Path: utzoo!linus!decvax!tektronix!azure!bronze!stevesu
From: stevesu@bronze.UUCP (Steve Summit)
Newsgroups: net.followup
Subject: Re: Modem Users Beware: BELL $$$
Message-ID: <857@bronze.UUCP>
Date: Tue, 18-Oct-83 21:23:43 EDT
Article-I.D.: bronze.857
Posted: Tue Oct 18 21:23:43 1983
Date-Received: Sun, 23-Oct-83 08:40:01 EDT
References: <711@ihuxr.UUCP>
Organization: Tektronix, Beaverton OR
Lines: 59

Although I hope they don't choose to do so, the phone company can
quite legally determine if you're using a modem.  In fact, they
do it already, and you should be glad they do.  Long distance
trunks all have devices called echo suppressors.  These disable
transmission in one direction when something is going in the
other.  Without them, your voice would bounce off the other end
and you'd hear it a second later.  (Contrary to submissions
elsewhere on the net, there can be a lot of propagation delay on
a phone call, particularly if it travels via satellite. 
Furthermore, older local trunks are often heavily loaded, which
improves the audio characteristics at vocal frequencies, at the
expense of a significant delay and severe bandwidth limitation. 
Modems don't work at all on loaded lines)  When you realize that
phone calls are bidirectional and have LOTS of gain, it's
surprising that there isn't more echo and feedback.  It's due to
echo suppressors that it's usually hard to interrupt someone on a
long-distance call.  They simply can't hear you.

Anyway, the point of all this is that an echo suppressor would
obviously keep two modems from talking to each other, since each
has to continuously send the other a carrier.  For this very
reason, each and every echo suppressor in the entire phone system
has a modem detector in it, which turns off the echo suppression
in the presence of sustained carrier frequencies.

When you stop and think about it, the phone company monitors your
call in a lot of other ways, too.  They notice when you hang up,
so they can release the common circuitry.  They keep track of how
long the call lasts, so they can bill you.  I've heard that some
central offices notice if you're using a touch-tone phone (since
the vast majority of lines now seem to support them) and ask you
to pay for touch-tone service if you're not already.  None of
this is 1984.

It certainly isn't fair to unilaterally charge modem users more
for their local connect time.  I know I spend far less time on
the phone using a modem than my little brother does talking to
his girlfriend.  The argument that a long-distance modem call
ties up two trunks all the time while conversation can be
multiplexed is a good one.  However, the proposal being discussed
is for the local office to charge more for connect time for a
local user, which (after January 1) has nothing to do with the
long-distance connections.

Audio modems are in fact incredibly wasteful, especially on
long-distance trunks.  After your modem cleverly disguises 300 or
1200 bits/second to look like an audio signal (yes, I know baud
!= bits/sec, but it's close) the phone company turns right around
and digitizes the audio, at a  MUCH higher baud rate.  Even when
direct data connections become available (and this will certainly
happen soon) I'll still need my audio modem becqause I call up a
lot of rinky-dink computers that will keep their audio dialups
for a long time before converting.  At risk of repeating what's
been said already (I hate people who do that!) it would be fine
to charge people more for using more connect time, but not just
for the fact that their audio is generated by a modem and not
their vocal cords.
                                  Steve Summit
                                  tektronix!tekmdp!bronze!stevesu