Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pacbell!ditka!qiclab!sopwith!snoopy
From: snoopy@sopwith.UUCP (Snoopy)
Newsgroups: comp.dcom.modems
Subject: Re: Where is modem progress?
Message-ID: <182@sopwith.UUCP>
Date: 27 May 89 15:27:57 GMT
References: <78700004@p.cs.uiuc.edu> <8196@killer.DALLAS.TX.US>
Reply-To: snoopy@sopwith.UUCP (Snoopy)
Organization: The Daisy Hill Puppy Farm
Lines: 37

In article <8196@killer.DALLAS.TX.US> elg@killer.DALLAS.TX.US (Eric Green) writes:

| In 1983, when I first got into telecommunications, a Hayes 1200
| Smartmodem costed over $500, and the best deal around for a 1200 baud
| modem was around $350. The standard, of course, was still 300 baud.

In '83 stupid 1200 baud modems were common inside Bell Labs.  (pick up
data phone, dial computer, push button on modem/cord, hang up phone)
I have no idea what they paid for them.  I found it a bit annoying to
be limited to 1200 baud talking to a machine in the same building.  (In
their defense, it was a convienant way to provide switching.)

| As a result, your
| beautiful digital data is analogized, spit onto the phone line where
| it is then re-digitized and spit over fiber optics at 64kbaud or so,
| then re-analogized at the other end into a nice slow analog signal. I
| believe the signal bandwidth is 7khz. A telephone expert could be more
| exact.

In the Bell/AT&T worlds, phone lines are sampled at 8 kHz.  Samples are
8 bits.  The bandwidth is thus guaranteed to be less than 4kHz.  I recall
numbers of something like 3400, I suspect this varies a lot with the age
of equipment and so on.  Don't expect to see very high order filters
to squeak out every last Hz like you do on CD players, lots of phone
equipment is old.

Like it or not, the phone system was not designed for high fidelity stereo
or computer data transmission.  It was designed for voice communication,
period.  Unfortunately it doesn't always accomplish even that.  :-(

Sort of amusing remembering my EE communications prof stating that 1200 baud
was the absolute maximum one could get over a phone line.  *grin*
    _____     
   /_____\    Snoopy	"My dot-matrix does Postscript."
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