Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!haven!mimsy!tank!uwvax!puff!cat27!boettche
From: boettche@cat27.CS.WISC.EDU (Michael Boettcher)
Newsgroups: sci.electronics
Subject: Audio signal compression needed
Message-ID: <2272@puff.cs.wisc.edu>
Date: 17 Feb 89 01:11:48 GMT
Sender: news@puff.cs.wisc.edu
Reply-To: boettche@cat27.CS.WISC.EDU (Michael Boettcher)
Distribution: usa
Organization: U of Wisconsin CS Dept
Lines: 26

I am looking for a device or some way of allowing me to use my modem, and 
talk to the person on the other end of the line.

I was thinking that if there isn't a source of such a device at a reasonable
(for a college student) price, that it souldn't be too dificult to make
something like this.  

If the output of a microphone/amp were put into a IC that compresses the
frequency band down to a few hundred hertz (assume 3000 hz band to begin
with) it could be placed on top of the band that the modem is using.  If 
the person at the other end of the line had something to decompress the data
and send it to a speaker, the people on both ends of the line could talk.

There are a few things that would need to be done, such as filtering the 
signal for each (modem and speech circuit).  My main question is if the 
voice signal can be compressed by a factor of ten, and if there is enough 
room at the top (or bottom) of the band sendable by the phone lines to 
place the compressed signal.  I have heard that the phones only have a 
3000hz bandwidth.

Anybody have any information that would help?

Thanks in advance.

Michael Boettcher   Student, University of Wisconsin, Madison
                    boettche@garfield.cs.wisc.edu