Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!pasteur!ames!coherent!mailcom!Ploni.Almoni
From: Ploni.Almoni@mailcom.FIDONET.ORG (Ploni Almoni)
Newsgroups: sci.electronics
Subject: Re: Audio signal compression needed
Message-ID: <3956.23FEA32A@mailcom.FIDONET.ORG>
Date: 18 Feb 89 20:11:01 GMT
Organization: MailCom Public USENET, Palo Alto CA (415) 855-9548
Lines: 26

Michael -- you are on the right track but are going sideways!!
  
What you want already exists, but the way it is done is to leave the 
audio signal as is and to carry the DATA channel in a narrow bandwidth 
either just outside the normal audio bandwidth (above or below) or to 
superimpose the data channel in a "hole" chopped into the audio spectrum.
  
The first method is done on certain types of AM broadcast transmitters to 
telemeter transmitter data or control things like electric meter 
switching, and the second method is most common in telephony.
  
The data rate is usually 300 baud although the same technique could be 
used for higher rates.
  
HOWEVER - this is not a "home electronics" do-it-yourself project, and 
the modems involved cannot be found on the pages of Computer Shopper! 
They are not cheap, in other words.
  
Hope that helps somewhat to dispel the fog.           -=Ploni=-
  
  



--  
Via  apple!mailcom, Fido 1:204/444