Article View: sci.electronics
Article #1056Re: RS-232 for voice
From: David R. Greenberg
Date: Thu, 03 Aug 1989 03:07
Date: Thu, 03 Aug 1989 03:07
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In article <6686@dayton.UUCP> J. Deters writes: >In article <8840@attctc.Dallas.TX.US> Steve Sampson writes: >[paragraph about serially digitizing audio data paraphrased] >>The quality is very acceptable. I tried the circuit at 8 kHz and it >>was just a little less than telephone quality. > >Only problem with this is the phone co. limits you to 3kHz bandwidth! > >There ain't no free lunch. Fortunately, quadrature amplitude modulation (QAM) has been used to transmit at 9.6 Kbps over the (slightly greater than) 3 KHz telephone bandwidth. In QAM, the pulses used to transmit data are shaped to fit the necessary bandwidth, but may have one of a discrete number of possible amplitudes and phases and therefore may contain several bits worth of information apiece. - David
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!apple!usc!bloom-beacon!mit-eddie!mit-amt!mit-caf!grnberg From: grnberg@mit-caf.MIT.EDU (David R. Greenberg) Newsgroups: sci.electronics Subject: Re: RS-232 for voice Message-ID: <2958@mit-caf.MIT.EDU> Date: 3 Aug 89 03:07:52 GMT References: <9185@kean.mun.ca> <3999@cps3xx.UUCP> <8840@attctc.Dallas.TX.US> <6686@dayton.UUCP> Reply-To: grnberg@mit-caf.UUCP (David R. Greenberg) Organization: Microsystems Technology Laboratories, MIT Lines: 20