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From: jh@mit-amt.MEDIA.MIT.EDU (John Underkoffler)
Newsgroups: sci.electronics
Subject: DTMF
Message-ID: <1377@mit-amt.MEDIA.MIT.EDU>
Date: Fri, 17-Jul-87 15:51:40 EDT
Article-I.D.: mit-amt.1377
Posted: Fri Jul 17 15:51:40 1987
Date-Received: Sat, 18-Jul-87 16:42:57 EDT
Organization: MIT Media Lab, Cambridge, MA
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Posting-Front-End: GNU Emacs 18.44.1 of Mon Jun  1 1987 on media-lab (berkeley-unix)



	Does anyone know who (if anybody) is making DTMF decoder
chips? Neither the TI nor the Motorola "Communications Databooks" as
recently as 1985 shows that any such chip exists (although there are
plenty of DTMF encoder chips available). Ideally, I'd want a chip
which accepts an analog input and produces either a digital hex output
(in the range 0-15)or a "row and column" output indicating the
position of the button on the imagined phone from which the signal
came.
	The point of all this is that I'd like to selectively activate
one of sixteen (or twelve, or whatever) devices by radio remote
control, and it seemed to me that one of the easiest ways to realize
this would be to follow the phone company's lead and transmit
voice-frequency DTMF tones (via disemboweled walkie-talkie); each
target unit could then be constantly receiving the same radio
frequency transmission; simple logic stuff inside the unit would then
read the output of the local DTMF decoder chip and decide if it should
activate the associated mechanism.
	Comments? Ideas? Insults?

				John "Wombat Stomper" Underkoffler
				alias "jh@media-lab.media.mit.edu"