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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: DTMF
Message-ID: <1852@kitty.UUCP>
Date: Fri, 17-Jul-87 23:42:45 EDT
Article-I.D.: kitty.1852
Posted: Fri Jul 17 23:42:45 1987
Date-Received: Sat, 18-Jul-87 18:28:51 EDT
References: <1377@mit-amt.MEDIA.MIT.EDU>
Organization: Recognition Research Corp., Clarence, NY
Lines: 26
Summary: Try SSI or Mitel

In article <1377@mit-amt.MEDIA.MIT.EDU>, jh@mit-amt.MEDIA.MIT.EDU (John Underkoffler) writes:
> 	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.

	Try using Silicon Systems Inc. products such as their SSI201,
SSI202, SSI203 or SSI204.  These products all take an analog input and
provide a BCD digit output.  They all use 3.58 color burst crystals
for the reference frequency.  I have had good luck with SSI products.
	Or you can try Mitel products such as their MT8862 and MT8865
(used together, the former is the decoder and the latter is a filter),
or the integrated MT8870A.  The Mitel devices are better quality, but
also cost more money.
	In my opinion, you would be MUCH better off with the above devices
rather than attempting to build a discrete DTMF decoder using, say 567
PLL tone detectors.

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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