chip@vector.UUCP (Chip Rosenthal) (12/14/87)
There was a question recently about converting touch tone to pulse dialing.
Unfortunately, it expired before I could grab it. If I remember correctly,
a module was suggested which would do this, but there was some question
as whether the thing was available.
An alternative might be a two part circuit: first convert the DTMF to
binary, and then the binary to pulse coding. Pulse dialers are very easy
to come by. Everybody has one.
The tougher part is the DTMF decoder. I've only seen two: a hybrid
module from Mitel and a monolithic IC from Silicon Systems. The SSI part
(SSI957) might be a cheaper approach. The thing is that you will need a
3.58MHz crystal (the decoder is a switched-C filter), and an op-amp (a
741 is shown in their datasheet) on the front end. I've never worked
with this part first-hand, but it looks like a pretty good solution.
This isn't quite a one-module solution to the conversion problem, but
it might be better than stringing together seven notch filters and
decoders.
SSI is at (714) 731-7110. I am not associated with any of these companies.
In fact, I'm a competitor. But we don't make dialers or DTMF decoders,
so you can buy theirs. :-)
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Chip Rosenthal chip@vector.UUCP | But if you want to sing the
Dallas Semiconductor (214) 450-0400 | blues, then boy you better
{texsun,codas,ihnp4}!killer!vector!chip | learn how to lose.