Re: DTMF

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Article #17841

#17841

From: Paul Dietz
Date: Wed, 22 Jul 1987 16:02

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In article <17966@cmcl2.NYU.EDU> hanley@nyu.arpa (John Hanley) writes:
>Addendum:  Bandpass active filter  (40 db/decade, I think -- it's 2nd order)
>
>                                   R                 R
>                           +----/\/\/\/-----+-----/\/\/\/-----+
>                           |                |                 |
>                         ----- C          ----- C           ----- C
>                         -----            -----             -----
>                           |                |                 |
>                           +----------------+-----------------+
>                           |                |    R/12         |
>                  Rin      |   |\           +--/\/\/\/--GND   |
>audio in  o-----/\/\/\/----+---| -\___________________________+------o Vout
>                             +-| +/
>                             | |/
>                             |
>                            GND
>
>where Rin is whatever input impedance you would like to present to your
>RF reciever circuitry, and RC determines the detection frequency:
> f = sqrt(3) / ( 2 pi R C )

I don't think this is what you meant. None of the RC's (except Rin) are
doing anything!

Paul H. Dietz
Carnegie Mellon University

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Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!seismo!rochester!pt!speech1.cs.cmu.edu!phd
From: phd@speech1.cs.cmu.edu (Paul Dietz)
Newsgroups: sci.electronics
Subject: Re: DTMF
Message-ID: <1010@speech1.cs.cmu.edu>
Date: Wed, 22-Jul-87 12:02:41 EDT
Article-I.D.: speech1.1010
Posted: Wed Jul 22 12:02:41 1987
Date-Received: Fri, 24-Jul-87 04:49:48 EDT
References: <1377@mit-amt.MEDIA.MIT.EDU> <17966@cmcl2.NYU.EDU>
Distribution: na
Organization: Carnegie-Mellon University, CS/RI
Lines: 27
Keywords: dtmf remote control

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