Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: 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 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