There is a simple algorithm which can be used to detect DTMF or PL tones. I believe the name is the Goertzel method. Basically it consists of multiplying the expected tone frequencies with the incoming audio. These frequencies come from a lookup table that you create. The idea is that then you low pass filter the result (integrate) and a tone near the desired frequency creates DC or a low frequency beat that can be detected.
I have built working versions of this for touch tone detection. The processing used up all of the speed in a 4MHz 8 bit 6805 processor. It should be easily doable on any modern PC. Some of the hardware solutions available do this internally. You might look at www.cmlmicro.com. They have a number of signalling chips. They have CTCSS and others that do DTMF. Perhaps you'd realy want to have the thing entirely in software. I wouldn't tackle it in windows, but it ought to be straight forward in Linux. 73 Ed K3SWJ --- In [email protected], Don Pomplun <[EMAIL PROTECTED]> wrote: > > What's that company that makes the little CTCSS encode/decode boards for > $50. Is theirs a standard chip, or custom? Except for the NIH syndrome, > it would seem cheaper just to add their board into your design. And, of > course, DTMF decode chips are all over the place. > Regards, > Don > > At 04:35 PM 4/22/2005 -0400, you wrote: > > >Mike Morris WA6ILQ wrote: > > >>--- Nick Papadonis <[EMAIL PROTECTED]> wrote: > > >>>Is anyone aware of either hardware or software > > >>>components to decode PL > > >>>tone, DTMF and CTCSS? Open source software is > > >>>preferred. > > > > >> > > >>There was a program called WinTone that would do this. > > >>Not sure where to find a copy of it on the internet > > >>now as they seem to have been taken off. Think the > > >>last one was version 2.02 > > > > > > > > > As soon as I heard that it was being dropped I made > > > sure that there is a copy on www.repeater-builder.com ... > > > use the search function on the main page. > > > >Thanks Folks, but this is only an executable, no source code for FFT etc... Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
