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 Repeater-Builder@yahoogroups.com, 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...
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