On Wed, Dec 2, 2009 at 9:01 PM, andrew kelley <leetslacker@gmail.com> wrote:
> Use a discrete fourier transform.
>
> http://www.dspguide.com
> http://www.dattalo.com/technical/theory/dtmf.html
> http://en.wikipedia.org/wiki/Discrete_Fourier_transform
> http://en.wikipedia.org/wiki/Discrete-time_Fourier_transform
>
> Andrew

If you're only looking for a single frequency, you don't have to do
the full spectrum DFT... you can just calculate the frequency
components in question.
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