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

On Wed, Dec 2, 2009 at 2:51 PM, Bruno L. Albrecht <brunolalb@gmail.com> wro=
te:
> Hi,
> I'm trying to separate 3 frequency components from an analog signal. The
> original signal is composed by the sum of 3 frequencies (1500, 4000 and
> 10200 Hz) and some noise. The objective is to separate only those 3
> frequencies and evaluate their magnitudes. I thought about lots of ways of
> doing it, but couldn't get an effective one.
> Any ideas?
>
> Cheers,
> =A0Bruno
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