运用FFT技术来综合和分析电话拨号的过程，matlab来分解了这一过程，希望能提供帮助- TOUCHTONE　Use FFT to synthesize and analyze telephone dialing

The dual tone multi-frequency (DTMF) standard specifies that the tone

generated by a button on a telephone key pad is the sum of two sinusoids,

with frequencies determined by the button s row and column.

The dial pad on the upper left allows you to select buttons and generate

the corresponding tones.

The signal plotted on the upper right is a recording of the FAX number

for the MathWorks being dialed.　You can replay the entire signal, or

select individual segments.　The power plot is the magnitude of the FFT

of the signal being played.　What is the MathWorks FAX number?