单音多频信号的产生和识别，采用FFT变换。应用于电话拨号。是学习数字信号处理的大作业。-Tone multi-frequency signal generation and recognition, the use of FFT transform. Applies to telephone dial-up. Digital Signal Processing is the study of large operations.

DTMF的数据fft分析，每个键值的波形和频谱都有显示，有GUI界面-DTMF data fft analysis, waveform and spectrum of each key has revealed that there is a GUI interface