PCM

A modulation technique in which an analog signal is encoded, i.e., converted from analog to digital format. The term generally is applied to the conversion of voice from a continuous analog waveform to digital pulses as specified in ITU-T Recommendation G.711, which is based on the Nyquist theorem. That theorem states that an analog signal waveform can be converted to digital format and be reconstructed without error from samples taken at equal time intervals, if the sampling rate is equal to, or greater than, twice the highest frequency component in the analog signal. As the voice band is 0