a) Coding where analog input signal is represented by a given number of fixed-width digital samples per second.

Often used for the coding employed in the telephone network. b) A technical term for an analog source waveform, for example, audio or video signals, expressed as periodic, numerical samples. PCM is an uncompressed digital signal. c) This is a form of the digital audio signal used for both CD and laserdisc. It is a serial data stream that is coded for transmission or recording. PCM is also used for many other types of serial data communications.