ABSTRACT
Pulse code modulation Pulses may be sent along a cable as a sequence of high and low voltage levels but, for transmission by radio, optical fibre and also by cable, they are more often modulated on to a carrier frequency. This is pulse code modulation, as described on p. 166. PCM is the most widely used technique for transmitting digital and (after conversion) analogue data. Bursts of the carrier frequency, representing '0's and ' l ' s , are transmitted and then demodulated at the receiver.
