PULSE CODE MODULATION (PCM)

Modulation in which a signal is sampled, and the magnitude (with respect to a fixed reference) of each sample is quantized and digitized for transmission over a common transmission medium . ( 188 ) Note 1: In conventional PCM, before being digitized, the analog data may be processed ( e.g., compressed), but once digitized, the PCM signal is not subjected to further processing ( e.g., digital compaction) before being multiplexed into the aggregate data stream . Note 2: PCM pulse trains may be interleaved with pulse trains from other channels.