Abstract :
The advent of pulse code modulation (p.c.m.) techniques heralds the possibility of extremely reliable and completely distortionless distribution and processing of audio signals. In this paper, the basic requirements for audio circuits of broadcast quality are reviewed, and the specification of a p.c.m. system satisfying these requirements is developed. Means for reducing the required number of digits, without sacrificing quality, are considered. The use of p.c.m. as a means of distributing sound signals for radio must await the availability of p.c.m. circuits of sufficient capacity. However, the links already in use for video signal distribution are of sufficient bandwidth for p.c.m. sound, and the idea of combining the sound signal with the accompanying video signal as a means of television programme distribution is very attractive. A short description is given of a method of composite sound and vision distribution by means of pulse code modulated sound inserted into the 625-line television waveform during sync pulse periods. Finally, the feasibility of a widespread adoption of p.c.m. within studio centres is examined, and prospects for digital mixing, recording and artificial reverberation are considered.
