Analog transmission is not particularly efficient. When the signal-to-noise ratio of an analog signal deteriorates due to attenuation, amplifying the signal also amplifies noise. Digital signals are ...

This report describes a series of subjective tests made to discover whether instantaneous companding could profitably be applied to a pulse-code-modulation system designed for high quality sound ...

The various methods for converting analogue signals into the form of pulse-code modulation and back again are reviewed. Reasons are given for preferring a particular method of conversion called ...

For technical and economic reasons, the present network of lines used for distributing sound signals to transmitters at audio frequencies will eventually have to be replaced by some telecommunication ...