The chapter begins with a discussion on the need of transition towards digital communication systems and the role of repeaters. This is followed by a discussion on how to represent message in the form of pulses. Sampling theorems for both low pass and band pass signals are discussed. The technique of representing message signal by modulating an attribute of sampled pulses like amplitude (PAM), width (PWM), position (PPM) are discussed with their merits and demerits. It is shown that PAM is ideally suited for time division multiplexing (TDM) and digital encoding. Different digital encoding schemes with related quantization errors are discussed. The role of linear prediction is highlighted. Standard voice coding schemes are presented which forms the basis of digital voice communication. Numerical and MATLAB examples are used to enhance conceptual development.
