The publications presented arc divided into those constituting the core of the submission and those which are considered to be of secondary material. In Section 2 a commentary on the core research publications identifies two closely related themes. The first theme, presented in Section 2.1, discusses my published articles on delta modulation and digital encoding of speech and picture signals. While conducting research into digital encoding I became involved with techniques for combating the effect of transmission errors in digitally encoded speech and picture signals, and my publications on this subject are described in Section 2.2.