This book provides an up-to-date and thorough grounding in the concepts of modern digital transmission. It is written in a pedagogic style, aimed at enabling readers to understand the fundamental concepts and processes. System descriptions are included, however the text also explains the basic techniques of transmission, and includes the necessary mathematical background. The basic processes, such as matched filter detection, pulse shaping, line coding, channel coding, error detection and correction, etc. are described in the central part of the book. Understanding the concepts behind these processes requires a grasp of basic mathematical models, and this is provided in the first part of the book. Finally, to put the processes in context, the third part describes elements of the public switched telephone network. The book is written throughout in a modern, digital context, and is comprehensively illustrated with helpful figures. Although the models (time- and frequency-domain concepts) have wider relevance, they are developed specifically for modeling digital systems. The processes described are those found in current transmission systems, and the description of the PSTN includes an outline of newly formulated standards for the synchronous digital hierarchy (SDH), SONET and for broadband ISDN (ATM).