The book presents the current standards of digital multiplexing, called synchronous digital hierarchy, including analog multiplexing technologies. It is aimed at telecommunication professionals who want to develop an understanding of digital multiplexing and synchronous digital hierarchy, in particular, and the functioning of practical telecommunication systems, in general. The text includes all relevant fundamentals and provides a handy reference for problem solving or defining operations and maintenance strategies. The author covers digital conversion and TDM principles, line coding and digital modulation, signal impairments, and synchronization, as well as emerging systems.