 (and therefore bandwidth) needed to carry analogue signals that have been digitized without significant loss of quality. Part 1 of Volume 2 of The Cable and Telecommunications Professionals' Reference looks at the process of digitizing analogue signals and at the properties of the Part 1 resulting voice, data, and video signals. Chapter 1 describes the properties of speech signals and the principles involved in converting voice signals into digital format. Pulse code modulation, which has been the basic format for digital voice signals in the Public Switched Telephone Network since the first digital systems appeared in the 1960s, is explained along with basic digital multiplexing and trans- mission performance. Chapter 2 describes the basic principles of data transmission, including modulation schemes and synchronization, and summarizes recent trends in data transmission. Chapter 3 discusses the principles of digital video transmission, including an overview of compression methods and a description of the ways in which spatial, temporal, and statistical redundancy can be exploited to minimize the information content to be transmitted. The particular requirements of video signals for transport over the Internet are a topic of particular importance, and this is also described. When digital information is transmitted across a telecommunications channel, very small proportion of the digits transmitted might be incorrectly detected at the receiver. While Chapter 3 is concerned with removing redundancy from the source signal ("source coding"), Chapter 4 is concerned with adding a small amount of redundancy to the transmitted signal SO that errors arising during transmission can be detected and corrected at the receiver. This is known as "error control coding." Voice Transmission Stuart D. Walker Rouzbeh Razavi University of Essex Speech-Coding Principles Speech coding is the process of obtaining a compact representation of voice signals for efficient transmission over band-limited channels or for storage. Today, speec