reason the new reference is entitled The Cable and Telecommunications Professionals' Reference. Some of the content in the earlier edition has become dated, and a substantial amount of new mate- rial is now included SO that it remains an authoritative reference book. However, some of the earlier content remains fundamentally relevant and is retained in this volume. Inevitably this means that some of the earlier material relating to the displaced technologies should, in some cases, be downsized and in other cases removed. Even so, the huge amount of new material entering the scene means that the full scope would lead to a significant increase in the length of the book. The current edition is therefore divided into three volumes, and I have attempted to associate related material in each. Because of the many relationships between different topics, however, it is not possible to split them into three completely independent volumes. The first volume dealt with the telecommunications industry and with voice and data and their convergence in both landline and mobile cellular networks. This seemed a logical grouping because of the historical influence of telephone networks on today's communica- tions systems. This volume deals with core transport network technologies and the changes that are enabling them to deal with converged voice, data, and video traffic. The third volume will deal with the broadband access network technologies and the way in which they are used to support new services. Volume 2 of The Cable and Telecommunications Professionals' Reference is arranged into three parts. The parts deal firstly with the digitization and coding of source information, secondly with the properties of the transmission paths across which the signals are carried, and thirdly with the networking techniques that are used to ensure that the signals reach their destination. Because of the growth in demand for data services and the way in which voice, data, and video services have converged, core transport networks have needed to 