Signalling is the life-blood of telecommunications, transforming inert network elements into a powerful medium capable of providing services to customers. The modern trend is to introduce digital technology, particularly integrated services digital networks, and these conditions allow the full benefits of common-channel signalling (CCS) systems to be unleashed. CCS systems have a vast repertoire of signals and a high speed of operation. These attributes, coupled with the derivation of signalling networks that are separate from other traffic, provide a major step in the evolutionary process towards unimpeded signalling-information transfer between customers, between customers and network nodes, and within networks. This book is aimed at a wide variety of readers. It is written to allow a novice to start with basic principles and build up a wide appreciation of CCS systems. Those readers who already have a knowledge of telecommunications, and wish to derive a better understanding of CCS systems, can select the more advanced chapters and avoid the basic concepts. The book is also intended to be used by experts in the CCS field as a reminder of terminology and concepts and to widen knowledge of CCS beyond a specific area. The book starts with the principles of signalling systems in Chapter 1. Chapter 2 reviews the categories of channel-associated signalling systems and chapter 3 summarizes CCITT Signalling System No 6. However, the focus is upon modern/CCS systems and these are explained in Chapters 4 to 10. A fundamental attribute of modern CCS systems is evolutionary potential. Its architecture, described in Chapter 4, is a key to its success. Chapters 5 to 7 describe the inter-nodal CCS system CCITT Signalling System No 7. Chapters 8 and 9 describe the CCITT digital subscriber Signalling System No 1. The interworking of CCS systems is explained in Chapter 10 and Chapter 11 reviews the book and draws some conclusions on how to meet customer needs in rapidly changing times.
