This text sets out to familiarize readers with the latest advances in signalling, specifically in the context of cell relay, frame relay and ISDN. It is aimed at network managers, equipment developers, communication software developers, information providers and sophisticated end-users. It describes the important evolving communication capabilities of public networks; and the ensuing opportunities for designing sophisticated enterprise networks supporting user applications such as high-speed data, multitone, multipoint videoconferencing, video dialtone and high-resolution image transfer. It also explores the importance of digital signalling in evolving high-speed networks; gives explanations of UNI ATM signalling, and others; and discusses future trends.