British Telecom CCITT No.7 common channel signalling: past, present and future

After extensive studies during the late 1960s, British Telecom decided that an integrated digital switching and transmission network would provide the most economical telecommunications infrastructure for the future. The authors describe British Telecom´s experience of specifying, installing, enhancing and managing a complex signalling network. They highlight the need for strict enhancement upgrade control procedures and validation of interworking compatibility between different implementations of CCITT No.7 to ensure continued network coherence. The future evolution of CCITT No.7 signalling embracing non-circuit relating signalling transaction capabilities, and the concepts for providing new customer services are discussed