The paper presents an approach to ISDN suitable both for a pilot service, to be carried out in the near future in Italy, and for long-term developments with a high degree of penetration of ISDN setvices. Integration of ISDN services in the digital telephone exchange "UT" has taken place at all levels: system architecture, subscriber access structure, circuit connecting network, transmission links, call processing, and 0 & M functions. We also describe a new protocol that facilitates the dialog between exchange modules and between different exchanges for the data service. It is suitable for implementing packet transit switches with low complexity, high throughput, and low transit time. A special peripheral-handling processor handles the most repetitive functions of the protocols both in the local exchange and in other parts of the network, while the exchange central processor performs the ISDN call-handling functions; the same peripheral processors and the same module processor are used for both ISDN and telephone services. Finally, the paper shows how this architecture can evolve to include new wide-band services and new techniques to implement high-capacity fast packet switches.

An experiment of wide-band switched interactive services (video services) is presented. The experiment, named WISE (Wide-Band Interactive Services Experiment) is limited to a small number of subscribers but is representative of a future domestic environment. After a brief presentation of the scope of the activity, the video services that have been implemented, both unidirectional and bidirectional, are described. The system organization, based on a wide-band switching matrix and on the transmission of video signals on a single optical fiber by wavelength-division multiplexing, is then discussed, and the solutions adopted for the transmission equipment are examined. The structure of the service center is afterwards described, together with the subscriber procedures required to access the different services. Finally, some improvements and future possible developments of wide-band interactire systems are briefly highlighted.