Although the enhancement of System 12, SEL's digital switching system, for ISDN services is virtually complete, further development work is being carried out to allow broadband switching for videophone services, videoconferencing, and the distribution of radio and television programs. This paper describes an appropriate approach to the evolution Of System 12 toward the broadband ISDN (B-ISDN), emphasizing the crosspoint and technology aspects of the broadband switch. Test results on a broadband switch VLSI circuit for 140 Mbit/s in a 2μm CMOS technology are presented.

Subscriber stations in service integrated communications systems can be implemented in many different ways. Within the HHI Broad-Band Communications System two extremely different solutions have been realized: on the one hand, subscriber stations in a conventional star type network with central exchange and analog transmission, and on the other hand, subscriber stations in a digital, loop-structured network employing distributed control. In both cases, the same services (telephone, data, videophone, TV, and stereo broadcasting) are carried to the subscriber via one single optical fiber. This paper describes these different realizations of service integrated subscriber stations in detail. The size of terminal equipment, power consumption, extendability to further subscribers, and services and reliability are the main parameters of an appropriate comparison. An analysis of both realizations, giving emphasis to the switching and multiplexing, and the feasibility of analog optical transmission will be made. Alternative realizations and an estimation concerning subscriber stations for future service integrated broad band communications systems will be presented.