Abstract: Many telecommunication switches operate in dual plane mode for better reliability and maintainability. For ATM switches, it has been difficult to merge cells emerging from two identical planes because of the non-synchronous nature of transmission. An ATM plane merging filter is disclosed. The filter contains memory to store the first of a pair of identical cells under control of filter control means. The filter control means monitors the headers of the cells and sends an enabling signal to the memory for cell storage when no identical cell is in storage.

Abstract: A double-star communications system comprises a digital terminal, active pedestals coupled to the digital terminal via optical fibers, and subscribers' premises coupled to each active pedestal via existing telephone lines and via additional communications paths, which may comprise optical fibers or coaxial calbes. The digital terminal multiplexes broadband signal components, such as video channels, selected in response to subscriber control signals, with a multiplexed telephony signal and transmits these optically to an active pedestal, and receives the control signals, a multiplexed telephony signal, and optional upstream broadband signal components from the active pedestal. The active pedestal transmits and receives the signals on the first communications path, and demultiplexes the received multiplexed telephony signal and the broadband signal components.

Abstract: Digital samples of an HDTV video signal are compressed by determining groups each of three successive samples in the video signal lines, the groups in adjacent lines being offset from one another, and transmitting only a first sample in each group. Each of the second and third samples in each group is compared with magnitudes averaged from three adjacent, transmitted, first samples, one in each of the previous, same, and following video signal lines, to determine a closest match. A 2-bit code representing this closest match is transmitted for each of these second and third samples in each group. The groups, and hence the first samples, are offset from one another in adjacent video signal lines, and the sampling frequency is desirably an odd multiple of half the video signal line frequency to offset the sampled pixels in adjacent video signal lines. The invention provides a high compression ratio, which can be further increased by DPCM encoding of the successive first samples.

Abstract: A signal distribution system is disclosed for distributing television program signals from a central location to a plurality of subscriber locations via respective optical fibers. At the central location, 4 of 64 signals are selected and multiplexed for delivery to each subscriber location. At each subscriber location, an interface unit selects any 2 of the 4 signals for delivery to each of a plurality of video port controllers, for supply to an associated television receiver and video cassette recorder. Requests for program signals initiated by a subscriber at a video port controller are handled by the interface unit, being granted, denied, or fowarded to the central location as appropriate. The system facilitates the provision of pay-per-channel and pay-per-view television program signals.