Abstract: A synchronous PCM digital transmission system including multilevel multiplexing wherein the higher order multiplexers interleave two or more tributary signals each of which comprises a multiplexed plurality of subtributaries. Multiplexer framing is achieved by means of an auxiliary frame pattern or byte, F.sub.T, which is slidable within the subscriber-defined frames. Each multiplexer in the system re-frames or slides F.sub.T and its associated overhead so that the F.sub.T bytes at each multiplexer are synchronized. The F.sub.T bytes can be used to frame or synchronize scrambling and de-scrambling circuitry. This concept provides multiplexer framing and yields high-speed multiplexed signals which are all exact multiples of the system clock rate, using relatively simple circuitry compared to competitive designs.

Abstract: A dual mode encoding/decoding technique for use in digital systems wherein transmitted digital words are limited, on average, to an alotted number of bits. The transmitted digital words are coded into first and second modes. The first coding mode utilizes predictive differential coding to provide a precision which can be greater than that obtainable by coding information solely with the allotted number of bits, while the second mode assures at least a minimum precision for the allotted number of bits. The first coding mode is transmitted as long as a preselected precision is provided. If not, the second coding mode is transmitted. In the disclosed embodiment, the dual mode encoding/decoding technique is applied to the transmission of color video signals.

Abstract: A status reporting arrangement for a digital transmission system (10) has a plurality of stations (11, 12, 13) in a tandem configuration. Each station (such as 11) includes a reporting circuit (30) arranged for receiving (36) a train of messages (91, 96), each message originating from a different preceding station (such as 13 and 12) in the tandem configuration, followed by a received caboose signal (97). Each reporting circuit responds in turn to the train of messages and the received caboose signal by retransmitting (60) the train of messages (91, 96) but deletes the received caboose signal (97). The reporting circuit, in response to detection of the received caboose signal, appends to the retransmitted train of messages a message (100) from the local station and a new caboose signal (102).

Abstract: A synchronous digital transmission system (12), operating over a prescribed range of bit rates, is interfaced with subscribers (10, 11) whose data sources and receivers have different bit rates by means of transmitter and receiver interface networks (13, 14). The transmitter interface network (13) comprises means (20, 21, 23, 24) for phase-locking an integral subharmonic f.sub.o /N of a variable frequency oscillator (22) to an input clock signal, f.sub.1, associated with an input data stream, and means (25, 27) for encoding the data stream for operation at a bit rate corresponding to the fundamental frequency, f.sub.o, of the local oscillator (22) and including one code violation at a prescribed rate, f.sub.1 /M, related to the input clock frequency f.sub.1. The receiver interface network (14) includes means (30, 31, 32) for decoding the received signal and for recovering the input data stream and clock signal.

Abstract: A system is described for randomly addressing any one of a plurality of remotely located stations connected by means of an electromagnetic wavepath. At the addressing point an addressing signal, comprising a series of m signal bursts, is generated and coupled onto the wavepath (11), where m is an integer and corresponds to the number of stations the addressed station is away from the addressing point. Each remote station includes means (33, 34, 41, 43) for deleting one signal burst and retransmitting the remaining signal bursts. Each station also includes means (34, 38, 42, 43, 44, 50, 51) for recognizing when only a single signal burst is received and for responding in a prescribed manner. By means of such a "count-down" technique, the m.sup.th station from the addressing station is accessed. it is an advantage of such a system that the addressing circuit is the same at all the remote stations.