Abstract: A sequential decoding of a convolutionally encoded sequence has been proposed. Decoding is carried out by extending paths along the branches of code-tree over plural tree levels at a time and calculating likelihood (metric) of the extended paths referring to the received sequence. Decoding is terminated when it proceeds to a node belonging to the last tree level of a data block. Then, one of the extended sequences associated with a node located at the last tree level which has the largest metric is output as a decoded sequence.

Abstract: In a frequency division multiple access (FDMA) communication system, a plurality of carrier frequencies relating to a predetermined frequency band for transmitting a PSK (phase shift keying) signal are provided on a frequency scale. When a service is a low bit rate signal, it is transmitted by using a single carrier frequency and its related frequency band. When a service is a high bit rate signal which can not be transmitted in a single carrier signal, the service signal is divided in to a plurality of low bit rate PSK signals, each of which is transmitted by using a single carrier frequency and the related frequency band.

Abstract: Delay time variation in an optical fiber digital communication system which includes optical regenerative repeaters is measured at one of terminal ends having reference clock signal. A monitor signal which depends upon the delay time variation is provided at the farthest repeater in an area where delay time is subject to secular change by dividing reference clock signal from said terminal end, and said monitor signal is returned to the terminal end from said farthest repeater, and the terminal end compares the returned monitor signal with the divided reference signal by using a phase comparator to provide measure of delay time variation.

Abstract: A cable detector has a plurality of rotatably series connected hooks having an opening mouth for accepting a cable on sea bottom with an equal angular intervals, a contact pressure sensing means for indicating that a cable is engaged with one of said hooks by measuring contact pressure on one of the hooks, and an electrical switch which is actuated by said contact pressure sensing means to provide an electrical signal when a cable is detected.

Abstract: A communication protocol validation system which produces a global state transition chart having a plurality of states and a plurality of transitions between states in electrical form to find an error and/or a deadlock of the protocol has been improved by coupling a plurality of global transitions according to a predetermined algorithm and deleting redundant global transitions. Thus, a number of global states and a number of global transitions in the chart are reduced, and the validation is implemented by using a reasonable amount of hardware in a reasonable time.

Abstract: A self-propelled underwater bed cable burying machine is disclosed, which comprises a bottom running gear body with a high pressure water generator mounted therein and an arm-shaped water jet trenching unit mounted the base end capable of revolution in a horizontal plane on a front portion of the running gear body and having a multiple joint degree of freedom. The arm-shaped water jet trenching unit includes an elbow arm having at least one portion capable of being bent in a vertical plane. The elbow arm having a U-shaped hand provided at the free end for capturing and holding an underwater cable. The U-shaped hand having finger portions each provided at least one cable sensor and a trenching water jet nozzle communicating with the high pressure water generator.

Abstract: A satellite communication among a plurality of small earth stations (very small aperture terminal;VSAT) through a satellite is performed by using a relay earth station which has higher power than a small earth station. A signal goes from an originating small earth station to a destination small earth station, through a satellite, a relay earth station, and a satellite by using two hops propagation. Communication is carried out in digital form. The relay earth station regenerates digital signals from small earth stations. In the process of the regeneration of the digital signals, the error correction technique is applied to reduce the error rate, and a frequency compensation technique is also employed. Thus, a small simple earth station can provide high quality of communication with high C/N. A reference clock signal for operating a small earth station is derived from a reception signal from a satellite.

Abstract: A signal coupler couples more than three transmitter-receivers through optical fiber cables and at least one repeater on a bit-multiplex system, by exchanging or reallocating each time slot according to a transmission station and the related destination. The coupler has a means to release the bit-multiplexing (or demultiplex) the signals from each transmitter by deriving the control clock signals from the information signals themselves. The coupler also has a means for multiplexing the bit signals for each destination by automatically adjusting the phase relationships among the released signals (demultiplexed signals) for bit-synchronization using a delay circuit.

Abstract: An encoding method for facsimile signal which is characterized by encoding data of a line selected out of the all lines of input facsimile signals in a manner of skipping over a predetermined number of lines according to a predetermined encoding method and by encoding the data of one of the thus skipped-over lines from a basic element of higher picture quality contribution judged with reference made to the data of the lines preceding of and/or subsequent to the encoding line which have already been encoded.

Abstract: A time division speech path switch for an electronic exchange system has a plurality of speech path memories for each input highway, and an input highway information is stored simultaneously in all of said speech path memories. The number of said input highway memories is equal to number of output highways, and each speech path memory can store at least one frame information of an input highway. A holding memory is provided at each output highway. A switched output signal is read out of one of said speech path memories according to content of the holding memory coupled with the output highway. According to the invention which has a plurality of input speech path memories and a plurality of holding memories, instead of a single speech path memory and a single holding memory of a prior art, an operational speed of a speech path memory and a holding memory may be slow as compared with that of a prior art. And, a large capacity of exchange system may be designed by using a low speed memory device.

Abstract: In a transmission system, which includes one or more digital repeaters in a transmission line and a digital multiplex/demultiplex branching unit, a code for supervising the digital repeater or repeaters in an in-service state is transmitted according to a data sequence signal obtained through bit-by-bit time-division multiplexing of at least two different kinds of digital signals. The supervisory code has a configuration of a transmission line code obtained by dividing the digital signals into blocks of bits corresponding in number to the sum (n.times.m'+1) of the product of the number n of channels of the digital signals and positive odd number m' and one and adding after each of the blocks a number of parity bits (supervisory bits) corresponding to the respective digital signals equal to the number of the channels, i.e., has a bit configuration of n(m'+1)+1.

Abstract: In an encoder responsive to a sequence of coefficient blocks each of which is composed of a plurality of orthogonal transform coefficients subjected to predictive encoding and orthogonal transform, the coefficient blocks are classified by a classification circuit (55) into a plurality of classes to produce a control signal (CONT) representative of the classes. A quantization unit (60), a code conversion unit (61), and a coefficient selection unit (62, 64) are controlled by the control signal to select quantization characteristics, code conversion characteristics, and coefficient selection characteristics. The quantization unit comprises a plurality of quantizers corresponding to the quantization characteristics while the code conversion unit and the coefficient selection unit comprise a plurality of code converters and a plurality of selection tables corresponding to the code conversion characteristics and the coefficient selection characteristics, respectively.

Abstract: An acoustic surface wave filter bank consisting of a single or a plurality of piezoelectric substrates on which a plurality of acoustic surface wave filters each comprising an input interdigital transducer and an output interdigital transducer are fabricated, wherein center frequencies of adjacently located filters are not adjacent to center frequency of present filter so that leaked acoustic surface waves to the present filter from adjacently located filters are strongly attenuated.

Abstract: A satellite communication system between small earth stations through a satellite and a relay earth station. The relay earth station has a larger antenna and a higher power transmitter than those of a small earth station in order to regenerate received digital signals. The transmission power of the relay earth station is controlled according to rain attenuation between the satellite and the small earth station, and/or rain attenuation between the satellite and the relay earth station, so that rain attenuation is compensated by increasing the transmission power of the relay earth station.

Abstract: The ISDN user-network interface is defined in the CCITT D-channel protocol recommendation (I-400 series recommendations), in which many kinds of communication terminals (e.g. faximile, telephone, teletex, etc.) can communicate through a subscriber line. The user-network interface is improved from the view point of effectiveness of terminal usage, provision of communication service, and, flexibility of system configuration, by providing a control terminal in the subscriber. The control terminal doubles as ordinary terminal equipment, and has a global control function for controlling other subscriber terminal equipment. The control terminal establishes and/or releases a local control phase in which a control terminal controls ordinary terminal equipment in the same subscriber to have them correspond to the communication with another subscriber using the means which belong to the ordinary terminal equipment inherently.

Abstract: An optical repeater for an optical digital transmission line has a pair of in-service monitoring circuits (55, 55') each of which includes a flip-flop (57) for dividing frequency of transmission data to derive commands and burst carrier in the first line (54). A counting means (59, 61) is provided for detecting parity errors and counting the errors in an opposite second line (65). A timing generation means (62) is provided for reading out the counting means (61) upon receipt of the burst carrier. A phase modulator (64) provides phase modulation to a clock pulse in an opposite second line (65) according to the output of the timing generation means (62). The number of errors in the second line (65) is stored in the counting means (61) according to commands in a first line (54) from a terminal transmitter (52). The content of the counting means (61) is forwarded to a terminal receiver (66) through phase modulation of clock pulses in a second line (65) upon receipt of the burst carrier.

Abstract: A communications satellite repeater having input demultiplexers for demultiplexing input beams to a plurality of first channels each having a first bandwidth, switches for interconnecting each input channel to desired output channel on a channel by channel basis, amplifiers, and output multiplexers for multiplexing output channels to output beams is improved by the particular structure of the switch. The present switch (8) has filter banks (9) for providing a plurality of second channels each having a second bandwidth narrower than said first channels by dividing each of said first channels, which can also operate as bandwidth-variable filter banks by multiplexing the adjacent second channels, switches (10) coupled with said filter banks (9) to interconnect said second channels, and multiplexers (11) for multiplexing the second channels at the ouptut of said switches (10) to provide output channels. Thus, each transponder can interconnect a plurality of beams.

Abstract: A movement of a small picture block in a frame of video signals is provided by recursively applying a gradient method to a picture block in a present frame and a preceding frame to provide a series of sub-movements until said sub-movement decreases less than a predetermined value, and the resultant movement is obtained by the sum of the sub-movements. The present invention provides high accuracy in estimation of movement of a block in a picture as compared with a conventional gradient method, and is attractive in hardware implementation.

Abstract: A communication protocol validation system which produces a state transition expansion chart having a plurality of states and a plurality of transitions between states in electrical form to find errors such as an unspecified executable transition, a specified unexecutable transition and a deadlock has been improved by providing new error items of a bounded overflow and an unbounded overflow and deleting redundant transitions. Thus, a number of states and a number of transitions in the chart are reduced, and the validation is implemented by using a reasonable amount of hardware in a reasonable time.

Abstract: In an error correction code decoding system using BCH (Bose-Chaudhuri-Hocquenghem) code for correcting error bits in input data Y=(y.sub.1, y.sub.2, - - - , y.sub.n) having the steps of obtaining syndrome S=(S.sub.1, S.sub.2, - - , S.sub.n) through calculation of YH.sup.t, where H is a parity check matrix, obtaining determinant Q.sub.t (equation 6) which has elements of said syndrome S=(S.sub.1, S.sub.2, - - - , S.sub.n), and Q determinant which is provided by deleting some rows and columns including specified diagonal elements of said Q.sub.