Abstract: Each of a transmitter and a receiver connected to an antenna through a duplexer includes a .pi./2 and a .pi. polarizer and an ortho-mode transducer (OMT) serially interconnected. In the receiver the OMT is connected at one output to a branching circuit and at the other output to a coupler which is connected to the branching circuit through a transfer circuit. In the transmitter, the OMT is connected at one input to a branching circuit and at the other input to a coupler subsequently connected to the branching circuit through a transfer circuit.

Abstract: The operational reliability of a light source in an optical communication system has been increased by an improved redundant arrangement of light sources and the switching arrangement of the same. The present light source arrangement comprises a plurality of light sources each of which provides a different wavelength from one another, an electrical switch for actuating the selected one of the light sources, said electrical switch being arranged to replace the actuated light source when there is something wrong with the light source in operation, and an optical multiplexer the input of which is coupled to the outputs of the light sources, and the output of the optical multiplexer is connected to an optical fiber cable.

Abstract: An apparatus for detecting a tone signal in a telephone switching system is provided in which a calculation, in particular, multiplication is performed by a table look-up process in a digital memory, instead of using a conventional complicated multiplier. A tone signal of a particular frequency in a telephone line is detected through a discrete Fourier transform process (DFT), by the calculation of s(i)=x(iT).times.sin(i2.pi.fT), c(i)=x(iT).times.cos(i2.pi.fT), S=.SIGMA.s(i), C=.SIGMA.c(i), and P=S.sup.2 +C.sup.2. In the above calculation, the multiplication (x(iT).times.sin(i2.pi.fT), and x(iT).times.cos(i2.pi.fT)) is performed by a table look up method in a read only memory (ROM). Thus, the calculation is simplified. Further, the ROM has cells for only the discrete particular levels of multiplicands and/or the multipliers to reduce the capacity of the ROM, and the ROM is referred to by the multiplicand and/or the multiplier through the conversion of the same by a coefficient number generator.

Abstract: In a communication system between an exchange station and terminal equipment through an optical fiber cable, a power supply for operating the terminal equipment is supplied from the exchange station through the optical fiber cable in a form of an optical energy. The optical fiber cable is utilized both for transmitting a voice signal between terminal equipment and the exchange station, and for transmitting the power supply from the exchange station to terminal equipment on a time divisional basis. When the terminal equipment is inactive, the exchange station transmits no energy, or transmits intermittently an optical pulse. The duration that the optical pulse is transmitted when the terminal equipment is inactive, is less than 1/10 of the total time.

Abstract: A fault location system for locating the fault point of an optical fiber transmission system has been found. The present system comprises a laser for generating an optical beam, a sweep oscillator for modulating said laser beam, a half mirror mounted between the outlet of the laser and the inlet of the optical fiber to be tested, an optical receiver for converting the optical beam reflected by the fault point to an electrical signal through said half mirror, a modulator for providing the frequency difference between the instantaneous output frequency of said sweep oscillator and the output frequency of said optical receiver, a low pass filter connected to the output of said modulator, and a spectrum analyzer connected to the output of the low pass filter. The present system has the advantage that the S/N of the system is excellent, and plural fault points can be located at the same time.

Abstract: The invention converts between a cyclic and a general code sequence, each sequence having a succession of normal code blocks and an additional or shorter code block. A zero bit series is hypothetically assumed before the additional code block. In an encoder for producing a cyclic code sequence, the zero bit series is placed before the additional code block by cooperation of a timing control circuit and a divider. In a decoder, a counter times an additional cyclic code block and starts counting while another counter is still counting to time a period, which is the period next preceding a normal cyclic code block, whereby the zero bit series is assumed.

Abstract: A cable buried under a sea bottom is located by flowing in the cable an electrical current, and measuring the magnetic flux by said current at four points near the cable.

Abstract: A time division multiplex transmission apparatus which transmits low-speed data and telegraph signals of a maximum of n.times.m channels as high-speed data in a multiplexed manner based on a time division system. The apparatus also separates received high-speed data into low-speed data and telegraph signals.

Abstract: The operation of a laser in an optical repeater in an optical transmission system using an optical fiber cable is telemonitored at a terminal station by changing the mark ratio of the test signal which is transmitted from the terminal station to the circuit.

Abstract: In a telephone switching system having a main-speech-path switch, connected to a plurality of subscribers and a plurality of board trunks, the connection in the main-speech-path switch is controlled as follows. In the first mode, the connection between a calling channel and one of the board trunks and the connection between a called channel and the board trunk are established through the main-path-switch, so as to selectively enable speech between an operator connected to said board trunk and one of a calling subscriber and a called subscriber. In the second mode, the connections between the calling channel and the called channel is directly established in the main-speech-path switch, while simultaneously connecting the two channels to the board trunk through the main-speech-path switch, so as to enable to monitor the speech between the calling subscriber and the called subscriber by the telephone operator.

Abstract: An optical loss in a single mode optical device is measured by utilizing multi-mode equipment. The present system comprises of an optical source (1), a sample (30) to be tested, a reference optical attenuator (31) for replacing the optical loss in the sample (30), a first optical switch (40) provided between the optical source (1) and the sample (30) through a single mode optical fiber, a second optical switch (41) provided between the sample (30) and the light receiver (2) through the multi-mode optical fiber, said reference optical attenuator (31) being provided between the first optical switch (40) and the second optical switch (41) so that the optical path is switched either to the sample (30) or to the reference attenuator (31), the optical fiber between the sample (30) and the second optical switch (41) and the optical fiber connected to the input and the output of the reference attenuator (31) being a multi-mode optical fiber.

Abstract: A digital speech interpolation system is combined with an adaptive differential PCM (ADPCM), employing a speech detector for detecting speech signals and for discriminating voiced and unvoiced sounds. An adaptive quantization bit assignment to the speech is adopted to cope with any freeze-out condition. And further PCM speech signals with 8 KHz sampling are applied to ADPCM after shifted 250 Hz down and then converted into 6 KHz sampling frequency, thereby attaining a total gain of about 7 without degrading speech quality.

Abstract: In a digitalized facsimile transmission system, (k) number of scanning lines (k=2 or 4) are encoded to a relative address code and the next scanning line is encoded to a run length code, and each scanning line has the related synchronization code pattern corresponding either said relative address code or said run length code. Thus, the effect of a transmission error is restricted within one scanning line when that error occurs in the scanning line encoded to run length code, or k lines when that error occurs in the scanning line encoded to relative address code. The value (k) is switched between k=2 and k=4 according to the instantaneous quality of a communication line. When the quality is good, k=4 is selected, and when the quality is bad, k=2 is selected. The reception side can switch the decoding systems between relative address decode and run length decode, by being controlled through the related synchronization code patterns.

Abstract: In a sampling function type equalizer having a transversal filter with a plurality of potentiometers, the tap weights of the transversal filter are adjusted according to the desired values of the amplitude-frequency characteristics A.sub.p (n), and the delay-frequency characteristics .tau..sub.p (n). The first multiplication of A.sub.p (n) and the predetermined discrete function in addition to the second multiplication of said .tau..sub.p (n) and said predetermined discrete function, are performed. Also, the Bessel function is provided according to the product of the second multiplication. The first convolution integration is performed for the product of the first multiplication, the second convolution integration is performed for the output of the Bessel function, and the third convolution integration is performed between the results of said first and the second convolution integrations. The result of the third convolution integration provides the tap weights of the potentiometers of the transversal filter.

Abstract: A smear filter and/or a de-smear filter having the characteristics that the delay time is proportional to the frequency comprising (a) a transversal filter having a plurality of delay elements connected in series with one another, the delay time (T) of each delay element being the same as the sampling interval of the input signal, the first delay element being connected to the input terminal, a plurality of potentiometers each connected to the junction points of said delay elements and the output of the last delay element providing the tap weight to each of the tap output, and an adder for providing the sum of the outputs of said potentiometers to provide an output of the present delay circuit, (b) a digital memory storing the precalculated value for each desired delay characteristics for providing the tap weights of said potentiometers, and (c) means for providing the content of said digital memory selectively to the potentiometers according to the desired delay characteristics.

Abstract: The present invention relates to a non-linearity compensating circuit for high-frequency amplifiers comprising a branch coupler for dividing the input signal into two components, two high-frequency amplifiers, one operating in the non-linear region, the other operating in the linear region, and each receiving one of the two signal components from said branch coupler, and a signal synthesizing circuit for taking the vectorial sum of the two antiphase signals from the two amplifiers whereby the non-linearity compensating circuit provides an input/output characteristics which is just the opposite of the input/output characteristics of the high-frequency amplifier to be compensated. Basically, the non-linearity compensating circuit according to the present invention does not require long delay lines, variable attenuators or variable phase-shifters of a special design so that the whole circuit can be constructed in a microwave integrated circuit form which has a reduced power loss.

Abstract: A cable detecting system with a cable ship, a cable detector towed by said cable ship via a towing wire and said cable detector dredging the water bottom to find a buried cable, has been improved. When the cable detector detects a buried cable, and the cable is engaged with the cable detector, the towing wire between the cable ship and the cable detector is released either by drawing out a wire from the cable ship or by extending an auxiliary wire from the cable detector, thus, the cable detector stops just when a cable is detected, even when the cable ship continues to move by inertia, and no damage is caused to the cable. The presence of a cable is sensed either through a mechanical means which detects the cable by contact between the cable and the detector, or through electromagnetic means. The detection of a cable triggers the above release of the towing wire.

Abstract: The error rate and the operation of repeaters inserted in an optical transmission line are monitored at the terminal station on land by transmitting the test signal and monitoring the response signal of repeaters through the optical data transmission line without utilizing interstitial copper pair. Each repeater has the particular identification code, and the transmission terminal transmits the test code having the repeater identification code and an acknowledgement block with an empty bit position on the time divisional basis with the data to be transmitted. The repeater which finds his identification code in the test code, inserts the response in the acknowledgement block, and repeats the signal including both said test code and the data to be transmitted. The reception terminal analyzes the response signal of each repeater to determine the error rate of each repeaters.

Abstract: According to the present editing printer, a printing head can print either on the first insertion line or on the second ordinary line by the operation of a keyboard, and the characters from the keyboard are also stored in a memory. An insertion end sign " " is printed at the end of the insertion characters on the first line. A group of characters from the first character to the character before the insertion end sign on the first line are inserted automatically in the second ordinary line by the aid of the memory, which provides clean output with no error after editing.

Abstract: An apparatus for reducing a sampling frequency which derives information with the bandwidth f.sub.B /N (N is an integer) having a sampling frequency of 2f.sub.B /N from an input FDM signal with a bandwidth up to f.sub.B having the sampling frequency 2f.sub.B has been found. The present apparatus comprises a pair of partial frequency reduction systems and a switch for alternately selecting the outputs of said partial frequency reduction systems to provide the output signal.