Abstract: To convert an input-word sequence into a digital line code of half the bit rate of the input-word sequence, particularly for digital color television signal transmission, an encoder is disclosed which has a difference branch in which the difference (D.sub.i) between every two successive input words (X.sub.i-1, X.sub.i) is converted into a difference code word (D.sub.i) by adaptive PCM quantization, and a sum branch in which the sum (S.sub.i) of the same successive input words (X.sub.i-1, X.sub.i) is converted into a difference code word (S.sub.i +P.sub.i) in a hybrid DPCM encoder. These two words are combined into a line code word (C.sub.i) by an adder (9). The quantizing characteristic of the adaptive PCM quantizer (1) is selected as a function of the prediction error present within the hybrid DPCM encoder (2). The decoder at the receiver of the novel communication system splits up the received line code word (C.sub.i) into the difference code word (D.sub.i) and the sum code word (S.sub.i +P.sub.

Abstract: A time division multiplex system which has a total bandwidth of 64Kbit/s and has this bandwidth split up into 80 channels each of 800 bits/sec. Three speech channels are provided, each using 20 of these channels, 12 channels are used to provide a 9.6Kbit/s data channel, 4 are used to provide for 50-110 baud start-stop channels and another 4 are used to provide a 3.2Kbit/s signalling channel.To provide fast sync, a sync pattern consisting of two sync words and a channel number is sent at the same time on all of the channels, and the receiving side monitors for the 19th channel. When it finds what is coming in at the time, it first achieves bytes alignment between the received byte stream and the local byte stream, then it checks the respective channel numbers. The difference between them gives an offset which is used to adjust the demultiplexing logic.

Abstract: In the rotation rate measuring instrument, a light beam produced by a laser (1) is divided in a beam splitter (4) into two component beams (I.sub.CW, I.sub.CCW) which travel in opposite directions around an optical waveguard (9) forming a closed light path. A Bragg cell (6, 7) is inserted between the beam splitter and each end of the optical waveguide. One of the Bragg cells (6) is driven with a signal (f.sub.VCO) whose frequency is varied in accordance with the rotation rate. For the other Bragg cell, a switch (33) switches periodically between two drive signals (f.sub.MH, f.sub.ML), so that the component beam is frequency-modulated (f.sub.S). A regulating facility (12, 13, 54, 55, 56) is provided which compensates for intensity differences between the two component beams. In further embodiments, it is possible to compensate for those intensity variations of the component beam (I.sub.CW) which are caused by driving the Bragg cell (5) at different frequencies (f.sub.MH, f.sub.ML).

Abstract: A capacitor arrangement which is especially suited for use in an electronically tunable narrow band tuned cavity filter includes two capacitor plate portions which are juxtaposed one another to form a capacitor. One of the capacitor plate portions may be provided with a recess and with an internally threaded bore which opens into the recess, and an externally threaded trimmer slug may be received in the bore and extend to a greater or lesser degree into the recess and thus to contribute to a greater or lesser degree to the total capacitance of the capacitor. A dielectric spacer may be interposed between the capacitor plate portions to determine the size of the gap therebetween and to maintain the gap size constant.

Abstract: The fin-line oscillator includes a packaged diode as an active element and an impedance-matching network for matching the diode to a load and determining the frequency.In a first embodiment, the diode package (5) is mounted in a cutoff waveguide (4) connected with the waveguide (1) containing the fin line. The fins (2) of the fin line extend a given distance into the cutoff waveguide.In further embodiments, the diode package is mounted in or on the substrate on which the fins of the fin line are deposited.

Abstract: An electronic hybrid circuit for coupling a two-wire communication path to a four-wire communication path includes amplifier circuits having a reactive feedback path such that the output impedance of each amplifier is approximately zero ohms at d.c. and is a predetermined value at audio frequencies. The amplifiers are arranged to provide battery and voice signal injection on the two-wire path.

Abstract: A continuous speech recognition system includes a plurality of processors doing template comparisons of speech data. Each processor has an associated memory shared with the other processors by direct memory access (DMA) through a shared data bus. The DMA circuitry is distributed between the processors to eliminate redundancy, since if each processor had a full DMA circuit, one of the circuits would be idle when the processors communicated.

Abstract: A supervisory method for a digital optical submerged transmission system in which a multi-bit test signal is detected by a repeater while receiving a loop-back signal for causing loop-back condition, and the mix of the bits of the test signal is changed to change a d.c. level derived in the repeater from the test signal. This is compared with a local reference level and after comparison a sign change is indicated the loop-back condition is either enabled or disabled and that event is detected enabling the required input or output level of the repeater to be checked.

Abstract: A protection circuit for a push-pull amplifier includes two sensing transistors arranged in respective feedback circuits. The output signals of such sensing transistors, which are indicative of the output voltage, are used to limit the output current of the amplifier in such a manner that the output current is limited to a first threshold decreasing with a steeper slope as a function of the output voltage of the amplifier between predetermined two output voltage values, and a second threshold decreasing with increasing output voltage at a lesser slope above the higher one of the two predetermined output voltage values. This characteristic response can be overridden by appropriate circuitry so long as the temperature of the amplifier is below a predetermined maximum value, so as to make the output current threshold independent of the output voltage.

Abstract: In a handsfree telephone system of the type described in our application No. 584,579, filed in the U.S. on Feb. 29, 1984, the method used to avoid howling due to feedback from the loudspeaker to the microphone is to increase the attenuation to speech in the quiescent direction as compared with that in the active direction. This involves monitoring successive speech samples in the two directions with each sample compared with a preset threshold, which also takes account of the system's noise levels. This is effected under processor control, as in the adjustment of the attenuation, since the system uses digital speech transmission.It has now been found that it is not necessary to monitor all speech samples to derive adequate information about the occupancy conditions of the two speech directions. In the present systems only one speech sample in four is used. This enables one microprocessor to serve two lines alternately.

Abstract: In a power supply consisting of parallel-connected converters, each of the converters includes a current sensor. One terminal of each current sensor is connected to one terminal of each of the other current sensors. The other terminal is connected to the converter's pulse-width modulator through a limiter. If any of the converters fails, the limiter ensures that only a small, limited change occurs in the output voltages of the other converters which is permissible in most cases.

Abstract: An improved cellular mobile radio telephone system is described wherein the switching matrices used to provide communication paths between subscribers is also used to provide paths for carrying control information between a network control and the various transceivers, receivers and transmitters at cell sites. Additionally, statistical multiplexers are provided at the cell sites for multiplexing control signals for many transceivers, receivers and transmitters onto the transmission facilities connecting the cell site with the network control system. At the network control system, apparatus is provided to reformat and packetize control signals from many statistical multiplexers and present the reformatted, packetized information to a network control processor.

Abstract: A two-dimensional acousto-optic deflection arrangement including a source (10a) of electromagnetic radiation, means (18) for modulating the source, means for collimating the output of the source into a beam, and an acousto-optic deflection means (12a) situated in the path of said beam, the deflection means comprising a rectangular body of acousto-optic material provided on two adjacent surfaces with electro-acoustic transducers arranged to launch orthogonal bulk acoustic waves into the material transverse the direction of propagation of radiation through the material whereby the focussed radiation can be scanned in two dimensions over an area illuminated by a source (20) secondary illumination. Typically the scanned area comprises a thermo-optically addressable liquid crystal display device (17).

Abstract: An apparatus for supporting a pipe or similar article includes a bottom skid member which has a relatively flat central bottom surface surrounded by an upwardly extending arcuate surface to form a saucer-like configuration.Positioned on the top of the skid member and above the flat section is an extending cylindrical pedestal member. The pedestal has a central slot into which is inserted a corresponding channel. Various devices can be directly coupled to the channel such as pipe clamps for securing the pipe to the skid and pedestal structure as well as a vertical post which has secured thereto pipe clamping means for supporting the pipe at a given distance above the top surface of the pedestal.

Abstract: In a loudspeaking telephone arrangement, there are separate channels for outgoing speech (A-Tx) and incoming speech (A-Rx), and the channels are sampled at intervals. The results of these samplings, which represent the amplitudes of the speech in those channels are each compared by a microprocessor with a preset threshold. The background noise level is also sampled and the result used to adjust the speech channel threshold. Each channel has an attenuator, and that is adjusted so that attenuation is reduced in the presence of speech and increased in the absence thereof. The adjustment on the basis of background noise enables the current state of the channels to be taken into account.

Abstract: An optical communication system including at a transmitter a semiconductor laser (2) and at a receiver a photodetector (3). Intermediate the transmitter and the receiver is an optical frequency discrimination (4), e.g. a Fabry-Perot resonator. The laser (2) is operated at a substantially constant average power level above the lasing threshold. Superimposed (5) on the substantially constant bias current is a low level modulation signal. The level of modulation of the bias current is sufficient only to cause an effective change in the optical frequency of the laser output without causing the laser oscillations to change from one longitudinal mode to another. The discriminator (4) is tuned to one of the frequencies thus produced.

Abstract: The arrangement comprises N signal channels each responsive to a different one of N signals where N is an integer greater than one. Each of the N signal channels includes a sampling circuit to sample the associated one of the N signals by a different one of N phase clocks with each of the N phase clocks sampling a different one of the N signals at a predetermined different time uniformly spaced over a given time interval. A delay means is coupled to each of the sampling circuits to time align the outputs of each of the sampling circuits so that all sampled signal pulses are time shifted consistent with the associated sampling clock phases. A correlator is coupled to the output of each of the delay means to correlate the samples of the N signals with a reference signal. The output of the correlators are integrated to provide the indication of the time of arrival of the N signals.

Abstract: The arrangement comprises a plurality of correlation means coupled to the received signal with the received signal being clocked into each of the plurality of correlation means by a different one of a plurality of different phased clocks with the different phased clocks occurring at a predetermined different time uniformly spaced over a given time interval and integration means coupled to each of the plurality of correlation means to provide the indication of the time of arrival of the received signals.