Abstract: A detector device for detecting the passage of articles of a conveyor comprises an energy source element 8, an energy responsive element 10 and reflector means 27, 9 and 28, positioned so that a beam of energy from the source element 8 to the responsive element 10 first traverses the conveyor path substantially parallel and close to the conveyor surface and is then reflected back and forth across the conveyor path in a plane substantially perpendicular to the conveyor surface.

Abstract: A technique for aligning and coupling dielectric optical waveguides comprises threading the end of a waveguide through the central opening of a triad ball connector and forming by fusion a generally spherical glass bead on the end of the waveguide using, for example, an electric arc. The waveguide is then drawn back so that the bead contacts the balls of the triad connector to accurately locate the waveguide. The bead acts as a locating element and also has beneficial focussing properties.

Abstract: A pair of optical fibres which are to be joined are located with their end portions in coupling elements one of which is transparent to light. The coupling elements are located such that the ends of the fibres are in approximate alignment. Light is transmitted along one fibre so that it is received by the fibre in the transparent coupling element. Light which is not coupled into the core of the fibre is sensed by a sensor and the relative position of the fibres is adjusted until the level of sensed light is a minimum. The sensing of the light is carried out at positions spaced angularly about the waveguide so that an indication of the direction of any misalignment is obtained. The coupling elements are then secured in this position. The adjustment of the fibres can be carried out using a linear translation stage and a microprocessor which controls the stage in accordance with signals from the sensor.

Abstract: A glass suitable for use as the core glass in a high numerical aperture optical fibre has a composition selected from the range of glasses which comprise(i) from 15 to 25 mole percent of soda,(ii) from 25 to 65 mole percent of silica and germania, taken together, the content of germania not exceeding 42 mole percent,(iii) up to 22.5 mole percent of boric oxide and barium oxide, taken together, the content of boric oxide not exceeding 20 mole percent, and the content of barium oxide not exceeding 12 mole percent, and(iv) from 0.01 to 1 weight percent of a redox buffering agent. The glass can be prepared by controlling the partial oxygen pressure of the melt so that it is approximately 10.sup.-5 atmospheres. An optical fibre can be produced, by using a soda-boro-silicate clad glass, and a core glass having the composition in the above range.

Abstract: A data transmission system to enable data to be transmitted along a transmission path at a rate C greater than the upper data rate limit A of the path. A data transmitter driven by an internal clock at C Hertz transmits data along the transmission path and at the same time also transmits a derived clock signal at a frequency C/N Hertz where (C/N)<A along the path. At the receiver the data is clocked into a series of data stores under the control of the transmitted clock signal and is thereafter recombined into a serial stream under the control of the clock signal driving the receiver.

Abstract: A digital switching device of the stored program type operating under the control of a central control unit has a first stage which multiplexes digital signals from a plurality of line units and separates data signals from signalling information. The data signals are fed to an input time switching stage. The input time switching stage operates under the control of the central control unit to transmit signals from an input port in a particular time slot on a highway to an output time switching stage. The output time switching stage transmits the data signals to the first stage which combines them with signalling information and after demultiplexing transmits them to appropriate ports.

Abstract: In order to provide improved resistance to attack by atmospheric water etc. a clad glass optical fibre has a plastic coating which is in turn coated with a metal coating. The metal coating may in turn be coated with a second plastic coating. The metal coating is formed by drawing the plastic coated fibre through a globule of molten metal, the surface of which is exposed to an oxygen rich atmosphere.

Abstract: A wire wrapping tool comprises a head which is formed integrally with a shaft. The head includes a frusto-conical portion which has a chordally extending portion cut away to define a cutting edge. A blade portion is formed on the head, the blade having a slot through which a wire can pass. The head also has an axially extending bore into which a wire wrapping post can be inserted. In use the shaft is attached to a pistol gun to rotate the head. Wire from which the insulation is to be stripped is passed over the edge, through the slot and around a wrapping post. As the wire passes over the edge a longitudinal slit is formed in the insulation which is then stripped away from the conductive core as the wire passes through the slot.

Abstract: A data transmission of the videotex type in which coded information can be transmitted from a central information store to a plurality of terminals. The coded information includes groups of bits representing characters and groups of bits representing control codes. In the transmission technique used in the system a character attribute can be represented by a display control code which is transmitted in association with a cursor backspace code. By using this technique characters of different attributes can be displayed without a space being required between the characters on the display.

Abstract: A duct motor for carrying drawing ropes and the like through cable ducts consists of two inflatable gripper bags and a telescopic section. The duct motor is driven by compressed air, and operates by one gripper bag inflating, telescopic section extending, the other gripper bag inflating and the one gripper bag deflating, telescopic section contracting and the cycle being repeated. Compressed air is distributed within the duct motor by a distribution valve and a pair of inflation and deflation valves associated with each gripper bag. One distribution valve is not located between the gripper bags and this valve has a valve stem which is hollow, and is used for conveying compressed air from an input orifice to the remote end of the duct motor i.e. the other gripper bag.

Abstract: The availability of service in a telephone exchange is evaluated by a technique which includes monitoring for each call type over a period of time the level of usage of the items of equipment required for that call type and evaluating using the monitored data the probability of each particular item not being able to provide a service when required. The probability figures of the call types can be combined to give an index figure indicative of the availability of service of the exchange.

Abstract: Semiconductor compounds which are alloys of group III-V compounds are grown by a liquid phase epitaxy method which includes heating growth apparatus in a reducing atmosphere while maintaining a solvent for the compound, a source of the group III-V compound and another element of the alloy separate from each other. After heating to reduce oxides, the element is added to the solvent, the source is brought into contact with the solvent and the resulting solution is brought into contact with a substrate to effect growth of the compound. Apparatus for carrying out the method is also described.

Abstract: This invention relates to an adaptive demodulator for use in a phase shift keyed microwave communication system. The adaptive demodulator improves the system error rate at a particular carrier to noise ratio by monitoring the output of the demodulator and optimizing the phase offset of the carrier signal recovered in the demodulator to provide a high output. A particular example continuously varies the phase offset of the recovered carrier signal about the highest output value to track variations in the optimum phase offset.

Abstract: A method of enhancing the piezoelectric properties of a polymeric material exhibiting such properties includes the step of exposing the material to a quantity of .gamma. radiation lying within the range of from 1 Mrad to 200 Mrads. The material is subsequently poled. Best results are obtained when the material is exposed to between 1 Mrad and 100 Mrads of radiation. The material treated may be polyvinylidene fluoride.

Abstract: A lightning protector carrier comprises a lamellar element made of electrically insulating material and having a plurality of sets of holes therethrough each set of holes defining a respective socket to receive a respective lightning protector device, and a plurality of electrically conducting terminals for making electrical connection to lightning protector devices at a front face of the element. One hole of each set of holes accomodates a terminal and the terminals are electrically interconnected by one or more busbars at the rear of the element. At least the front surface of the element is shaped such that one hole of each set is separated from another hole of the set by a protruding portion of the element interposed between said one hole and said another hole.

Abstract: An information handling apparatus capable of having a large number of input/output ports includes a plurality of independent processors connected to respective positions around a plurality of closed rings of shifting registers arranged in parallel which form the main storage medium for the apparatus.

Abstract: A rear feed assembly for a microwave aerial, comprising a dielectric support member having an energy reflecting surface positioned against one face thereof. Waveguide means is connected with the support, the center of the waveguide aperture being the phase center of the assembly and the said face of the support being located in the far field region with respect to that center. The support is so shaped that energy emitted from the waveguide means is reflected from the reflecting surface and emerges through a second face of the support with a spherical wavefront centered on the image phase center.

Abstract: An electrical filter network particularly suitable for use at microwave frequencies, comprises a main transmission path and a plurality of pairs of secondary paths interconnected by couplers which divide an incoming signal into components on the several paths and recombine the transmitted components to provide an output signal. Conditions are placed on the electrical lengths of the transmission paths; the magnitude of the frequency-independent components of phase change along the paths and the wave amplitudes in the paths.

Abstract: Data processing equipment suitable for recording details of manually connected telephone calls has a plurality of operator stations with keyboards and VDU's connected in groups to operator's control units which respond to keyed instructions to obtain data from peripheral units storing such data and for recording on magnetic tape cartridge the details of the calls. Each operator's control unit is connected to eight operator stations but is capable of handling inputs from twelve such stations. In the event of breakdown of an operator's control units the eight stations allocated to it are divided into two groups of four which are transferred to the two control units adjacent to that which has broken down. Among the criteria used to determine whether a control unit has broken down are the filling of buffer stores and the failure to perform a particular operation within a predetermined interval of time following the previous performance of that operation.

Abstract: A method of error detection in a digital system in which at least one digit in every n (where n is an integer greater than two) is omitted from use as the "particular digit" in the comparison of succeeding particular digits in a received pattern with the combination in accordance with a predetermined function of at least two digits preceding the particular digit in question by a particular spacing. The pattern is a pseudo-random binary sequence of maximal length and every third digit is taken as the particular digit. Every digit forms part of a comparison whether as "particular digit" or as one of said "at least two digits preceding". Shift registers, means to divide digits between the shift registers, and modulo -2 adders are used to carry out the method.