Abstract: Waveguide switching apparatus includes a stator and a rotor arranged to rotate relative to it. The rotor includes passages therethrough arranged to make connections between channels in the stator depending on the relative position of the rotor and stator. One passage is defined partly by the rotor and partly by the stator. This reduces the inertia of the rotor compared with a conventional switch in which all passages are entirely contained within the rotor, and thus improves switching accuracy. A passage in the rotor may have a dimension, in a plane transverse to the axis of rotation, which varies along its length, being smallest at its mid-length. Curved passages in the rotor may be arranged such that tangents to their center lines at their ports are non-radial. This enables the diameter of the rotor to be smaller than would otherwise be required. In another aspect of the invention, an asymmetric circumferential slot arrangment is included in the rotor.

Abstract: A method of improving the electrical characteristics of a thin film (1 or 9) formed on a substrate (3 or 11) by a Langmuir-Blodgett process. The method comprises immersing the film (1 or 9) in a fluid (5 or 13) and applying an electrical potential to the substrate (1 or 9) such that a self limiting electrochemical reaction within the fluid (5 or 13) causes any voids in the film (1 or 9) to be preferentially filled.

Abstract: A differential relay includes two apparatus each associated with a different monitoring point on the line being protected by the relay. Each apparatus includes means for deriving digital data representative of the current monitored at the respective point, at time intervals defined by a clock within the apparatus. The two points are linked by a digital data communication channel, and information transmitted between the two points is used to compute digital data for the two points at substantially the same time, from digital data derived at different instants at the two points.

Abstract: A frame transfer buried channel CCD image sensor incorporating an anti-blooming drain structure (25, 27) wherein accumulation of charge of opposite polarity to that drained by the anti-blooming drain structure is prevented. This can conveniently be achieved by arranging for the buried channel diffusion (19) in each channel to stop short of the anti-blooming drain diffusion (25) on one side of each channel. As a result of the prevention of charge accumulation the anti-blooming drain structure remains effective with optical overloads much greater than the optical overload at which anti-blooming performance begins to deteriorate in conventional buried channel CCD image sensors.

Abstract: A grinding device for grinding the ends of fibres and particularly optical fibres comprises a stand 10 carrying a mounting arrangement 13 for mounting a fibre and rotating it about its longitudinal axis. The stand 10 also carries a grinding wheel 18 and a microscope 22. The positions of the microscope 22 and mounting arrangement are all accurately controllable by micrometers 12, 23, 25 and 27.

Abstract: In a frame transfer CCD image sensor the number of charge storage locations per channel (25) in the store section (35A, B) is greater than in the image section (33). Frame transfer is effected so that after each frame transfer the image charge pattern in the image section is transferred to the store section so as to leave at least one line of charge storage locations (35B) in the store section between the image section and the charge pattern transferred to the store section which contains charge resulting only from frame shift smear and is otherwise empty of charge. Electrical circuitry (41 to 57) is provided to subtract electrical signals representing charges in the line or lines containing frame shift smear charge only from electrical signals representing the image charge pattern, thereby to cancel frame shift smear in the signals representing the image charge pattern.

Abstract: Optical couplers, whether in integrated or fibre optics, where there is at least one input lightpath coupled to two or more output lightpaths by depositing a film of resistive metal over the coupling region and passing current through the film. This heats up the coupler and thus increases the refractive index forming a preferential light path through the heat region. Thus by heating particular regions, and by varying current through the film, the coupler is tuned as desired.

Abstract: The invention concerns an electronic ringing circuit for telephone systems. A capacitor is connected to the center tapping of a first coil inductively coupled to a transistor-controlled supply line. The other side of the capacitor is connected to the junction between two switches each switch being connected via an induction coil to one end of the first coil so that when the switches are switched in opposite senses load current is drawn in alternate directions from the capacitor.

Abstract: A surface acoustic wave filter comprising; a first bidirectional ID transducer (5) of symmetrical form; a second ID transducer (1) acoustically coupled with the first transducer and comprising two parts (1A, 1B) each of which parts is in the form of one half of a respective bidirectional ID transducer (9 or 11) of symmetrical form, the two parts being positioned with respect to one another and the first transducer so that when respectively excited by corresponding signals of different phases they co-operate to produce a unidirectional acoustic signal propagating towards the first transducer from one side thereof; and a third transducer (3) acoustically coupled with the first transducer and comprising two parts (3A, 3B ), each of which parts is electrically connected in parallel with a respective one of the two parts of said second transducer, and each of which parts of the third transducer is effectively in the form of the mirror image about the center line (7) of the first transducer of the other half of the

Abstract: A method of fabricating a generally planar device such as a lead frame, having fragile portions contiguous respectively with relatively robust portions, which includes in sequence, the steps of providing a robust, generally sheet-like blank, removing material from selective portions of a surface layer of the blank at one of its main surfaces to define first portions of the surface layer to be the relatively robust portions in the finished device and second portions to be fragile portions of the finished device, firmly embedding the second portions in a fixing material layer, and removing material from the other main surface of the blank in the region of the embedded portions to a sufficient depth to expose an underside of the surface layer, thereby to isolate the embedded portions from each other and to render them thinner and thus more fragile than the first portions.

Abstract: Bed-of-nails test access jigs are commonly used to effect the required electrical connections between an electronic circuit constructed on a printed circuit board (PCB) and the automatic (electrical) test equipment (ATE) used to carry out their testing. "Fixed" bed-of-nails jigs have a number of disadvantages that can be overcome by the use of a programmable bed-of-nails jig, but the present-day programmable systems using apertured masks, or secondary pin frames, to set up a particular pin configuration, do not provide a good solution where the pin configuration has to be changed during the testing sequence. The invention suggests a design employing individually-controlled pin control mechanisms such that from a total field of pins individual pins can be programmed to make contact with the PCB. It enables the pin actuating mechanism to fit into the space available by proposing the use of miniature clutch, or valve, mechanisms involving the utilization of an electro rheological fluid.

Abstract: An electricity metering equipment wherein, in order to reduce the possibility of fraudulent consumption of electricity, there is provided in addition to the usual meter (3) for measuring the amount of electricity consumed in a load, an independent device (5) which produces a signal representative of the current supplied to the load. A comparison device (4) then compares the signal with the rate of electricity consumption measured by the meter, and an output signal is produced if there is a discrepancy which may be used to disconnect the supply and/or transmit a signal to the supply authority.

Abstract: A vehicle control and guidance system in which a desired route for the vehicle is stored in the vehicle in the form of co-ordinates in a ground reference frame. The `vectors` between these junction points are divided by successive reference points into incremental vectors, the reference points being generated ahead of the vehicle at regular intervals. A dead reckoning system predicts the position of the vehicle at the end of each interval and this estimate is corrected, using a Kalman filter, by an independent fixed-target detection system using a scanning laser. The error between the estimated vehicle position and the local incremental vector provides a steering angle correction for the vehicle and the vehicle speed is dependent upon the lag of the vehicle behind the generation of reference points.

Abstract: The 16 kbit/s HDLC formatted signalling channel for each of 256 ISDN subscribers is separated from the data channel(s) at the exchange line circuit and TMD multiplexed into a 4 Mbit/s stream provided to a common signalling handler. In the handler, a receiving element processes each new bit of the 4 Mbit/s stream with 47 bits read out of a channel parameter store by a channel number provided by a channel allocation store. The 47 bits include the previous 7 received bits and a message byte address for that channel. When those 7 bits and the new bit form a new deformatted message byte, that byte is written into an incoming message store at a location determined by the current channel number and message byte address. Using a FIFO buffer, messages are read from the incoming message store by a processor in the order in which they are completed.

Abstract: A Mach Zehnder interferometer with arms of equal length is formed between two optic fibres. This is achieved by locating the lightly tensioned fibres in a generally parallel configuration and forming optical couplings between them at points which lie on the center-line of the configuration. Preferably the couplings are formed by a fused biconical tapering technique.

Abstract: It is often required to solder an electrical connection to a component or a lead thereto via a contact pad. At present pads are commonly of materials that tend to oxidize during any subsequent heat processing of the device, and are then difficult to solder. It has now been discovered that certain alloys of copper containing manganese may be used to construct contact pads that are both solderable and remain so even when ovened in air at 200.degree. C., and the invention provides a method of constructing solderable contact pads upon a chosen substrate, in which method there is formed on the relevant area of the substrate a layer of such a manganese/copper alloy.

Abstract: An active matrix addressed liquid crystal display is described, each liquid crystal cell within the display having two electrodes each carried on a surface of a different one of two insulating plates. Each cell is connected via a respective transistor to a pair of address lines each address line within a pair being connected to different cells within the array, and each line within a pair being carried on a different plate. Synchronized electrical pulses are applied to the address lines to switch on selected cells within the array, the sense of the pulses on one of the lines being periodically changed.

Abstract: This invention relates to rotatable antenna feed polarizers for use in communication antenna systems, and seeks to provide, at economic cost, an antenna feed polarizer which is capable of being rotated accurately.The polarizer is rotated by a threaded member rotated by a motor. A drive member is moved longitudinally by the rotation of the threaded member. Two flexible connectors are each attached at one end to the drive member, pass around idler wheels, are wrapped partly around the polarizer, and are fixed to the latter. Movement of the drive member pulls one of the flexible connectors and thereby rotates the polarizer.Backlash is minimal because it occurs between only two moving parts, the drive member and the elongate member, and is achieved without using gears with minimum backlash, which may be expensive.

Abstract: A distance relay, for indicating single phase to ground faults on a polyphase electric power transmission system, having guard zone comparators (17,18,19) generating a first guard zone quadrilateral characteristic (21,23,25,27) in respect of each phase of the system and additional comparators (43,45,47) cooperating with the guard zone comparators (17,18,19) for generating a second main quadrilateral characteristic (23,25,27,49) in respect of each phase of the system, and a logic circuit arrangement (31 to 41) whereby the relay indicates the presence of a fault on a single phase to ground within the reach of the main characteristic relating to the relevant phase only if the corresponding guard zone characteristic, and no other, indicates a fault. The slope of the reactance line (21) of each guard zone characteristic is arranged to change its slope under two-phase phase to earth fault conditions by a lesser amount than the reactance line (49) of the corresponding main characteristic.