Abstract: Measurement apparatus receives a signal from an eddy current transducer (20) excited by a generator (24). A signal generator (21) generates a signal at a predeterminable reference level which is combined with the transducer signal to produce a measurable signal at output (23). The output of the signal generator (12 ) is determined by a set balance control (15) which may be set by amplitude controls (29,30) in accordance with control coefficients applied via data bus 43. The output of the signal generator (21) may be predetermined iteratively in a calibration phase preceeding measurement. The present invention overcomes the problem of providing an inactive matched eddy current transducer to balance the signal provided by the measurement transducer (20). A second transducer (49) may be switched (50) to replace the signal generator (21) to enable positioning of the measurement transducer (20) with respect to a workpiece.

Abstract: A method in which a phosphor film of manganese doped zinc chalcogenide is produced by chemical vapor deposition from alkyl zinc vapor and the gaseous hydride of the chalcogen. The manganese dopant is introduced uniformly during deposition by decomposition of tricarbonyl alkylcyclopentadienyl manganese: ##STR1## where here R denotes the alkyl radical. Preferably dimethyl zinc and tricarbonyl methylcyclopentadienyl manganese are used.The phosphor produced may be one of the following manganese doped compounds: zinc sulphide, zinc selenide, zinc sulphur selenide, zinc oxy-sulphide, zinc oxy-selenide or zinc cadmium sulphide.

Abstract: A photo diode formed by a substrate of Cd.sub.x Hg.sub.1-x Te covered with a layer of CdTe forming a p-n junction. The substrate may be p-type in which case the layer is n-type or vice versa. An array of photo diodes may be formed by covering the substrate with semi-insulating CdTe and forming islets of In on the CdTe. Heating causes In to diffuse into the CdTe doping it n-type. This results in regions of n-type CdTe surrounded by semi-insulating CdTe each region forming, with the substrate, a photo diode. The heating also causes diffusion between the Cd.sub.x Hg.sub.1-x Te and CdTe to give a graded heterostructure. Electrical connections are made to the substrate, and each n-type region. The n-type CdTe region may alternatively be formed by molecular beam epitaxial growth techniques using a beam of In dopant.

Abstract: A material suitable for thermosetting includes a collection of hollow particles adhesively mixed with a thermosetting resin in such proportions that the mixture exists in a granular form and may be converted by thermosetting into a fused solid mass having a density not greater than 0.5 grams per cubic centimeter.The particles may be glass microbubbles or phenolic microballoons and the resin may be a hardenable Friedel-Crafts resin. The material according to the invention is more suitable for packing into shaped cavities than known resins including those containing filler particles.

Abstract: The invention relates to underwater acoustic devices and arrays formed from such devices, and which in use are suspended in water from a buoy as other flotation equipment. An underwater device in accordance with the invention comprises an elongate tubular structure which is preferably suspended from a buoy having an aerial mounted on the buoy and connected to a radio transceiver housed within the buoy, wherein the tubular structure includes a plurality of transducer elements spaced apart along a common axis, preferably by spacer tubers wherein each of the transducer elements comprises a tube, or part of a tube, composed of a piezoelectric material, preferably polyvinylidene fluoride, and electrical terminal means contacting inner and outer curved surfaces of each tubular element.

Abstract: A material suitable for a guest-host liquid crystal device comprises a solution of a liquid crystal material and a pleochroic dye wherein the pleochroic dye comprises at least one compound having a formula: ##STR1## wherein one of X and Y is OH and the other is NHR wherein R is H or lower alkyl; each of R.sub.1 and R.sub.2 independently represents alkyl, aryl, aralkyl, alkoxy or --NR.sub.3 R.sub.4 wherein each of R.sub.3 and R.sub.4 is independently H or lower alkyl, provided that R.sub.2 is always adjacent to an OH group.

Abstract: An intruder detection system wherein light pulses are fed from a light source to a detector via a transmitting optical fibre, an optical terminator and a receiving optical fibre, both fibres being either stepped index fibres or poor quality graded index fibres. The fibres are disposed in intimate contact throughout their length within a cable, and compression of the cable at any region of its length sufficient to cause microbending permits light pulses to breakthrough from one fibre to the other. The time interval between arrival at the detector of a light pulse received from the source after passage through the total length of the transmitting fibre and the receiving fibre, and arrival of a breakthrough pulse received after passage through the fibres only so far as the region of microbending and back again, is indicative of the location of the compresion. The cable may be laid around the perimeter of a site to be guarded so that compression will occur when an intruder crosses the cable.

Abstract: A self-loading firearm for firing rubber bullets and the like has an actuating mechanism comprising a toggle linkage which is straightened on operation of the trigger against its spring bias. Initial straightening of the toggle linkage moves the breech block forward to locate a round of ammunition in a short socket at the chamber end of the barrel. As the toggle linkage moves over center it locks the breech block forward and displaces a sear to release the firing pin. The round is fired with its case virtually unsupported. On release of the trigger the toggle mechanism is bent so withdrawing the breech block and the spent round which is automatically ejected. The firing pin is simultaneously re-cocked. Rotary and vertical stacking rechargeable magazines are described, from which a fresh round is automatically fed to the breech on ejection of a spent round.

Abstract: An electrothermal gas thrust unit for a space vehicle has a thrust chamber with an extension tube extending upstream therefrom. An injector tube leads into the extension tube and a diaphragm contacting the extension tube adjacent its juncture with the injection tube conducts heat away from that juncture to maintain the local temperature at a level below that at which liquid fuel (such as hydrazine) vaporizes.

Abstract: High strength, high modulus reinforcement fibres having a greatest cross-sectional dimension of about 100 .mu.m or less and suitable for setting in a matrix material, e.g. resin, are characterized by a cross-sectional shape which is or approximates to a flat-sided polygon of three or more sides, preferably three sides.

Abstract: The invention provides circuit matching elements primarily for integrated circuits and particularly for monolithic microwave integrated circuits.A transmission line in accordance with the invention is provided with a thin metallic film deposition disposed in the signal propagation path. The effect of the film is to increase the specific capacitance of the line without decreasing the specific inductance. The result is a slowing down and therefore a decrease of the wavelength of signals in the line.An example of an implementation of the invention is a coplanar waveguide having a central thick conducting line element (32) and outer thick conducting line elements (28,30) mounted on a substrate (21). The central element overlies a thin metallic film (22) which also underlies the outer conducting line elements and is insulated from the latter by polyamide insulation (24,26).

Abstract: A liquid crystal display comprises two transparent slides containing a thin layer of liquid crystal material which may be nematic or cholesteric. Addressing electrode structures on the inner faces of the slide allow voltages to be applied across the layer to cause an observable display effect. The voltage at which an observable display occurs is temperature dependent. Sensing electrodes are connected in series with a reference impedance (Z.sub.f). With a constant supply voltage (V.sub.o) across the sensing electrodes and reference impedance (Z.sub.f) the voltage (V.sub.LC) variation is used to control the voltages applied to the addressing electrode to compensate for temperature variations in the layer.

Abstract: Stripline antenna arrays of the type in which the strip turns through successive right-angle corners to form successive four-cornered cells, the lengths of the longitudinal and tranverse strip sections being such that the summed radiation in each cell has the same polarization direction, viz vertical, horizontal or circular, radiating in the broadside direction effect arbitrary polarization directions radiating in any direction in the plane (x-z) normal to the array which contains the array axis, by using cells having six potential right-angle corner sites and strip sections of appropriate lengths. The number of actual corners may reduce to four; e.g. where strip-section lengths reduce to zero.

Abstract: In a prior form of stripline antenna, the strip turns through successive right-angle corners to form successive multi-cornered cells in which the lengths of the longitudinal and transverse strip sections are such that the summed radiation from each cell radiates in the same direction and with the same polarization direction. In the present disclosure, the distribution of radiated power along the array is varied, e.g. to maximize it at the center, by varying the absolute lengths of these strip sections as between cells while maintaining their required relationships, e.g. by progressively increasing these lengths towards the center of the array in order to increase the radiated power accordingly. This compares with the previously known method, viz varying the strip width.

Abstract: A protractor for determining the elevation angle of a gun by direct measurement of the included angle between a first radius of a trunnionand a second radius of an associated trunnion bearing, includes a linearly extensible measuring device with digital output, pivotally attached to the trunnion and to the bearing at predetermined distances along the respective radii so as to extend between them as the subtense of the included angle, and a digital processor for deriving a measurement of the included angle from the subtense measurement provided by the measuring device. The digital processor provides an output which is particularly suitable for application to a fire control system, the measurements provided by the protractor being less sensitive to centering inaccuracies in the trunnion and its bearing than conventional angle transducers operating at a subsidiary bearing.

Abstract: A round of ammunition for use in training comprises a standard brass cartridge case (1) containing a reduced propellant charge (14) and a bullet (2) of standard shape comprising a core (3) of rigid polyurethane foam and an external skin (14) of unfoamed polyurethane. The core and skin can be moulded integrally. The round is designed for firing in an automatic weapon and actuating its automatic mechanism. The skin of the bullet should be not less than 0.02 mm thick to withstand handling, and not more than 0.10 mm thick to avoid production of large fragments thereof on firing. The bullet can have opposite ends both of ogival form to facilitate manufacture and operation. The round is mainly for small arms up to 10 mm caliber.

Abstract: A method for producing a MISFET having a gate electrode formed at the base of a grooved recess. The grooved recess is formed with steep side-walls (e.g., be reactive ion etching, ion beam milling or by using an orientation dependent etchant) and gate and source and drain contacts are formed by the simultaneous deposition of conductive material (e.g., metal evaporated from a point source.) Steepness of the side-walls of the recess ensures separation of the conductive material, isolating the gate electrode from the remaining conductive material providing the source and drain contacts.A silicon MISFET may be produced, using a diazine catalyzed ethylenediamine-pyrocatechol-water solution etchant, and exposing the (110) crystal plane face of the silicon to the etchant to form the recess.

Abstract: A pallet for use in decking a bridge constructed from girder sections of the type disclosed in Patent No. GB 1209747 comprises a plurality of decking units (1) held in pre-determined disposition by tie bars (7) and spacers (6) so as to engage directly with corresponding recesses (4) in the girder sections (5). The pallet is provided with slinging eyes (9) and may be used to carry additional decking units for manual distribution along the girder sections.

Abstract: A firearm especially for firing large calibre rounds such as rubber bullets and having a rotary magazine which is rechargeable at any stage of depletion. A loading arm serves to guide rounds through an inlet opening in the magazine, in such a way that they are received into corresponding locations in a rotating carrier, and the carrier rotates forward one position with each additional round. Until the penultimate round, the guide means is locked to the magazine body. In this position, it obstructs further movement of the first-inserted round and thus prevents insertion of the final round. Mechanism is described by which, on insertion of the final round the guide means automatically unlocks from the magazine body and locks to the rotating carrier. In this condition it serves to keep the first inserted round locked in the magazine as it completes a full rotation to come opposite the inlet opening once more.

Abstract: Novel liquid crystal compounds are disclosed, which are chiral esters based upon the phenol ##STR1## Typical examples are: ##STR2## and mixtures of these compounds have a helical pitch such that the mixtures reflect light of a specific wavelength when illuminated with ordinary light and the pitch is temperature sensitive so that the mixtures can be used in temperature indicating devices. Specific examples are given as are samples of mixtures that can be used in phase change electro-optic display devices.