Abstract: A pyroelectric camera tube having a high resistivity target is operated by applying an increasing ramp voltage to the target so as to provide a pedestal potential which permits objects producing a negative change in temperature to be viewed and then pulsing the target to neutralise the resultant electric field established between the signal and electron beam scanned surfaces of the target. Thus during the rising ramp voltage the tube operates in a cathode potential stabilised mode and at the end of the ramp the target is pulsed to operate the tube in an anode potential stabilised mode. Since the pedestal voltage is provided by the ramp voltage the tube may be substantially evacuated.

Abstract: A storage device for a safety belt in which the safety belt is wound up on a shaft rotatably mounted in a housing. A ratchet wheel is carried by the shaft and rotation of the ratchet wheel is arrested by a pawl. The pawl is moved into engagement with the ratchet wheel by an inertia member comprising a ball which, in a normal position of rest, sits on a circular edge of a recess or aperture in a base member. The pawl is of such construction that its tip, which engages with the ratchet wheel, is longitudinally displaceable under a predetermined loading.

Abstract: A within-pulse radar having an array of aerial elements each of which feeds signals to a storage filter via a frequency changing stage, in which the outputs from alternate filters are combined in one channel and the outputs from the remaining filters are combined in another channel which includes a switchable phase shifter which introduces a phase shift of 0.degree. or 180.degree. and which is switched during each pulse length, results in improved separation of scanning and grating lobes. The outputs from the two channels are combined for utilization.

Abstract: A radar system is described in which a transmitter transmits two consecutive pulses only one of which is frequency swept and in which a receiver has two channels, one for non-swept pulses reflected from short range targets and the other for swept pulses from long range targets.

Abstract: The invention is concerned with a bi-phase decoder in which compensation is provided for Doppler shift.In the phase decoder of the invention, the signs and magnitudes of the components of the received signals in the in-phase and quadrature axes are determined and errors caused by Doppler shift are detected by detecting changes in the product of the signs of the two components at times when the magnitude of a predetermined one of the components exceeds that of the other.

Abstract: A marine craft steering assembly comprises a rudder stock mountable on a craft for steering movements; a rudder blade mounted on the stock to partake of steering movements therewith and to swing relatively to the stock to a raised position if the blade encounters an obstruction. The blade is biased to its raised position, and a manually operable device, which may be a tiller, is cooperable with the blade for resisting swinging of the blade lower portion to the raised position and for swinging the blade from its raised position to its lowered position. The stock is releasably pivotally mountable on a craft hull and is locked in mounted position thereon by the aforesaid manually operable device movably mounted on the stock.

Abstract: An early strength hydraulic cement comprising: from 15 to 90 per cent by weight based on the cement, of an orthorhombic or tetragonal phase XC.sub.14 A.sub.5 which is NC.sub.14 A.sub.5 as herein defined or the corresponding phase in which the place of the sodium oxide is at least partly taken by at least one other alkali metal oxide; the balance being predominantly calcium silicates.

Abstract: A navigation aiding system primarily for aircraft consists of a number of spaced apart ground stations. A ranging signal is transmitted to each of a number of aircraft in turn in response to received interrogation signals. The system allows a clock carried by each aircraft to be accurately synchronised with a master clock on the ground to permit the range to be measured precisely.

Abstract: A constant velocity universal joint for transmitting motion between two shafts which are intended to be run at an angle. An even number of spindles preferably equal to, or greater than, four are mounted on a hub member fixed to one of the shafts. Rollers with part-spherical outer rolling surfaces are slidably and rotatably mounted on the spindles and cooperate with corresponding opposed pairs of grooves formed in a cup member fixed to the other shaft. The angle formed between the longitudinal axis of one of the spindles with the axis of its respective shaft being equal to the angle formed between the longitudinal axis of its corresponding pair of opposed grooves and the axis of the latter's respective shaft. This angle between 15.degree. and 45.degree. may differ from one spindle and its pair of opposed grooves to another such unit.

Abstract: A circuit arrangement for recognising two pulses in a series by their mutual separation and indicating the time of arrival of one of the pulses comprising a counter gated by the input signals which counts clock signals until a predetermined reference instant in time, a multiple shaft register which stores the binary count when the counter is inhibited and a serial shift register connected to receive the input signal and having along its length tappings spaced by an interval corresponding to a desired separation between the two input pulses, the tappings being connected to a coincidence gate which provides recognition pulses.

Abstract: A hydraulic control valve for transmitting power from a transmitter to a receiver which is remote from the transmitter. The power is transmitted through an actuating line from the transmitter. The transmitter is in the form of a housing which contains both a pressure relief valve permanently connected to the line and synchronising mechanism for synchronising movement of the transmitter with the receiver.

Abstract: A plug and socket connector is disclosed having releasable locking means to prevent unintentional disconnection. The locking means comprises spring catches preferably formed from flat resilient material and they are fitted in a recess or respective recesses in a shell which forms part of one of the connector portions. An environmental seal is provided by locating the catches in the recess or recesses. Other catches are disclosed which are formed in a solid tubular member.

Abstract: A spool for transporting a fishline comprised of a hub member which has a central opening intended to be received on a spindle of a machine for winding line on the spool and to be received on an eye or guide of a fishing rod when the line is to be transferred to a reel attached to a fishing rod, and an outer annular member which actually carries the line and is received on the hub member. The hub member and the annular member both have a drum and flanges at the ends thereof. When the line is to be wound on the spool the flanges of the members are co-planar with one another and are maintained in place by cooperating ribs on the flanges of the hub member. By exerting an axial force on one of the members, the flanges on the hub member slide along the passage in the hub member drum to a position where a groove is provided, the annular member being able to rotate freely on the hub member at this position for unwinding the line.

Abstract: In a refrigeration system for a substantially enclosed space and including a compressor, a condenser, an evaporator, conduit means connecting the said compressor, condenser and evaporator to form a cooling circuit, and a hot gas by-pass conduit between the compressor and the evaporator, the improvement which comprises means provided in the system for apportioning flow of gas between the cooling circuit and the by-pass conduit so that, during a temperature controlling phase of refrigeration, the gas flows both to the condenser and to the by-pass conduit and the apportioning of flow can cause either net heating or net cooling of the enclosed space.

Abstract: The invention relates to the manufacture of arrays of light emitting diodes (L.E.D.'s) from a wafer consisting of an n-type epitaxial layer on an n.sup.+ substrate. The method includes the steps of forming p-type islands by diffusing a p-type dopant into the epitaxial layer of an n on n.sup.+ wafer, establishing contact with all of the p-type islands by means of a first set of conductors, mounting the wafer on a transparent support with the first set of conductors adjacent the support, depositing a second set of conductors on the n.sup.+ substrate and etching both the substrate and the epitaxial layer from between the conductors of the second set, the two sets of conductors being orthogonal and each p-n junction formed by a p-type island and the epitaxial layer being in contact with one and only one conductor from each set.