Abstract: A phase detector for producing an output signal indicative of the relative phase of periodic transitions in a first signal and a further periodic signal comprising: a smoothing circuit (33); a variable gain amplifier (31) via which the first signal is applied to the smoothing circuit; and a control circuit (35) for varying the gain of the amplifier cyclically between positive and negative values at the frequency of the further signal.The detector finds particular application in a phase locked loop arrangement whereby a periodic signal generator is phase locked to periodic transitions occuring between an adjacent pair of channels in each frame of a multiplex time division signal, the other frames of which contain analogue data. The gain of the amplifier is then suitably varied in steps of equal magnitude between positive and negative values of equal magnitude, the time between adjacent steps being equal and the number of steps being equal to the number of channels in a frame.

Abstract: A radar system for tracking airborne targets, in which the transmitted pulse signal is swept over a predetermined frequency range (3). A local oscillator (15) in the receiver is swept over a similar frequency range the L.O. sweep modulation being initiated (20) by the first significant target return signal. Reflectors on the target at different ranges therefore produce different I.F.s in the receiver. Discrimination between the various target reflector features is thus achieved by filtering (25, 27, 29) the I.F. signals in a series of small bands, each band corresponding to a particular target-feature range. Azimuth, elevation and magnitude of a target feature can thus be obtained for each range cell.

Abstract: A data memory arrangement includes n columns of storage elements each column being addressable only one element at a time and having at least n.sup.2 storage elements so as to provide a succession of square arrays. Each square array comprises square sub-sections. On storage of a complementary array of data the data is multiplexed from each square array to the next within each sub-section and after each cycle of such multiplexing the sub-sections are rotated one step cyclically. Such rearrangement of data gives freedom and speed of simultaneous access to data words occurring in original rows and/or columns without excessive penalty in the complexity of the addressing system.

Abstract: A display system including a display device, a storage means having an array of storage locations each location being adapted to contain data representing a visual parameter of a different pixel of a picture to be displayed, and signal generating means for causing the display device to use the data to display a picture. the storage means is adapted to store data relating to a picture of a larger area than the picture displayed at any one time, the generating means incorporating means for altering the locations in the storage means which are addressed to produce the picture displayed in dependence on the required portion of the larger area picture which it is required to display.

Abstract: A radar scanner unit for an airborne early warning system comprises an aerodynamic radome pod (1) pivotally mounted on a pylon (2) which is in turn pivotally mounted on a framework (19). The pod (1) can be retracted towards the framework (19) and the unit can be bodily fitted via a standard cargo loading aperture into the fuselage of an aircraft. In flight, the pod (1) can be deployed from and retracted into the aircraft fuselage via the cargo-loading aperture, doors (3) being arranged to fit round the pylon (2) when the pod (1) is deployed.

Abstract: An inductive coupler system suitable for subsea use. The coupler has two sub-assemblies (17, 65) each including a magnetic half-core (35a, b). A tubular guide arrangement (18) is provided into which the first sub-assembly (17) is able to slide. The guide arrangement (18) includes means (63a, 63b) capable of co-acting with means (25a, 25b) fixed to the first coupler sub-assembly (17) so as to constrain the first coupler sub-assembly to take up a position within the guide arrangement to receive the second coupler sub-assembly (65) via an aperture (59) in the wall of the guide arrangement.

Abstract: A strapped-down intertial system for a vehicle including computational means and a sensor package. The sensor package includes a first part (1) fixedly mounted on the vehicle, and a second part (5) which is rotatable about a first axis (Z). On the second part (5) are fixedly mounted gyroscopic means (13, 15) responsive to rotation about two axes, one of which is the first axis (Z), and accelerometer means (9, 11) responsive to acceleration along two axes, one of which is not the same as either of the two axes of the gyroscopic means (13, 15). The computational means is arranged to calculate the heading of the vehicle from the outputs of the gyroscopic means and accelerometer means taken with the first part (1) stationary, and the second part (5) successively in at least three different angular positions about the first axis (Z).

Abstract: A helmet mounted night vision viewing system comprising a goggle arrangement supported from above the face aperture of the helmet, the goggle comprising two independent viewing arrangements, one for each eye of a wearer of the helmet, each viewing arrangement comprising an optical projector (11, 13, 15) arranged to project an intensified image of a scene ahead of the helmet wearer downwardly to an eyepiece (17) in the form of a body of refractive material (20) in front of the wearer's eye wherein light from the optical projector is reflected at an aft surface (23), towards a curved reflective surface (25) from which the light is reflected back towards the aft surface for transmission therethrough to the wearer's eye.

Abstract: A two-part separable inductive coupler is provided in one part with a current-limiting reactor whose control winding is energized by control means in response to the formation of a magnetic circuit between primary and secondary windings incorporated in said one part and the other said part respectively. Said control means may comprise a rectifier connected across said primary winding and is arranged to saturate the reactor when the coupler parts are connected and leave the reactor unsaturated when the parts are separated, so as to limit the primary current.

Abstract: A clamp arrangement for clamping a marginal portion of a board between two opposed substantially flat parallel walls. The mechanism is mounted on the board and is arranged to be capable of expansion in a direction normal to the board. The mechanism comprises an elongate spring strip extending in the direction of its length along the marginal portion, and having corrugations transverse to its length. An elongate cam overlies the spring strip, the cam having a plurality of cam surfaces along its length spaced apart at the same pitch as the spring strip corrugations. Clamping is obtained by sliding the cam relative to the spring strip bringing the cam surfaces into contact with the corrugations, thus causing expansion of the mechanism and subsequent pressure on the two opposed walls due to compression of the spring corrugations.

Abstract: An inductive coupler system including a first part in which is defined a socket region and a second part including a plug member. A first frame member carrying a first magnetic half-core constituting one half of an inductive coupler is supported by the first part, while the second part carries a second magnetic half-core constituting the other half of the inductive coupler. The first part includes actuation means responsive to the insertion of said plug member in said socket region to move the first frame member towards the second part to a position where a mating surface of each of the half-cores are in surface-to-surface alignment with each other. Second actuation means drives the aligned mating surfaces into intimate contact or moves the first frame member away from the second part.

Abstract: A make and break inductive connector for transferring electrical energy, e.g. under water, by transformer action comprising two separable body parts (11) having mateable end faces (13). Each part has a cavity (15) extending into it from its end face and a magnetic pot core half (17) housed in the cavity so that the end of the pot core half is flush with the body part end face. Within an annular cavity (23) of each core half there is housed a toroidal electrical winding (25) and potting compound occupies the otherwise free space of the body part cavity, including the cavity in the pot core half, so as to enclose the winding completely and preclude direct contact between the winding and the pot core half.

Abstract: In a similar-redundant signal system employing two or more channels, the signals in the different channels below a predetermined frequency are equalized, the equalization preferably being performed digitally. The equalization reduces the slight differences between signals in the different channels in the absence of channel failure, and thus enables the thresholds for channel failure detection by comparison of the signals in different channels to be reduced.

Abstract: A communication system enables a plurality of wide band signals to be carried over a common signal path. Each one of the information channels is used to amplitude modulate selected half-cycles of a common carrier signal. Because successive half-cycles of the carrier signal contain information relating to only one of the information channels any non-linearities in the transmission system do not introduce intermodulation distortions. Successive half-cycles of a carrier signal 5 are routed to separate amplifiers 15, 16, 17 and 18, and the gain of each amplifier is controlled by the signal amplitude of respective information channels 1, 2, 3 and 4. The various half-cycles are then combined at a combiner 21 to re-form the carrier signal which is transmitted over a signal path to a receiver. One of the channels is provided with an identity marker to enable the information channels to be correctly separated and identified at the receiver.

Abstract: An angular position sensor, suitably for use in a helmet sight system, comprising a link member (3) connected by first and second (5 and 49) coupling means respectively to first and second fixing means (7 and 57, 59, 63) whereby the sensor may be attached between two bodies (1 and 61) whose relative angular position is to be sensed. The first and second coupling means respectively define axes of permitted angular movement of the first and second fixing means with respect to the link member and are associated with angle sensing means (21, 23 and 51, 53) providing electrical outputs representative of the angular positions of the fixing means about these axes. The sensor further includes a third coupling means (29, 31, 33 or 57, 59) whereby the fixing means may be moved translationally with respect to one another without altering any of the outputs of the angle sensing means.

Abstract: An assembly comprising a board 1 and a mechanism 17 for clamping a marginal portion of the board adjacent an edge between two opposed substantially flat parallel walls 7a. The mechanism 17 is mounted on a major surface 19 of the board 1 and includes a spring strip 21 extending longitudinally along the mechanism, and having corrugations transverse to its length. An elongate cam 27 extends along the length of the strip 21, overlying the strip, and being supported for rotation about its longitudinal axis. Rotation of the cam 27 causes expansion of the mechanism 17 in a direction normal to the surface 19, limitation of the expansion by the walls 7a leading to compression of the corrugations in the strip 21.

Abstract: An optical device suitable for attachment to headgear (13) such as a pilot's helmet, for use as a night vision goggle (11) wherein an image intensifier (19a or 19b) whereby radiation in the visible and/or near infra-red portions of the spectrum received from the scene to be viewed is converted to visible light is arranged so that its input (33a or 33b) and output (21a or 21b) faces are directed respectively away from and towards the scene to be viewed, light from the output face being reflected to the user's eyes by a viewing eyepiece (23a or 23b) which intercepts the user's line of sight, and the received radiation being directed onto the input face by an objective and ray-folding means (27a or 27b; 29a or 29b; 31a or 31b). A design of goggle which is lighter and has a smaller forward projection can be achieved in goggles using such optical devices.

Abstract: A marine vehicle, which may comprise a sidewall gas-cushion vehicle, is provided with a pair of steering rudders, a sensor for detecting incipient undesirable motions of the vehicle, and an electrical, mechanical, and/or hydraulic system, or a hybrid thereof, for operating the rudders so as to apply restoring forces to the vehicle. The steering rudders are mounted beneath the vehicle and on opposite sides of the longitudinal axis thereof, being disposed in planes which are inclined to the vertical and which intersect above the rudders. The sensor for detecting incipient undesirable motions of the vehicle may comprise an angular rate and/or an accelerometer. The signal output of the sensor is applied to a band pass filter of pre-determined transfer function and the filtered sensing signal is applied to a summing point, to which is also applied a steering command signal.