Abstract: Radar display apparatus employs digital techniques to convert range/azimuth scan to T.V. scan. A digital store contains data defining the brightness of levels for the picture cells of a T.V. display. The store is continuously updated in accordance with received video from a digitiser. The correct cell in the store for updating is identified by converting polar coordinates to Cartesian coordinates in a Sin .theta., Cos .theta. generator and integrators. The contents of the store for the addressed picture cell is modified by a control unit in accordance with the digitised video return so as to represent the degree of positive correlation of returns in that cell on successive azimuth scans of the radar. Thus the brightness or color of the cell on the T.V. display represents this degree of correlation.

Abstract: A notch filter is provided with an ancillary circuit including a non-inverting amplifier and a coupling which enables the filter to form part of an oscillatory loop of which the frequency of oscillation corresponds to the frequency of maximum rejection by the notch filter. Measurement of that frequency facilitates the tuning of the notch filter, which includes capacitors constituted by varactor diodes. The gain of the ancillary circuit may be adjusted to change its mode of operation from oscillation to that of a tuned amplifier so that a sweep of the center frequency of the notch filter through a range of interest facilitates a search for an unknown interfering frequency and the simultaneous tuning of the notch filter to reject that interference.

Abstract: In a frequency modulated carrier wave radar the detection of the beat frequency that represents range is interrupted for short intervals that occur near maxima or minima of the modulating signal that controls the frequency of the transmitted carrier wave. During these intervals of interruption the carrier wave is modulated in amplitude so that it can convey information to the target that it illuminates. In a preferred embodiment, the amplitude modulation consists of a variable number of cycles of a voltage controlled oscillator of which the frequency is controlled by an integrated signal which represents the beat frequency. Timing for the short intervals of amplitude modulation and somewhat longer intervals that extend before and after each interval of amplitude modulation is derived from a square wave signal that is produced by an oscillator that governs the frequency of the carrier wave.

Abstract: An automatic tape winder in which a splicer includes a tape applicator which includes a holder which moves back and forth along a length of splicing tape, holding it by vacuum suction to draw it from a stock and passing it via a cutter to a punch which holds it by vacuum suction. Also described is an extractor which blows leader tape from a cassette to a clasp which draws the leader over a splicing block.

Abstract: A self-illuminating panel in which characters are unobtrusively illuminated by projection of light into a narrow face of a transparent flexible lamina marked with the characters. Each character, which may be a translucent printed figure, provides an optical discontinuity which disperses the light so that the diffusely illuminated character can be viewed in contrast against a dark background behind the lamina. Pressure applied on and through the flexible lamina enables operation of an array of switches disposed behind the lamina.

Abstract: An automatic tape winder in which a splicer includes a tape applicator which includes a holder which moves back and forth along a length of splicing tape, holding it by vacuum suction to draw it from a stock and passing it via a cutter to a punch which holds it by vacuum suction. Also described is an extractor which blows leader tape from a cassette to a clasp which draws the leader over a splicing block.

Abstract: A vibratile optical boresight which can be used for conical or nutating scanning of a target by a beam of light. A lens is mounted for vibration, in at least one direction in a plane normal to the axis of the lens, between the free ends of piezo-electric cantilevered plates which are trihedral, tapering towards the free ends. The lens is carried in a canister which has arms extending to the cantilevers. The arms and the cantilevered plates can flex in a common plane to which the axis is normal.

Abstract: An optical detector of remote vibration, comprising a system for obtaining a Doppler signal by mixing reference light with laser light reflected from a vibrating object. The Doppler signal is rectified and the successively highest value of it are stored. The laser light is scanned over the object and the values of scanning waveforms at the time of storage of a maximum return signal are stored, the stored values being read out to control the direction of the laser light so as to locate the region giving maximum return.

Abstract: A detector of remote movement in which light from a laser is directed at a target and, on reflection from the target, is mixed with reference light from the laser to produce a Doppler signal denoting the movement of the target. The beam of light from the laser is directed through an optical system which brings the light to a focus and thereafter projects the light from the focus at the target. The optical system includes a lens which is mounted in a ferromagnetic carrier which can be vibrated in two orthogonal directions each normal to the axis of the light beam and the axis of the lens. Coils disposed to produce these orthogonal movements are energized in quadrature so as to produce conical scanning of the beam of light on the target.

Abstract: An optical path-length modulator which comprises a tube having at one open end a lens of which the focal length is equal to the distance between this lens and the surface of a concave mirror which is disposed at the closed end of the tube and which has a radius of curvature equal to the focal length of the lens. The tube is carried between and mounted on two spaced apart diaphragms which can flex in order that the tube may move axially. The tube constitutes an armature for an electromagnetic vibrator which includes also pole pieces surrounding the tube and a driving coil on one of the pole pieces. Energization of the driving coil causes to and fro axial movement of the tube. Collimated light entering the tube via the lens is brought to a focus at the surface of the mirror and is rereflected the way it entered.

Abstract: Pulse radar apparatus particularly for marine use has a dispersive antenna so that transmitted pulses sequentially of two or more different frequencies are radiated in different azimuthal directions. The antenna is continuously rotated and the receiver has separate channels for the different frequencies and display means correlating information received on different frequencies from the same azimuth thereby to reduce sea-clutter on the display.

Abstract: A clamping circuit in which a signal such as a line sequential color television signal is clamped to a reference, such as a black level by means of a corrective signal which is the integrated output of a current multiplier. The gain of the multiplier, which is fed with a signal corresponding to the difference between the signal that is to be clamped and the reference, varies from a maximum to a minimum during a period of clamping. Large initial error in the signal can be rapidly corrected and the final corrective signal corresponds to the average error during the period of clamping.

Abstract: A loudspeaker system in which two loudspeakers that cover different but overlapping frequency ranges, for example a treble range and a bass range, are mounted to radiate from co-planar mouths. Phase delay which is introduced by the radiator for the lower range is compensated by an acoustic delay which is disposed between the radiator of higher optimal frequency range and its mouth. This acoustic delay preferably takes the form of an exponential horn which introduces a delay corresponding to the displacement, from the common plane of the mouths, of the effective source of signals radiated by the lower frequency radiator at the crossover frequency in the overlapping region.

Abstract: Apparatus for forming a uniform film on a planar surface of a planar support, particularly for forming thermoplastic films on conductive support members, comprises a drivable turntable having means for removably locating the planar support and having a distributor, mounted for rotation with it, a housing enclosing the turntable and the support, and a dispenser, located in the housing for delivering a charge of fluent material to the distributor. The distributor is arranged to distribute fluent material radially outwardly onto the planar surface of the planar support, and has at least one portion extending axially from the turntable. The dispensing means is located with its outlet over the distributor.

Abstract: A projector for projecting a movable spot of light onto a screen includes a pair of plates mounted adjacent and parallel to each other, each plate being opaque, apart from a straight slot. The slots cross one another at a crossing point defining an aperture which is transparent to light from a light source. The plates are mounted to be independently movable in such a way that the aperture is selectively displaceable thereby to allow controlled movement of the spot on the screen.

Abstract: A line-sequential color television system in which each line of a transmitted signal is compared in a decoder with an earlier line of corresponding chrominance and each line is averaged to form a luminance signal. The signals thereby derived are used to reconstitute the luminance component of the transmitted signal to preserve vertical detail therein notwithstanding any averaging of the transmitted signal for the extraction of chrominance components.

Abstract: Apparatus for retaining the data held in a directional counter in the event of the voltage level supplied to the counter falling below a predetermined level comprises a directional counter means for comparing the level of voltage supplied to the directional counter with a predetermined voltage level, data storing means responsive to the comparator means for storing the output signal of the directional counter when the voltage falls below the predetermined voltage and for loading the stored output signal into the directional counter when the voltage level subsequently rises above the predetermined level.

Abstract: This invention concerns a method of recording wide-band signals on a thermoplastic film. The signal to be recorded is converted to an intensity modulation of a beam of electrons which is directed at the surface of a thin thermoplastic film carried on a conductive substrate. The film is rotated in its own plane and simultaneously translated so that the beam scans the film in a track which follows a spiral path. The deposition of charge produces after heating of the film a spatial modulation of the film. The intensity of the beam and the beam's impingement on the film is controlled in order that the charge pattern is appropriate for the formation of a spiral groove which is substantially invariant in cross-section but varies in depth along its direction of progression in accordance with the signal that modulates the intensity of the beam of electrons. The recording thus made can be used for the production of video discs capable of mechanical playback.

Abstract: A transmission system receiver compares the received signal power in a relatively narrow frequency band with the received signal power in a relatively wide frequency band, which embraces the narrow frequency band, to obtain an indication of the "SINAD ratio" which refers to the signal plus noise plus distortion to noise plus distortion ratio. The receiver also includes an automatic control system for comparing the indication with a reference and for adjusting an attenuator in response to disparity between the indication and the reference in a sense to increase the SINAD ratio above a predetermined level, or to adjust the SINAD ratio to an optimum value.

Abstract: A method of making disc records, particularly video discs from thermoplastic sheet material. In a press a thin flexible matrix is disposed between the sheet, which is backed by a resilient cushion, and a flexible diaphragm which constitutes a wall of a hydraulic pressure chamber.