Abstract: An electric amplifying arrangement for supplying current to an inductive load in response to an input signal of saw-tooth waveform, e.g. a deflection amplifier for a cathode ray tube, wherein during the ramp portion of the input voltage a linear relation is maintained between variation in the load current and the input signal (i.e. Class A operation occurs) and, during flyback, energy recovery is provided, thereby providing higher efficiency than is obtained with known Class A saw-tooth amplifiers.

Abstract: Apparatus for supporting a first structure on a second structure so that relative movement between the two structures is permitted in three mutually perpendicular directions only comprises three flexible shafts connected between the first structure and the second structure and mutually inclined so that their axes of torsional restraint intersect at a position at or relatively close to the center of mass of the first structure and a load carried by the first structure. The apparatus may include damping means connected between the first and second structures to provide a vibration and shock isolating arrangement and lying in a common plane which includes the center of mass of the first structure and a load carried by the first structure.

Abstract: A display unit for a vehicle head up display system in which the optical data to be displayed is obtained from a projector having a generally rectangular output aperture and the projected optical data is reflected to an observer by partially light reflective, partially light transmissive films embedded in a body of light transmissive, refractive material through which the observer views the distant real world scene, each film providing the observer with a different field of view of the projected data.

Abstract: An audio frequency muting arrangement includes one circuit for detecting intelligence signals in a received audio frequency signal, and a further circuit for detecting noise signals, so as to compare the levels of the noise and intelligence signals and to control a muting switch in dependence thereon. The invention is applicable to noisy environments, e.g. aircraft, in which a threshold circuit is used to track the ambient noise level. Particular signal detection circuits are described.

Abstract: An aircraft instrument comprising equipment for providing a first signal which is a function of airspeed and suitable for use in controlling an aircraft by variation of the airspeed to a predetermined value, an apparatus for providing a second signal which is a function of lift and suitable for use in controlling the aircraft by variation of the airspeed to adjust the lift to a predetermined value, and a selecting apparatus arranged to apply the second signal to a signal utilization mechanism for controlling the aircraft in accordance with said second signal except when said second signal falls below a predetermined datum level, which represents a safe margin above stall, whereupon the first signal is applied to the signal utilization mechanism, the selecting apparatus being arranged to provide a transition between control by the first signal and control by the second signal which is shorter than a transition between control by the second signal and control by the first signal.

Abstract: An angular position sensor having a housing with an aperture in the form of two mutually inclined slits. Behind the aperture is a linear array of light sensitive elements which intercepts laminar light beams developed by the slits from light from a small light source. The positions of interception of the light on the array constitute a measure of the angular position of the light source in elevation and azimuth.

Abstract: Electric signals in two narrow frequency bands arising from ground or airborne vibrations incident on one or more geophones at the perimeter of an area to be protected are monitored and an alarm given if signal components that are indicative of human footsteps near the geophones occur in both frequency bands two or more times within a predetermined period. These signal components comprise bursts of oscillations having steep leading edges and durations of some thirty to one hundred milliseconds, and there are provided means to rectify these bursts and to detect resulting pulse waveforms.

Abstract: Headgear incorporating an optical display system comprising, an optical data source mounted within the headgear above the level of the wearer's eyes, an image combiner having a spherical reflecting surface directed inwardly of the helmet and intercepting the wearer's forward line-of-sight, and a prism positioned and dimensioned so that a collimated, aberration free virtual image of the data source is presented to the wearer as a result of reflection of rays transmitted from the data source by way of the prism to the spherical reflector. Such aberration as is introduced by the prism compensates for aberration introduced by the spherical reflector.

Abstract: This invention relates to a head-up display unit having at least a part so disposed, when in use in a vehicle, as to intercept the line of sight of an observer using the unit to view a scene lying ahead of him. The display unit employs a light deflecting arrangement to enable the observer to see the part of the scene obscured by the unit and includes optical means for projecting light rays from a luminous signal source into the light deflecting arrangement thence to the observer, who sees the luminous signals superimposed on his view of the scene ahead.

Abstract: Test apparatus for a cathode ray tube has optical elements disposed along two optical paths from the screen of a cathode ray tube to two photosensors. One optical path passes through a graticule which has a pattern of light transmissive and non-transmissive areas. The real image of a luminous spot on the screen is accurately positioned on a boundary between two of the areas of the graticule by deriving a control signal from a comparison of the photosensor outputs.

Abstract: A double tripod arrangement in which the legs of a first tripod extend to a fixed angle and the feet of a second tripod are adjustably mounted on the legs of the first tripod. The first tripod forms a secure base on which the second tripod can be adjusted for height and for levelling.

Abstract: A vehicle head-up display system wherein symbols representing information required by an observer in the vehicle can be displayed in combination with a representation of the vehicle environment. First and second raster scan output signals of the same format respectively representing the desired symbols and the vehicle environment are produced by respective read-out arrangements from respective storage devices which respectively store representations of the desired symbols and the vehicle environment in response to input signals of different formats, the two raster scan output signals being combined for application to the display unit of the system.

Abstract: A television camera arrangement includes a read only memory for storing character or symbol information in a form which can readily be combined with normal video picture information to produce a composite display. For example a symbol indicating the identity of a camera can be included in its video output.

Abstract: A partially rotated arrangement fastens parts together in nearly perfect alignment. The fasteners utilize semicircular rings which are rotated about the circular axis until each ring lies partly in each of two adjacent parts. The parts so joined together may contain one or more fluid passages or form electric conductors, and more particularly, wave guides.

Abstract: A topographical map display device for a vehicle, such as an aircraft, wherein a map in miniaturized form is carried on a carriage coupled to a frame by way of a mechanism which permits translational planar movement only of the carriage with respect to the frame and an image of an area of the map is projected onto a display surface on which a fixed datum represents the vehicle position, the carriage being moved with respect to the frame by actuator means in dependence on the range and bearing of the vehicle with respect to a ground-fix position so that the image of the map projected onto the display device changes progressively with vehicle movement whilst maintaining a fixed orientation.

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 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 partially rotated arrangement fastens parts together in nearly perfect alignment. The fasteners utilize semicircular rings which are rotated about the circular axis until each ring lies partly in each of two adjacent parts. The parts so joined together may contain one or more fluid passages or form electric conductors, and more particularly, wave guides.

Abstract: A vehicle (e.g. aircraft) head-up display system having the capability of displaying, superimposed on an observer's view of the scene outside the vehicle, symbols representing information required by an observer in the vehicle, together with a pictorial representation of the vehicle environment produced by a signal source incorporating an imaging sensor. The signal source produces an output signal of raster scan format (e.g. a television type line-by-line scan format) and output signals of the same format representing the required symbols are developed by a storage/read out arrangement which stores the symbols in response to stroke writing mode signals and reads out the stored symbols in the same raster scan format as is employed by the signal source, the raster scan outputs of the storage/read out arrangement and the signal source being combined for application to the display unit of the system.