Abstract: In a computerized tomographic apparatus in which the requisite absorption data are derived by rotating a source of fanned radiation around a body to be examined and detecting radiation emergent from a cross-sectional slice of the body at many times during the rotation the data, when assembled into sets relating to parallel beam paths through the slice, tends to relate to beam paths which are non-uniformly spaced across the slice. Some techniques for processing such data to produce a representation of the variation of absorption of said radiation over the slice should preferably have said data presented thereto in the form of sets relating to substantially uniformly spaced, parallel beam paths. The application of this invention provides considerably more data then is actually required for the processing so that data relating to beam paths of the required numbers and dispositions can be derived therefrom.

Abstract: A submunition has a metallic body 1 a sensor 4 for sensing the presence of metal and an extendable probe (e.g. a spring 3) separating the sensor 4 and body 1 to avoid interference with the sensor. A circuit including the metal sensor and an impact sensor detonates the submunition if impact with a metal body is detected; if impact only is detected the submunition adopts the role of a mine.

Abstract: A focussing system in which a detection and processing device (2) scans the image plane, in raster fashion, to generate a video signal representing the intensity of radiation prevailing at successively scanned locations. A selection circuit (6) contains a programmable memory which generates addresses suitable for selecting discrete sets (S) of neighbouring locations and a circuit (7) is responsive to the addresses to access to a processing circuit (8) only those portions of the video signal which correspond to the sets (S) of locations. The processing circuit (8) generates difference signals representing differences of intensity between neighbouring locations and evaluates the number (P.sub.tm) of difference signals exceeding each of a number of preset threshold values (t.sub.m) to generate a histogram. The numbers constituting the histogram are then weighted and scanned to generate a control signal (F) representing the focus.

Abstract: A process for producing an inorganic foam includes mixing a metallic compound, such as aluminum and/or magnesium nitrate, into a slurry with an acid or acidic solution, such as acid phosphate solution, and then heating the slurry to a predetermined temperature for a sufficient length of time to decompose the metallic compound to the metallic oxide. After the decomposition, reaction can occur between the metallic oxide and the acid or acidic solution to produce a strong binding medium for the foam. As formation, and consequently hardening, of the binding medium cannot commence until after the heating stage, hardening of the binding medium can be controlled to prevent premature hardening before the binding medium is applied to its working environment.

Abstract: A receiver for the demodulation of FSK signal for passage to ancillary equipment has an error-corrector prior to demodulator. In preparing received signals for error-correction, they are passed to a counter which notes the number of cycles within each symbol of the signal. Thereafter, this count is used by a calculator and a classifier to derive a confidence level indicating the degree of certainty of the symbol having the carrier frequency. This confidence level is used in the error-correcting and/or demodulation operations.

Abstract: In a receiving circuit a control circuit and a direction finding circuit generate a digitally encoded "descriptor" which characterizes pulses of r.f. radiation received in a particular azimuthal direction and having a particular carrier frequency. The "descriptor" may be compared with data stored in a processing circuit representing r.f. pulses emitted by sources which have already been detected or which are known to exist. To reduce the workload on processing circuit a number of emulator circuits generate pulse patterns which simulate pulses produced by known sources of little inherent interest. If the received pulses match the simulated pulses a gate inhibits control circuit.

Abstract: A circuit for generating an output signal L indicative of the mean clutter level at a selected location in the field of view of a radar apparatus, particularly the sea surface which exhibits a swell pattern. The circuit includes processing circuits which generate weighting coefficients (a.sub.1, a.sub.2, . . . a.sub.N) used to weight the amplitudes of returns derived respectively from a group of N discrete locations which precede in range and or succeed in range the selected location. The circuit generates the elements r(n) of a matrix [r] which represents the auto correlation function of the amplitude of returns derived from w discrete locations encompassing the group of N locations. Circuit then uses the matrix [r] to compute the weighting coefficients (a.sub.1, a.sub.2. . . a.sub.N) which are stored at 13 applied to respective multiplying circuits to weight corresponding amplitudes accessed to respective locations of a shift register.

Abstract: In a radiographic apparatus, a source of radiation is arranged to scan a planar spread of radiation in a plane about the body of a patient being examined. A plurality of detector devices is arranged to provide data representing the absorption of the radiation along a plurality of paths within the spread, for different orientations in the plane, for processing to determine a distribution of absorption coefficients for a planar slice of the body. The arrangement is such that a predetermined number of the detector devices are irradiated by the spread of radiation at any time and the actual devices irradiated change progressively as the scan progresses.

Abstract: A set of stores contains reference information representing a reference pattern. A scene is scanned and information derived from each of a succession of portions of the scene is fed to the stores which produce correlation signals if the scene information of that portion correlates with the reference information.The position of the portion of the scene which is fed to the stores is tracked, and the position associated with the highest correlation score is used as a representation of the position in the scene of the reference pattern.

Abstract: An echo cancelling system incorporated in a conventional echo canceller with additional circuitry to provide tracking and compensation for drifting of any D.C. offset generated.Upon initial energization of the system (i.e. before data signals are processed thereby) an output signal e.sub.1k from an error signal input device represents a D.C. offset value generated by the components of the system.This value is stored in a D.C. offset register, the loading of which is controlled by a load/inhibit signal. Refining of the stored value during data processing is achieved using predetermined increments .DELTA..sub.1 for half-duplex mode and .DELTA..sub.2 (of smaller size) for full-duplex mode.

Abstract: Transverse bowing of a plastics web coated with a magnetic thin metal film is substantially eliminated by laterally stretching the coated web such that the lateral stress applied to the metal film exceeds the tensile strength of the film and the lateral stress applied to the plastics web lies within the yield point of the plastics material. The coated web is stretched by passage over a curved roll adjusted to provide a lateral strain of at least 1% and typically 1.8% in the web, and such stretching may cause a pattern of interlaced micro-cracks to occur in the metal film. Recording tapes slit from such stretched webs exhibit negligible cupping, and the pressure of micro-cracks has no adverse effect on recording performance or wear.

Abstract: A Local Area Network consists of a number of stations connected together by a transmission line, each station having a transmitter and a receiver. A transmitter generates a sequence of information signals having individual message portions separated from one another by flag signals, each message portion having a predetermined number of symbols. A receiver processes a message portion by analyzing the content of each section formed by dividing the message portion into the predetermined number of equal parts. The receiver includes stores and, a detector, a signal-divider and a unit which determines a representative value.

Abstract: A process for producing an inorganic foam includes mixing a metallic compound, such as aluminum and/or magnesium nitrate, into a slurry with an acid or acidic solution, such as acid phosphate solution, and then heating the slurry to a predetermined temperature for a sufficient length of time to decompose the metallic compound to the metallic oxide. After the decomposition, reaction can occur between the metallic oxide and the acid or acidic solution to produce a strong binding medium for the foam. As formation, and consequently hardening, of the binding medium cannot commence until after the heating stage, hardening of the binding medium can be controlled to prevent premature hardening before the binding medium is applied to its working environment.

Abstract: A method and apparatus for imaging a target, such as a ship, exhibiting rotational movement about respective, mutually orthogonal axes. The method involves identifying a scattering center at the target exhibiting rotational movement about one axis only (the yaw axis, say, in the case of a ship) and then correlating an electrical signal related to the Doppler frequency of a return derived from that scattering center, and indicative of the angular velocity of the target about the one axis, with other electrical signals related to the Doppler frequencies of returns derived from other scattering centers. Correlation signals generated in this way provide an indication of the relative positions of the other scattering centers in relation to the one axis.

Abstract: A compliant coupling mechaism has a first part (10) connectable to a robot arm (A) and a second part (20) connectable to a robot gripper (G). The mechanism is arranged to allow displacement of the second part relative to first part along a ZZ axis direction, and to allow further relative displacement along and/or about (XX) and (YY) axis directions. A locking device (40) prevents such further relative displacement unless a displacement along the (ZZ) axis direction exceeds a preset amount.

Abstract: High-definition video signal are produced using processing equipment incorporating a unit with two vertical-aperture circuits and and an interpolator, the former taking the signals A and C, passing them through a summation amplifier and a divide-by-two invertor. After combining this signal with B at the summation amplifier, the output signal .DELTA.B (which represents the vertical detail signal of B as compared to the signals A and C) is passed through a noise-coring circuit and any resulting output output added to B at the summation amplifier to produce a signal B* with enhanced vertical detail. Then signals B* and C* are averaged and alternately connected to the output of the unit, thereby to produce a high-definition video signal.

Abstract: In a control system for a robotic gripper a processing circuit (10) controls movement of the gripper (20) on a prearranged path. An article (A) held by gripper (20) comes into contact with the probe member (32) of a "known-down" sensor (30). A support assembly (33), on which the probe member (32) is mounted, is displaced with respect to a base member (31) allowing a continuous, uninhibited movement of the gripper along the path, even after contact has been established. In an alternative arrangement the sensor is mounted on the gripper and establishes contact with an article located at a fixed work station.

Abstract: A digital buffer store 25 (FIG. 2) stores digitized samples of a video signal. A circuit 206 determines the mean grey level (f(b)) of the stored signals and a circuit 28 forms a histogram indicating the number of pixels having various ones of 8 possible grey leves. A circuit 29 determines the dispersion of the histogram about the mean grey level. In principle, circuit 29 could determine from the means level and the histogram the statistical distribution of pixels amongst the grey levels and from that determine the standard deviation as a measure of dispersion. In practice, the circuit 29 determines an emirical approximation to the dispersion, ##EQU1## where n=number of binary bits=3N.sub.i =number of pixels having a grey level iA=f(b)=mean grey levelN.sub.A =number of pixels having the means grey level.This equation is advantageous as it operates on powers of 2.The circuit of FIG. 2 compares the determined values of f(a) and f(b) with empirically derived desired values and servoes the gain and D.C.

Abstract: An antenna is formed of four arrays each having sixteen helical antenna elements with probes located within a common resonant cavity. Thus cavity is used to combine all the outputs of elements.The elements of array are arranged over the surface of box such that the probes are located at the voltage antinodes of the resonance field patterns in order to maximize the coupling efficiency. Likewise the output probe for each cavity 6 is also located at a voltage antinode; output probe enables the signal combined in cavity to pass into a waveguide, also connected to other arrays and, for passage to the television receiver.

Abstract: An ammonia gas sensor comprises a dual gate field effect transistor (FET) in which the two gate electrodes are of platinum deposited respectively by sputtering and evaporation. The gate regions of the two FETs are connected together differentially and the net drain source voltage represents the concentration of ammonia gas to which the sensor is exposed.