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 method of making a humidity sensor comprises providing a host device constituted by a semi-conductor substrate (10) and a gate insulator (13) of an insulated gate field effect transistor, forming a layer (14) of poly (vinyl) alcohol (PVA) on the exposed surface of the insulator, heat treating the layer to crystallize and stabilize the PVA, and forming a gate electrode (15) on the PVA layer, so that the gate electrode is porous allowing ambient water vapor to be absorbed by the PVA which, in response, undergoes a change of bulk dielectric constant, thereby causing a change in gate capacitance of the transistor resulting in a detectable change of electrical conductivity in the drain source channel.

Abstract: A circuit (FIG. 1) for generating a current impulse comprises an avalanche transistor 2 which responds to a stimulus to apply an electrical impulse to the bases of a plurality of further avalanche transistors 3, 6. The further transistors respond to the impulse to discharge respective equal capacitors 9-12 through a laser diode 7. Further equal capacitors 22-25 connect the emitters of the transistors to the common junction of the transistor 2 and an impedance 21 to generate the electrical impulse when the transistor 2 responds to the stimulus. The arrangement of the further capacitors ensures that once one further transistor begins to conduct, the electrical stress on the others is increased, thus ensuring the further transistors simultaneously avalanche.

Abstract: A signal generator produces a spread-spectrum bandwidth signal in the frequency range 40 to 90 KHz for use in a domestic mains signalling system. In the generator, sixteen individual frequencies, equi-spaced in that range, pass to samplers operating at a clock frequency of 204.8 KHz and then to quantisers before storage. The resulting signals are then assembled in appropriate manner by selector switch before being filtered when (temporarily) in the frequency domain.The resultant signals duly reach catalogue store, whose output can be used for programming an EPROM in a mains signalling interface unit.

Abstract: A communication system utilizing the electrical-supply wiring of mains circuit has an interface unit for an intruder-sensor. Unit has a transmitter for sending FSK-modulated messages and a capacitor to store adequate energy to power transmitter only for the time-duration of a message. The system also has a interface unit for a temperature sensor.

Abstract: The signalling network has a main control unit which can communicate with any of a number of home units each associated with a separate household. Some home units have signal-repeater facilities. Each of the control units and the home units has an address identity unique in the network.When a signal is sent out targeted at a specific home unit, the main control unit monitors for acknowledgement of reaching its destination. If no such acknowledgement is received, the main control unit sends out the signal again, but re-routed via an intermediate home unit with a repeater facility.

Abstract: A signal generator produces a spread-spectrum bandwidth signal in the frequency range 40 to 90 KHz for use in a domestic mains signalling system. In the generator, sixteen individual frequencies, equi-spaced in that range, pass to samplers operating at a clock frequency of 204.8 KHz and then to quantizers before storage. The resultant signals are then assembled in appropriate manner by selector switch before being filtered when (temporarily) in the frequency domain.The resultant signals duly reach catalogue store, whose output can be used for programming an EPROM in a mains signalling interface unit.

Abstract: The IFF system uses basic identification codes which are transmitted between an interrogator and a responder. The basic codes are chosen in dependence upon the time and position of the interrogator or responder at the time of choice. In one version of the system, the lifetime of a code is less than or equal to the propagation time of a radio signal for a given maximum range between the interrogator or responder. Interactive interrogation may also take place using codes chosen in the same way as the basic codes. Local information may also be transmitted between the interrogator and transponder. An example of apparatus for performing these operations transmits basic or other codes together with a time code defining the time of production of the basic or other codes. It is not essential to transmit a time code in some circumstances. Position and time information may be gained from an external communications system.

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: In a computer-assisted tomography (CAT) apparatus, in which a fan-shaped X-ray distribution is rotated about the patients body, it is possible to use a ring of stationary detectors disposed to receive the radiation after passage through the body. In this arrangement the ring of detectors is of smaller radius than the locus of motion of the radiation source. It would appear that this would cause the detectors to obscure the body from the radiation. An arrangement disclosed moves out of the radiation beam those detectors which would present an obstruction so that only those required to collect radiation lie in the beam.