Abstract: A bandwidth reduction system for television signals employs three spatial filter circuits capable of imposing respective resolution characteristics on the signals. The filters are selectively switched into the path of the signals in dependence upon the degrees motion occurring in respective spatial portions of the television picture. A relatively high resolution is allowed where virtually no movement is taking place and a relatively low resolution where rapid movement is taking place. Intermediate resolution is imposed where the degree of motion in a given spatial portion of the television picture is finite but less than said rapid movement.

Abstract: Arc discharge lamps driven at frequencies in excess of 20 kHz may exhibit the phenomenon of `acoustic resonance` in which longitudinal and lateral acoustic waves are supported in the arc tube. This is a problem because the acoustic wave may give rise to an instability in the discharge arc, causing it to stretch or gyrate and invariably to extinguish. In some cases damage may be caused to the arc tube. A power supply suitable for an arc discharge lamp comprises a drive circuit arranged to supply voltage to the lamp and control means for causing a characteristic of the voltage to vary, with time, in accordance with a pseudo random sequence in order to reduce, or eliminate, acoustic resonance in the lamp.

Abstract: A fluorescent lamp discharge tube has an electrostatically coated envelope. The coating comprises a mixture of 100 parts by weight of phosphor, 0.01 to 3 parts by weight of a fatty acid having a melting point greater than 40.degree. C. or the ammonium, aluminum alkaline earth salts thereof, and 0.05 to 5 parts by weight of finely divided aluminum oxide having a grain size smaller than 0.1 micron. The phosphor is applied to the tube by a venturi effect and results in a more uniformly applied coating than is provided using a suspension coating. Uniformity of the coating is measured by the disclosed optical densitometry test.

Abstract: A ceramic metal halide high pressure discharge lamp has an arc gap separating the discharge electrodes which is not more than 10 mm and a wall loading which is at least 50 W cm.sup.-2. The relatively small arc gap enables a relatively low operating voltage (in the range from 80V to 130V, say) to be used.

Abstract: A liquid crystal display has a matrix of pixels each with a continuously clocked counter used both as the data store and as the mechanism of grey scale generation. The grey level of each pixel is stored as the phase of the counter with respect to a reference count.The data bus, load clock, counter clock and master phase reference are all lines which transport signals common to a large number of pixels.The shift data line is used to propagate a bit which enables the counter load input. Each pixel circuit instructs the adjacent circuit that it is next to be loaded, by use of a clock delay. Thus pixels are loaded in sequence from data on the load bus, that data being between load clock pulses. The bistable circuit element, set from the master timing and reset from the counter, has an output which directly drives a bistable liquid crystal display device.

Abstract: An antenna has a resonant cavity defined by electrically conducting plates and a sidewall, and has sixteen helical antenna elements each with five turns in the helical section and a probe at the opposite end, the stem of probe passing through an aperture in upper plate so that its end is within the resonant cavity common to all elements in that module.The cavity has a cross-section parallel to the plates essentially square in shape except for the presence of four inwardly-protruding buttresses, one situated mid-way along each side of the cavity to promote the formation of standing waves of different mode, and thereby enhance the frequency range of the array.

Abstract: A temperature sensor is incorporated within a housing having a silicon window through which infra-red radiation can enter. Mounted on a support structure is a semiconductor fabrication consisting of a reference junction and a sensing junction, covered with a black absorber. The reference junction is responsive to the temperature of the housing, whereas the sensing junction is responsive to the temperature of the housing and also the temperature of a remote zone from which infra-red radiation can enter the housing via the window. A Peltier heater/cooler controls the temperature of the housing, which temperature is monitored by a sensor to provide a measure of that of the remote zone.

Abstract: An ionically conductive accelerometer comprises a body of an ionically conductive material provided with at least three electrodes which are so arranged as to define a respective ionically conductive path extending between one of the electrodes and each of the other electrodes. The accelerometer is responsive to an acceleration or a component of acceleration acting along each path.

Abstract: A device for measuring fluid density, the device comprising a silicon substrate having a micro-engineered cantilevered beam fabricated on it for use as a density sensor. The beam is at the end of a tube and has a contact manufactured on its end and a contact manufactured on the substrate below the contact. Means for causing said structure to vibrate and for detecting a characteristic of the vibration are provided, the characteristic being dependent on the density of the fluid to be measured.

Abstract: An ionic conductivity accelerometer comprises a layer of an ionically conductive material such as rubidium silver iodide (RbAg.sub.4 I.sub.5) deposited on an electrically insulative substrate with spaced electrodes in contact with the layer. The ionically conductive material may be mixed with an electrically insulative, chemically inert material such as quartz wool in order to alleviate susceptibility to cracking.

Abstract: A spotlight comprises a light source (14) mounted within an enclosure (11) fitted with a light-transmissive cover (28) which is formed with a central opening (29) above the light source. A clearance space between the light source and the cover allows light from light source (14) to spill over into the enclosure and thereby illuminate the cover from behind. Another enclosure (12) containing control gear (17) for the light source is thermally insulated from enclosure (11) by an air gap (21).

Abstract: Equipment for labelling audio signals with identification information has an encoder which inserts the binary information into two very narrow notches of center frequencies 2883 and 3417 Hz, between semi-tones in the tonic scale to minimize music breakthrough into the decoding circuits, and to ensure that no fundamental frequencies in the tonic scale will be excluded in the reproduction. The notches are derived from a 3-stage biquad filter, and are approximately 50 dB deep and 150 Hz wide at the top. The encoder includes a wide bandpass circuit consisting of a 1 KHz highpass filter and a 6 KHz lowpass filter introduced to ensure that the code insertion level is not determined by frequencies, either high or low, which do not adequately mask the code frequencies. The code amplitude is kept a fixed level below the programme, initially adjustable by a suitable control.

Abstract: A sensor arrangement is described in which a semi-conductor component, such as an ion-selective field-effect transistor (ISFET) is secured to a ducting component containing ducts to carry fluid towards and away from a sensitive region of the ISFET. The two components are secured together by means of a gasket formed of porous material and apertured where adhesion of the components to one another is not required. The gasket is inserted between the components and adhesive applied to an exposed portion, such as a tab, of the gasket. The adhesive is distributed by capillary action to all parts of the gasket and secures the components together without affecting those areas of the components juxtaposed with the apertured region or regions of the gasket.

Abstract: The liquid crystal display unit 1, has a video signal receiver 2 and a store 3. Time-modulation grey-scale addressing of the ferroelectric liquid crystal pixels in a display panel 4 is provided to a store 10 which records the number of changes of state for each pixel during one picture-signal. Once the most-significant bit has been processed and is being displayed on the panel 4, the change-of-state store 10 has the net number of changes which the pixel has undergone in that picture. Controller 11 causes store 10 to output the value appropriate to that pixel and pass it to driver unit 9 to produce a compensating pulse (whether positive, negative or zero) necessary to ensure that there is no net electrical potential over the entire picture interval. The display produced by the compensating pulse is cleared immediately the first data of the next picture is input to the pixel.

Abstract: A heating element comprises an electrically resistive track intended to be formed on an electrically insulative substrate. A heating unit comprises a heating element and a temperature sensor on a substrate, the sensor comprising an electrically resistive track. The track consists of a thick film having in the temperature range of from 0.degree. C. to 550.degree. C. a temperature coefficient of resistance in excess of 0.006 per degree C. The thick film includes a metal and a glass in such proportions as to provide a suitable resistivity and a thermal expansion coefficient to match that of an electrically insulative substrate to which the track is to be applied and to permit adhesion of the track to the substrate.The considerable variation of the resistance of the track with temperature provides advantages in both of the aforementioned applications.

Abstract: A system suitable for determining the concentration of an enzyme's substrate in a solution 21 containing a buffer comprises two ion-sensitive devices 22, 23, such as ISFETS, in contact with the solution, one of the devices 23, e.g. an ENFET, having a layer 24 containing an enzyme, the enzyme producing ions from its substrate, and the system comparing the responses of the two devices and providing a control signal to consume ions as they are generated at the ENFET, or to produce an equal concentration of ions at the other device, such that the concentrations sensed by each are equal. The signal gives an indication of the concentration of the substrate. Other ion-sensitive devices may be used. The concentration of other substances can be determined, for example a device with an enzyme's substrate can be used for detecting the concentration of an enzyme.

Abstract: A signal receiver for use in a system for communication and telecontrol over the electricity mains network has a correlation stage in which values of correlation coefficients for a received signal are predicted in a processor taking due account of known distortions of the network. Then these coefficients are multiplied, shifted and averaged with recent results to minimise the effects of noise, the consequent values being multiplied by the actual correlation values of the received signal in the bins for comparison.

Abstract: A spotlight comprises a light source (14) mounted within a enclosure (11) fitted with a light-transmissive cover (28) which is formed with a central opening (29) above the light source. A clearance space between the light source and the cover allows light from light source (14) to spill over into the enclosure and thereby illuminate the cover from behind. Another enclosure (12) containing control gear (17) for the light source is thermally insulated from enclosure (11) by an air gap (21).

Abstract: A hydrogen getter for use within the arc tube assembly of a gas discharge lamp e.g. a high pressure sodium discharge lamp, comprises a layer (11) of a getter material (eg Ti) sandwiched by diffusion bonding between layers (12, 13) of a hydrogen permeable material (eg Nb) there being an exposed region of getter material. Hydrogen getters in the form of disc-like washers are formed from the sandwiched layers by a stamping process.