Abstract: A substrate for supporting electrical components, such as thick film resistive heating elements, comprises a plate member, such as a metallic plate member, coated on one or both of its flat surfaces with a glass ceramic material.It has been found that the problems of (a) electrical breakdown between the metallic plate member and the thick film resistive heating element and (b) lack of adhesion between the thick film and the glass ceramic material can be substantially reduced or eliminated by reducing the porosity of the glass ceramic material. Methods of producing a glass ceramic layer having a low porosity, involving a two-stage heating process, are described.

Abstract: A system for the remote reading of a gas meter includes an interface unit within a domestic residence but situated such that an input/output terminal for the interface unit is accessable from the exterior of the residence, and a hand-held meter reading unit for connection to the terminal in order to read and record the value of the gas consumption indicated by the meter. The meter reading unit has two LED sources, whose outputs are combined a Y-coupler, for passage into the interface unit when an optical fibre is connected thereto. At a multiplexer, the combined beam is dispersed according to wavelength and separately passes along a fibre array to respective roller digits of the tumbler for reflection or not according to the displayed reading. Reflected light passes back through the system, is divided at a Y-coupler and passes to a de-multiplexer such that the light returning in respect of the roller digits can be measured and displayed at a light detector and liquid crystal display.

Abstract: A helically scanned optical tape recording and replay system has a rotating drum with a galvanometer mirror for controlling the tracking of a number of write and read light beams during recording and replay. Dynamic focussing of the beams on the recording medium is controlled by means of a voice-coil actuator operating on a lens situated outside the drum. An optical rotator is provided through which the write and read beams pass following beam combinations, the optical rotator being driven by a motor to rotate at half the rotational velocity of the drum, and thereby present an image to the optical tape which rotates synchronously with the drum.

Abstract: An arc tube for a high pressure discharge lamp comprises a sealing element displaced from the end and sintered within the arc tube to form an overhung end. An electrically conductive cermet end member has a boss member which fits within a central aperture in the sealing element to thereby centralize the cermet end member within the arc tube. The cermet end member is therefore positioned within the arc tube independently of the arc tube wall and any distortion of the arc tube which has taken place during sintering of the sealing element has no effect. Preferred dimensions of the components are given so that cracking of the cermet end member is avoided and suitable electrical resistance is achieved.

Abstract: An arc tube (13) for a high pressure sodium discharge lamp (10) contains a quantity of a getter materal which comprises an alloy of titanium and niobium metal. The alloy is in the form of a coiled wire (31) which is wound on a tungsten electrode shank (29). The wire may have a sheath of niobium metal.

Abstract: A phosphor comprises a chromium activated alkaline earth aluminate having a hexagonal crystal structure and incorporates divalent europium as a sensitizer. The phosphor may also incorporate one or more of divalent manganese and/or zinc and/or magnesium. Such a phosphor emits in the infra-red.

Abstract: A digital phase-locked loop using a binary overflowing accumulator as a numerically controlled oscillator has external compensation to eliminate frequency-dependent phase offset problems while not requiring any second-order filtering.Operation of the NCO adder initiates with value set by the center frequency control and under the latching action of the latch clocked by the reference oscillator produces a linearly stepped output. Detection of the most-significant bit values produces a square wave at the output. The phase detector latch is used for phase correction, while comparator eliminates steady-state phase error.

Abstract: In double ended high pressure discharge lamps such as are used in sealed beam reflectors the leads pass through the reflector bowl close to the axis thereof and close to each other giving risk of flashover therebetween, particularly with the high voltages required for hot restarting. To reduce such effects at least one of the leads has a length forming part of a circle terminating at one end and a sleeve of insulating refractory material conforming generally to the same circle is fitted to at least part of the circular part.

Abstract: A lighting device includes a light pipe and a tungsten halogen reflector lamp transmitting light beams parallel with the axis of the light pipe. This allows the use of a dichroic filter which provides for an increased transmission whereby low wattage lamps (36 w) can be used instead of the more usual 100 to 200 w light sources. A number of shaped prisms can be used as end arrangements whereby different effects are obtained, for example, bi-directional, omni-directional or angled beams can be provided.

Abstract: A chemical-sensitive semiconductor device in the form of a chemical-sensitive field effect transistor, suitable for testing relatively small volumes of a fluid analyte, comprises a substrate provided with a passageway, interconnecting its major surfaces, along which the analyte can pass. Drain and source regions are formed at opposite ends of the passageway and a chemical-sensitive gate region is formed on the sides of the passageway.

Abstract: A heater comprises a substrate having an electrically-insulative ceramic coating and a heater track deposited on the coating and electrically connected to a power supply via ends. The heater track consists of a composite material having predetermined proportions of a metal and a material capable of undergoing a reversible change in volume at a predetermined phase transition temperature. The change in volume changes the proportions of metal to material and thus changes the resistivity of the composite material, so that the heater can be used as a self-regulating thermal cut-out device by limiting its own heat output to the phase transition temperature.

Abstract: A tungsten halogen incandescent filament lamp is provided having a fill of inert gas and halogen. In such lamps and especially in lamps provided for studio and theatre applications having operating temperatures between 2200K and 3450K there is a tendency to arc over between the filament limbs. According to the invention this problem can be solved by adding hydrogen gas in an amount between 0.05% and 1% by pressure at 20.degree. C. This hydrogen gas is in addition to any hydrogen which is present as part of the halogen or halogens. A preferred halogen is the solid hydrogen, bromophosphonitrile (PN Br.sub.2).sub.n which introduces phosphorus as a getter into the lamp.

Abstract: A lead wire arrangement used in the pinch seal of a tungsten halogen incandescent or air burning discharge lamp. The outer lead wires are made of an oxidation resistant material having a melting point significantly lower than the temperature surrounding the foil and lead wire arrangement during the pinch sealing process. Because the temperature reached during pinch sealing is of the order 2,000.degree. C. conventionally outer lead wires have been made of a highly refractory material, for example, molybdenum which has to be coated with platinum to prevent oxidation. The invention uses materials having significantly lower melting points than 2,000.degree. C. which are also oxidation resistant thus avoiding the use of the expensive platinum. Suitable materials for the outer lead wires include titanium wire, titanium coated wire, nickel/iron alloys and titanium/molybdenum alloys.

Abstract: A projector lamp comprising a single ended metal halide discharge lamp in a generally spherical reflector has been found to exhibit turbulence when running. The resulting fluctuation of light especially when used in conjunction with the reflector to concentrate the light for studio or theatre applications provides an apparent movement which is extremely disturbing to the eye. It has been found the turbulent movement of gas around the electrodes in the lamp envelope can be regularised by the application of a magnetic field to the envelope. The turbulence is sensitive to conditions within the discharge arc tube and the strength and position of the magnetic field has to be variable to cater for this. The magnetic field is conveniently applied by an electro-magnet using lamp current.

Abstract: An infra-red emissive phosphor consists of chromium activated cerium manganese aluminate having a hexagonal crystal structure and represented by the general formula: ##EQU1## where x is from 0.3 to 3.0, y is from 0.01 to 2.0, z is from 0.001 to 0.3 and R is manganese, in which up to 95 atomic percent of the manganese may be replaced by an equivalent amount of zinc or magnesium or both.

Abstract: An incandescent lamp, which emits infra-red radiation, comprises a tubular quartz envelope, within which a tungsten filament is supported. To reflect radiation, which is emitted in a downward direction from the filament, back in an upward direction to an item to be heated, a substantially pure aluminum oxide coating is bonded in a substantially permanent manner to the surface of the envelope. The coating extends subtantially along the length of the lamp and around approximately half of the cross-sectional circumference thereof. The coating is applied to the envelope by a spray gun technique, wherein finely divided aluminum powder is blown through an oxygenated flame, which is directed towards an area of the envelope to be coated.

Abstract: An arc discharge lamp is provided using sealing compositions comprising mainly Al.sub.2 O.sub.3 --SiO.sub.2 --MgO. Preferred compositions include between 25 to 28% by weight of MgO and 13 to 21% by weight of Al.sub.2 O.sub.3 since these have lower melting points than others in the group. The sealing compositions are used to seal end closure members of alumina or cermet to ceramic arc tubes for use in discharge lamps. The compositions are selected to have linear expansion co-efficients compatible with the materials of the end closures and arc tubes. The methods described give sealing times of between 3 and 4 minutes.

Abstract: A discharge lamp is provided with a starting aid in the form of a loop of conductive wire arranged around the discharge lamp arc tube and a novel spark gap. A conductive element is electrically connected between the loop and an insulating sleeve adapted to form a spark gap by means of the conductive element wrapped around an opening in the insulating sleeve. The opening can be in the form of a drilled hole or slot and the arrangement is particularly useful in the restricted confines of a sealed beam reflector lamp.

Abstract: The invention provides an improved method of construction of a prefocus lamp, to improve positioning of the filament relative to the lamp cap, and a lamp so made. The lamp envelope has a pinch seal with V-shaped grooves into which a resilient ring is sprung. This assembly is a sliding fit in the lamp cap and is slid therein to have substantially only line contact between the ring and the cap. The envelope can then be relatively easily rocked and otherwise moved in the lamp cap to be precisely positioned. When the positioning is complete solder previously placed in the cap is melted, the position being such that it flows over the ring and fixes the ring to the lamp cap.