Abstract: Apparatus for selectively coating part of a member with a material, such as plating the walls of a hole in a printed circuit board, may include two heads which, during operation of the apparatus, form a passageway between them through the hole. A pump alternately sucks and pumps liquid used in laying down the coating in both directions through the hole. Electrodes may be included in the heads to permit electroplating techniques to be applied in laying down the coating where the material is metallic.

Abstract: An electrical power measuring device wherein signals (V.sub.i, V.sub.v) representing one of the current and voltage supplied to a load are applied to the input of a sigma delta modulator (9), and the state (0 or 1) of the modulator output together with the polarity of the other one of the voltage and current values, is used to determine the sense in which the digital signals representative of successive samples of the other one of voltage and current values are accumulated in an accumulator (11). The count in the accumulator (11) consequently increases at a rate representative of the power supplied to the load.

Abstract: Semiconductor apparatus comprises a split-gate semiconductor device (1) which has a first layer (3) of a first undoped semiconductor material (e.g. GaAs) and a second layer (4) of a second semiconductor material (e.g. AlGaAs) which is doped through at least part of its thickness. The second material has a higher energy band gap than the first material, and the layers form a heterojunction so that electrons from the second layer collect in the first layer to form a two-dimensional electron gas. Drain and source contacts (7,6) are provided on the second layers, and a gate electrode (8) is so configured that on application of a sufficiently large negative bias to the gate electrode a constriction is formed in the first layer through which only a one-dimensional electron gas can pass between the source and drain contacts. The apparatus also includes a bias supply (17) for applying a bias voltage between the source and drain contacts. The source/drain bias is made equal to or greater than E.sub.f /e where E.sub.

Abstract: In a process for mass producing optical storage sheets, an elongate film of a liquid crystalline material is fed lengthwise along a path through an aligning gate. The aligning gate applies to successive areas of the film a field which aligns the molecules. The field may be an electric field and/or a shear field. An aligning layer, such as a surfactant layer may also be used for alignment of the film areas. The aligned film may then be cut into pieces for use as microfiches or microfilms. The film material is preferably a liquid crystal polymer material.

Abstract: A method of making material in the form of a fine wire or thin strip or sheet suitable for use as electrical conductors comprises: forming an ingot substantially consisting of an alloy of gold and one or more of the metals titanium, lutetium, zirconium, scandium and hafnium, the amount of the or each of said one or more of the metals in the alloy lying in the range from substantially 0.1 at % to an upper limit comprising the atomic percentage of that metal corresponding to the maximum solubility of that metal in the alloy; solution heat treating the ingot and then quenching the ingot from the solution heat treatment temperature; mechanically working the ingot to have a maximum dimension in at least one direction of not greater than 250 .mu.m; and heat treating the resulting material at a temperature below its solvus temperature from an ambient atmosphere containing oxygen and/or nitrogen in the ambient atmosphere.

Abstract: In order to deposit films of materials, such as polysilicon or silicon dioxide, on major surfaces of substrates by a low-pressure chemical vapor deposition (LPCVD) process, gas, such as a silane gas, is admitted to a chamber at one end and is pumped through the chamber by a pump. The substrates are mounted such that the general direction of gas flow is perpendicular to the substrate major surface, and are heated to cause reaction of the gas to form the required film. In order to achieve uniformity of the deposited films over a number of substrates, the pressure in the deposition chamber is maintained below 10m Torr.

Abstract: A tunable laser having a range of possible emission frequencies has a Bragg cell mounted inside its laser cavity such that only light passing through the Bragg cell without Bragg deflection will be emitted by the laser.

Abstract: In order to control the brightness of a fluorescent liquid crystal display, a photodiode is located adjacent an edge of a display cell. The photodiode receives light which has been totally internally reflected within the cell and which is thereby emitted from the cell edge. The emitted fluorescence remains subtantially constant during switching of the display and is a measure of the brightness of the display. The output of the photodiode is fed to a circuit which controls the brightness of the light source illuminating the display, so that a substantially constant display brightness is obtained.

Abstract: A deposition process includes the steps of heating a substrate, and passing silane gas over the substrate such that the heated substrate causes decomposition of the silane gas thereby to cause deposition of polysilicon film on the substrate. The temperature of the substrate and the pressure of the silane gas are controlled so as to increase the grain size of the deposited films.

Abstract: A position measurement system transmits moving interference pattern and these are received by a sensor fixed relative to the transmitter and a mobile sensor, by comparing the phases of the interference pattern at the two sensors the position of the mobile sensor relative to the transmitter can be calculated.

Abstract: An optical switch apparatus comprises two optical waveguides, which may be formed by diffusing titanium into a lithium niobate body. Electrode are bonded to the surface of the body and are arranged such that an electric field may be applied across the body, resulting in the distance between the waveguides being reduced. Hence a change is produced in the coupling constant of the waveguides and the switching response of the switch may be enhanced.

Abstract: A polarization controller comprises at least one stack of nematic liquid crystal cells arranged such that radiation incident on the stack will pass through each cell in the stack in sequence. Synchronized electric or magnetic fields are applied across the cells so as to change the phase retardation of the radiation transmitted through each cell by a chosen amount, the optical axes of the cells being oriented with respect to each other such that the polarization of radiation incident on the controller is caused by the controller to change from a first state to a second state.

Abstract: In a guidance system for guiding an automated vehicle around an area such as a warehouse, a scanning laser beam from a source mounted on the vehicle impinges upon reflectors located around the area. Each reflector incorporates an optical code which identifies that reflector. Laser light reflected back to the vehicle from the reflectors is used to control the movement and heading of the vehicle. The area is divided notionally into a number of equal sub-areas of predetermined dimensions, each having at least two differently-coded reflectors. The vehicle is first moved to a position from which it can scan initialization reflectors located at selected initialization positions.

Abstract: Many housings for electronic devices require to be carefully sealed, as well as incorporate heat sinks for the electronic devices. Careful sealing has required expensive machined housing joints and, because electronic devices may be misaligned to the substrate, rounded heat sinks have been used, giving restricted contact areas and hence limited cooling. The invention employs a thermally conducting flexible membrane capable of being urged into thermal contact with the electronic device, for example by a evacuation of the housing, thereby permitting a simple hermetic seal as well as contact with the electronic device over a large area.

Abstract: A device for indicating whether a rise in temperature above a predetermined value has occurred includes a support member, such as a label, on which a temperature-sensitive material is deposited. The material includes a large number of fracturable microcapsules containing a medium which changes from a solid state to a liquid state at the predetermined temperature value. The viscosity of the medium in its liquid state and the material of the support member are chosen such that the distance d.sub.1 by which the medium flows across the support member after the fracturing of the microcapsules so as to activate the device is indicative of the time between activation of the device and cooling of the device to below the predetermined temperature value. If the temperature is subsequently allowed to rise above the predetermined value, the medium will again assume its liquid state and will flow further across the support member, reaching a distance of, say, d.sub.

Abstract: A delta sigma modulator arrangement in which non-ideal characteristics such as noise or offsets in amplifiers or other circuits of the circuits of the arrangement are compensated by chopper stabilisation.

Abstract: A triplate fed slot antenna in which a conductive sheet has a slot with a length of .lambda., where .lambda. is the wavelength of a signal intended to be radiated from or received by the antenna. A triplate feed structure is coupled for feeding the slot. The triplate feed structure includes two outer conductors defining walls of a resonant cavity backing the slot, and an inner conductor disposed in the cavity.

Abstract: In a method of forming a field-induced emission device, a cathode is provided on a substrate, for example by etching away the substrate to leave a pointed projection. The projection may be covered with a metallic layer to enhance the field-induced cathode emission. A first insulating layer is formed over the substrate, with an aperture therein corresponding to the cathode position. An apertured control grid layer is formed over the first insulating layer and an apertured second insulating layer is formed thereon. A tunnel formed by the apertures in the insulating and conductive layers is filled with a plug of soluble material. An anode strip is formed on the second insulating layer and over the plug, and the plug is then dissolved through gaps at the edges of the anode strip, thereby leaving an unsupported area of anode strip over the cathode. The tunnel may then be evacuated or may be filled with gas and the gaps at the edges of the anode strip will then be sealed to retain the vacuum or gas.

Abstract: An antenna capable of producing circularly polarized radiation is formed by two non-coaxial cross dipoles.

Abstract: A superconducting electronic device utilizes a weak link (Josephson junction) between two regions of superconductor material. A method of making such a device having a granular structure consists of taking a substrate with a predetermined grain size, and forming a thin film of superconducting ceramic upon it. The film adopts the grain size and structure of the substrate, and the film is then processed to form two relatively large areas of granular film connected by a thin link which contains a single grain boundary which acts as the weak link.