Abstract: A radio receiver for frequency modulated signals in which direct conversion techniques are used to provide zero I.F. quadrature baseband signals I & Q. The I & Q signals are limited (11,12) to form square wave signals and pulse forming networks (13,14) derive pulse sequences the frequencies of which represent the polarity changes in the square wave signals. Each square wave is multiplied (15,16) by the pulse sequence derived from the other square wave to produce a unipolar pulse train. The two unipolar pulse trains are combined (17) to give a digital output signal the frequency of which is equal to the sum of the frequencies of the two pulse trains. Low pass filtering the output signal produces a simulation of the original baseband modulation.

Abstract: A magnetic angular position sensor having a ferrofluid filled spherical chamber in a cylindrical housing, within which floats a body comprising a buoyant core carrying a magnet which aligns itself and the body with the earth's magnetic field, and carrying an odd number of small permanent magnets. Hall effect devices are located in recesses in the ends of the housing. The housing also carries a calibration solenoid.

Abstract: A receiver for a Navstar satellite navigation system wherein the satellite signals are down converted into zero i.f. quadrature signals (70a, 70b) and digitized (71a, 71b). The digitized signals address a PROM (72) together with additional bits representing phase rotation information (74) and locally generated code signals (e,l,p). The PROM is loaded with data in the form of "look-up" tables incorporating combinations of all input signal conditions whereby the combined address signals effect correlation and phase rotation simultaneously of the received signals.

Abstract: On line coating of optical fibre (20) adopts silicon nitride or oxynitride to provide an hermetic seal using chemical vapor deposition. Non-contacting gas seals (3,4) at the top and bottom of the reaction chamber are so constructed that fibre vibration is avoided, (6) surface flaws are minimized and the coating minimizes stress corrosion.

Abstract: An optical fibre (1) is provided with a coating (2) which varies in thickness along its length, for use, for example, in optical fibre sensor systems, by applying layer of liquid coating material, and permitting surface tension to cause beading of the coating on the fibre before curing the coating material whereby to maintain the beaded structure.

Abstract: A rod-in-tube method of manufacturing optical fibre where the rod and the tube are fed into the heating zone of a furnace at different rates, the rod feed rate being greater than the tube feed rate. The rod is mounted relative to the tube such as to permit self-centering of the rod in the tube when the tube collapses onto the rod in the heating zone. The drawn fibre may be monitored by means of an in-line fibre core to O/D monitor and feed-back employed to drive the tube and rod feed mechanisms accordingly thereby providing precise control of the core to O/D ratio of the fibre. Very long fibre lengths may be achieved by feeding the rod into the heating zone at a greater rate than a very large mass tube billet and consecutively feeding further rods into the tube billet as the preceding rod is used up.

Abstract: Infrared optical fibres are provided with hermetic coatings (6) by decomposition or reaction of volatile compounds of the coating material at the surface of the fibre. Materials having melting points greater than the fibre's glass transition temperatures may thus be applied at temperatures lower than the glass transition temperatures. The fibre (1) may be sufficiently hot from a preceding fibre formation (2,3) process in line with the coating process to enable the decomposition or reaction, or additional heating of the fibre by radiation may be necessary in the reaction chamber (7).

Abstract: A cable comprises a central electrically insulating composite string, including a relatively hard strength member filament (8) with a relatively soft layer (9) thereon. Four, in the case of a quad, electrical or optical conductors (10) are at least partially embedded in the softer layer (9) and may abut the filament (8). A polyethylene sheath (11) is extruded over the string. The quad may be made by pressing the conductors against the outer periphery of the string whereby to deform it without heating it, and may involve the use of a die arrangement (FIGS. 3 and 4) which ensures the desired spacing and configuration of the conductors relative to one another, necessary for high quality quads of electrical conductors in order to have low crosstalk, is obtained. The cable construction, which facilitates miniature quad manufacture, is such that cable can be manufactured with a minimum of process stages at high throughput speeds.

Abstract: An accelerometer comprises a quartz beam 1 having on its upper and lower faces surface acoustic wave devices 2, 3 and 2', 3'. The beam is centrally mounted on quartz spacers 4, 5 which have metallized contacts for the lower SAW device. The spacers are carried on a quartz substrate 6 which is supported on a header 7 forming the base of a dual-in-line package. Mass-loading 8 is provided on each end of the beam 1.

Abstract: A method of making a single mode optical fibre directional coupler in which a pair of fibres (30,31) in side-by-side contact is subjected to a succession of drawing operations produced by traversing the fibres longitudinally through a flame (34) while stretching them between a pair of carriages (32,33) driven at slightly different speeds.

Abstract: A Hall effect device for responding to weak magnetic fields uses a small chip of gallium arsenide located between the overlapped ends of two flux concentrators. The spacing between the concentrators may be as small as 95 micrometers. The flux concentrator, which serve to enhance the device's sensitivity are made of amorphous magnetic material, i.e. a metallic glass, which has high permeability.

Abstract: A device for the controlled release of an active material into an aqueous medium comprises a porous sintered body of a water soluble glass (11). The pores of the body are filled with a composition (12) consisting wholly or partially of an active material. The device may be provided with a low solubility coating (13). On immersion in an aqueous medium the glass (11) dissolves to become a sponge-like structure having a plurality of convoluted capillaries and from which the active material is released.

Abstract: The cells of a static random access memory have a diagonal of `dog leg` structural layout. This permits the use of straight word lines of low impedance and hence of low time constant. Advantageously the work lines are of polysilicon thus permitting a compact design.

Abstract: Insulation flaws in electrical components are detected by measurement of electrical leakage before and after immersion in a mobile ionizing solvent, e.g. a lower alkyl alcohol. A significant increase in leakage is indicative of a flaw, e.g. a crack in the insulation.

Abstract: An energy efficient output circuit for a static random access memory includes a pair of output transistors each driven by a bootstrapped driver stage. This requires less current than conventional amplifier chain.

Abstract: In a small business-type telephone exchange, calls are set up in TDM manner using PCM to convey speech and data if the exchange serves any data terminals. The exchange has subscriber line ports (SLC) each serving two lines and a smaller number of trunk line ports (TLC) each serving a trunk to a local exchange. Each port has a local processor (SIP) with analogue-digital and digital to analogue conversion circuitry (CODEC-FILTER-TSAC). The exchange also has a central processor (CCP) with its associated memories (ROM, RAM, EAROM).The ports and the central processor are interconnected by an intelligence bus (PCM BUS) and a signalling bus (SIG BUS). The central processor (CCP) and the port processors (SIP) co-operate in call setting with all communications between the processors over the signalling bus. During operation the central processor (CCP) polls the ports via the signalling bus (SIG BUS) for ports needing the services of the central processor and also to pass call control information to those ports.

Abstract: Printed circuit manufacture may employ a plated palladium-nickel alloy layer as an etch resist and plating finish. Prior to the use of palladium-nickel, tin-lead was used as the etch resist and plating finish. The palladium-nickel layer is generally superior to the corresponding tin-lead layer except for solderability. To improve the solderability of at least these areas of the palladium-nickel to which elements are to be soldered, a layer of copper is deposited thereon. If desired, the solderability of the copper may be preserved by coating it with, for example, a tin-lead layer.

Abstract: A demodulator logic for FSK signals on an RF carrier in a direct conversion radio receiver, wherein the received signals are mixed with a local oscillator to provide quadrature baseband signals, characterized in that the demodulator logic comprises two clocked D-type flip-flops, FF1,FF2 one baseband signal being applied direct to the clock input CK of one flip-flop and inverted to the clock input CK of the other flip-flop, the second baseband signal being applied to the D inputs of both flip-flops, one input Q from one flip-flop being algebraically combined with one output Q from the other flip-flop to provide a demodulator signal output of the receiver, the two flip-flop outputs being chosen so that for a given FSK value they always have the same logic value.

Abstract: Lead-less tantalum capacitors are made using a lead frame (1) formed to provide connection terminals (3,4) separated by an H-shaped aperture (7) and a bent-up anode support station (5). A two-part mould (13,13a) is used to injection mould plastics around the capacitor bodies prior to detaching the capacitors from the lead frame by severing necks (15,16,17,18).A second embodiment has flat connection terminals which are bent around the encapsulated body.