Abstract: An optical fibre reflectometer in which the end of the optical fibre 4-port coupler for optical coupling to test fibres is not protected from damage by the use of a sapphire window because of the problems of unwanted reflections that this engenders. Instead the end is coupled to the test fibres by means of a replaceable slug (33) containing a stub length of fibre (20). This fibre stub (20) is intrinsically just as susceptible to cumulative damage when test fibres are repeatedly butted against its end, but it protects the coupler because it is itself butted against the coupler only once in its life. When the cumulative damage becomes excessive the slug can be replaced more simply and cheaply than replacing the whole coupler.

Abstract: A solid-state heading sensor is comprised by a three-axis Hall effect magnetometer and a three-axis accelerometer. The magnetometer is comprised by a cube-like structure (10) of non-magnetic material on each of three orthogonally related faces of which is located a respective Hall effect device (11, 12, 13), for example of GaAs. The three-axis accelerometer may be comprised by a three-axis module (15) disposed in a recess in the cube-like structure, or by three separate accelerometer structures (23, 24, 25), for example planar etched silicon accelerometers, each disposed on a respective one of the orthogonally related faces adjacent the Hall effect device (20, 21, 22) thereon.

Abstract: The strength members of the optical fibre cables to be jointed comprise inner and outer layers of high-tensile wires (9, 10; 9', 10') arranged on respective pressure-resistant tubes (5; 5'), each containing an optical fibre package (not shown). The strength members are jointed by trapping the wires between a quill (15) and a ferrule (16) pressed towards the quill. The quill (15) is of a relatively hard steel and serves to partially reinstate the pressure tube between the ends of the cables, whereas the ferrule (16) is of a relatively soft steel. For jointing of two dielectric covered elements the ferrule is subsequently encapsulated in a dielectric moulding (27). A thin-walled reinstatement tube (17) is arranged between the quill (15) and one tube (5'). The cavity in the reinstatement tube (17) is larger in diameter than the cavity in the tubes (5 and 5').

Abstract: A NAVSTAR receiver in which the received signals are processed to produce digitized quadrature signals at zero i.f. Baseband phasor rotation to effect Doppler tracking in the receiver loop is accomplished by deriving digital signals representing sin .omega.T and cos .omega.T for the required rotation angle .omega.T, multiplying the quadrature signals separately and summing the outputs according to the algorithm I.sup.1 =I cos .omega.T+Q sin .omega.T and Q.sup.1 =Q cos .omega.T-I sin .omega.T, where I & Q are the digitized quadrature signals.

Abstract: An arrangement for digital multiplexing onto a common highway a plurality of analogue input signals which are physically spaced apart over a distance. m time division multiplexing units 5a each have for each of n separate analogue signals n single channel pulse coding means 6 the outputs of which are time division multiplexed at a common outlet 12. Each multiplexing unit 5a also has a timing circuit 7 which can be either free running or locked to the similar timing circuit of a succeeding unit (5b). Each unit has (m-1) bypass connections 15, 16, 17 so that the multiplexed outlets of succeeding units are fed in parallel to a group multiplexer. The timing circuits, being cascaded, ensure that propagation delays for the digital signals from each of the n analogue inputs are obviated.

Abstract: An optical matrix-vector multiplier for multiplying an m-row n-column matrix by an n-component vector to form an m-component vector (FIG. 1). In the specific case of a 3.times.3 matrix (FIGS. 4a and 4b), the multiplier comprises three light-emitting devices (21,22,23), for example LEDs, each emitting at a different wavelength (.lambda..sub.1, .lambda..sub.2, .lambda..sub.3), an acousto-optic modulator (29) driven by each x value in turn, and three integrating photodetectors (32, 33, 34) each receptive to a respective one of the different wavelengths. A single collimating lens (30) serves to apply light, emitted by each of the LEDs in turn in response to respective matrix components, to the modulator (29). The LEDs may be connected by respective optical fibers (24, 25, 26) to a fiber coupler (28) and thence via a common optical fiber (27) to the lens (30), or coupled by a dispersive element (35--FIG. 5) to the lens (30).

Abstract: A moving coil capsule for a telephone handset is designed for high speed mass production. It consists of a carrier ring (1) and diaphragm (2) formed as an interim sub-assembly in a first buffer store. A coil (6) preparation and finishing stage applies the coil (6) on a former in the form of an aluminium dome (5) and inserts the dome (5) into a nest (7) in the diaphragm to form a first sub-assembly in a second buffer store. A magnet assembly (10, 11 and 12) is manufactured using quick curing glue with the outer pole piece (12) formed by an accurate stamping whose outer rim fits precisely in a reference datum (1a) in the carrier ring.The interim sub-assemblies and magnet assemblies are made one at a time, and the first sub-assemblies are formed two at a time from the interim sub-assemblies, but at half the speed.Final assembly of the magnet assembly and first sub-assembly together with a rear cover (14) is carried out and a throughput at a rate of one capsule in less than four seconds can be achieved.

Abstract: A vehicle tracking system for determining the lateral position of a moving vehicle relative to an optically distinct line extending along the roadway on which the vehicle travels. A camera periodically scans the roadway including the optically distinct line thereon. Signals representing successive scans are stored then correlated to determine the lateral movement of the vehicle between scans.

Abstract: In an NOR decoder for a static random access memory the individual transistor gates (30) are coupled to metallization tracks (31) via polysilicon contact islands (33). The gates of selected transistors are divided into two portions (20a, 20b) disposed on diametrically opposite sides of the corresponding islands (33). This arrangement allows a closer spacing of the tracks (31) than is achieved in conventional layouts.

Abstract: A structure of photodetector in which the active region is formed by creating a p-n junction (6) extending in a layer (3) of material of small band gap (InGaAs) in such a way that it emerges in material (InP) of a larger band gap (2) at the surface of the semiconductive body.

Abstract: A differential surface acoustic wave (SAW) accelerometer comprises a resilient beam 1 one end of which is clamped in a support 2. Opposite faces of the beam are provided with SAW transducers 3, 4 and 6, 7 which respectively form delay lines driven by oscillator 5. Means are introduced for setting the beam into a low frequency mechanical flexural oscillation. The two outputs are connected in antiphase so that under conditions of no acceleration null points in the output waveform will be equally spaced. During acceleration the time intervals between successive nulls will become unequal.

Abstract: In a submarine cable optical fibre regenerator housing a copper tail pipe (optionally with a brass end section incorporating an anti-extrusion profile for fitting inside a gland) is provided with a tight fitting length of thermoplastics sleeving by collapsing a thermoplastics preform down onto the tail pipe using heat and air pressure applied to the outside of an elastomeric tube into which the tail pipe and preform have been inserted.

Abstract: A variable-temperature pressure coating system for optical fibres, particularly for uv-curable primary coatings, includes a gas cylinder (8) for pressurizing a tank (1) of coating material, and a heat exchanger (15) controlling the temperature and thus the viscosity of the coating material supplied to a die chamber (19) through which an optical fibre (18) is passed following drawing. The temperature of the die chamber may also be controlled by the same circuit as the heat exchanger. A valve (14) serves to control flow to the die and to enable priming of the tube (13) by filling with coating material (and removal of air bubbles) prior to supply thereof to the die chamber (19). The system is designed for ease of operator handling together with production of high quality coatings at high speed.

Abstract: A fibre optic lightweight submarine cable (2) is terminated to a tail cable (4) and anchored to a repeater housing (9) with preformed high-tensile steel anchor wires (1,3). The wires are clamped at one end (10) between a collar (7) and frusto-conical clamping segments (11) and strapped at the other end with binders (14). Over the tail cable portion is a spring (6) located on ferrules (6A, 7A) and acting to prevent the anchor wires crushing the tail cable (4).

Abstract: An armored submarine cable joint comprising a tubular housing with internally tapered end portions closely fitting the outer sheath of the submarine cable wherein the armoring wires or tapes adjacent each cable end are splayed and deformed within each tapered end portion. The housing is fabricated from glass filament wound epoxy resin material. The completed joint is potted with a filled epoxy resin system.

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: 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: 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: 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.