Abstract: Optical four wave mixing is provided by interfering two waves on a liquid crystal layer (1) temperature stabilized just beneath its nematic/isotropic phase change transition temperature. The liquid crystal incorporates a guest dye to absorb the light producing a holographic thermal image which is accompanied by a holographic phase image. Illumination of this phase image with a `third wave` of different wavelength is then used to produce the required holographically diffracted `fourth wave`.

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 array of acousto-electric transducers 1,2, e.g. a hydrophone streamer, is calibrated by disconnecting the common ground wire 17, to which all the transducer shields 14 are connected, from ground and connecting it instead to a local oscillator 18. Test signals from the oscillator are capacitively coupled into each transducer via the inherent capacitances of the insulated lead throughs 15, 16 in the transducer shields 14.

Abstract: Low concentration standard aqueous solution for analytical purposes is prepared from a water soluble glass body containing the standardizing material. The glasses are phosphorus pentoxide based glasses and provide release rates, e.g. of Na.sup.++, of 0.01 to 100 micrograms per cm.sup.2 per hour.

Abstract: A method of bonding a metal body to a ceramic body, particularly a method of bonding a TWT slow-wave helix to boron nitride support rods, involves depositing on one of the bodies an active metal layer, typically of titanium, to be sandwiched between barrier layers protecting it from oxidation. The assembly is formed and then heated to a temperature sufficient to cause the active metal to migrate into the surface of the ceramic, whereupon the temperature is further raised to cause the protective barrier layers to form a braze uniting the metal body to the now-metallized ceramic body.

Abstract: A bipolar lateral transistor is formed in a highly doped p.sup.- -type well (13) the base contained in a lightly doped n.sup.- -type well (12) the collector in a very lightly doped p.sup.-- -type substrate (11). The arrangement is such that the boundary of the collector/base depletion region is distributed so that the non-depleted base region is wide below the emitter but very narrow at the surface. This defines a narrow active base region in the lateral emitter-collector path thus ensuring that the transistor operates predominantly in its lateral rather than its vertical mode. The structure is compatible with conventional CMOS and NMOS processing techniques.

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 dielectric composition comprising a ternary system of non-stoichiometric lead magnesium niobate, non-stoichiometric lead zinc niobate and non-stoichiometric lead iron niobate up to 10 wt % PbO may be added to the ternary mix. Compositions with firing temperatures in the range 950.degree. to 1040.degree. C., have dielectric constants in the range 13,900-22,100 making the composition particularly suitable for high silver content multilayer ceramic capacitors.

Abstract: A multiple output, power inversion adaptive antenna array comprises a number of antenna elements A1-An feeding a cascade beam former structure having groups of decorrelation stages D1.sub.1 -D1.sub.n-1, D2.sub.1 -D2.sub.n-2 etc. The outputs of the first stage in each group are scanned sequentially until the wanted signal is predominant, as determined by a wanted signal recognition CONTROL, at which time scanning of the switch S is halted.

Abstract: In a telecommunication system with a number of units (Ula-Una, Ulb-Unb) for control purposes and also for subscriber facilities, each such unit is duplicated, as is the system controller (SCa, Scb). There are two local area networks (1,3), each of which interconnects one system controller and one unit of each pair of units. When one network is to be isolated, e.g. for servicing or when a fault occurs, its controller detects that condition, and isolates that network by relay circuitry in the termination (T2, T3) of the bus. Another version of the system uses local area networks of the closed ring type. In certain cases the units, etc., may be triplicated.

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 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: 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: 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 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).