Abstract: A cable grip device, known as a "stopper", suitable for holding submarine cables during laying and recovery operations on board a ship, comprises a conventional helically wound stopper modified to have a low coefficient of friction over an internal surface portion (1A) and a higher coefficient of friction portion over a surface (1B), which it is found enhances the tensile load which the stopper can bear particularly when used for smooth surfaced deep water submarine cables.

Abstract: A data processing arrangement intended for use, inter alia, in a multi-processing system for use in association with a systolic array is implemented on a single semiconductor chip. The arrangement includes processing means (AU, MU) and storage means (ACC), interconnectable via an electronic equivalent (MM) of a cross-bar switch.

Abstract: A coupled waveguide injection laser is provided with two waveguiding ridges (36,37 or 60,61) that are configured such that the coupling between them produces a first order supermode for which a signal current modulation produces optical amplitude modulation with substantially no attendant frequency modulation. In a related structure the configuration affords the facility of providing for the zero order supermode optical frequency modulation with substantially no attendant amplitude modulation.

Abstract: A multichannel automatic remote line testing system enables telephone lines connected to a common highway to be individually tested from the exchange. Pulse code modulation of an audio tone provides address codes which are checked by the remote line testers and responded by the tester whose programmed address corresponds to the particular code sent. Validation circuits check the frequency, encoding and duration of the command.Pulse Code modulation echoes are used to confirm interactive operation.

Abstract: A strain or pressure responsive transducer comprises a pair of elongate beam resonators arranged end to end and provided with a flexible coupling therebetween. The arrangement oscillates e.g. in a double see-saw or butterfly mode. The transducer is disposed on a diaphragm whereby strain may be transmitted to the oscillatory system. The frequency of oscillation is a function of this strain.

Abstract: A distributed feedback (DFB) laser having a divided electrode structure on one surface by means of which the injected current distribution in the laser may be modified so as to enable independent control of laser output amplitude and wavelength.

Abstract: A telephone exchange, now often called a switch, includes a switching network of the space division type which switches PCM highways, and includes a number of sub-networks (SEG1, SEG2 . . . SEGN) each of which is a plural (e.g. three) stage array. When a call is to be set up it is set up via one of these sub-networks, and a reserve path chosen for it through a different sub-network. The identity of this reserve path is noted in memory for use if the path via which the connection is actually set up fails. If that happens the call switched to the reserve path. This facility can also be used for "block transfers" of all calls in a sub-network, e.g. when the latter is taken out of service for maintenance. In one embodiment in which three stages are used, part at least of the middle stage is common to all sub-networks. Such an apparently large amount of switching corss-points is not too "cost ineffective" since the switching sub-networks are made up of relatively cheap VLSI units. Since the physical paths are e.g.

Abstract: An automatic telephone exchange, such as a PABX, includes a number of group control units (GCU1 to GCU4) each of which is a simplified version of the system of U.S. Pat. No. 4581733. These are connected via respective PCM highways to a central switch, which is an electronic time space switch, and a central controller. The central controller does the major part of the call setting and control, all calls being set up via the central switch.

Abstract: A sequential decorrelator arrangement for an adaptive antenna array comprising a plurality of antenna elements the outputs of which feed a cascaded beamforming network having a succession of stages, each stage having one less decorrelation cell than the preceding stage and the first stage having one less cell than the number of antenna elements.The network includes means for applying weighting to the signals applied as inputs to the cells of at least the first stage. The decorrelation cells in each stage comprise means for applying simple rotational transforms to the input data in accordance with a weighting factor common to all the cells in a stage, each stage further including means for deriving said weighting factor from the weighting factor deriving means of the previous stage and the output of one cell of the preceding stage. Each stage includes means for scaling the output of each cell in the stage by a scaling factor calculated from the weighting factor deriving means of the stage.

Abstract: A method and apparatus for effecting phase rotation of a digital signal by applying said digital signal as partial address signals for a look-up table in a memory together with rotation control signals forming additional address signals whereby the memory output represents the phase rotated signal, characterized in that each input vector is modified so that points representing digitized input vector values plotted on a rectangular coordinate grid are transformed to lie on an alternative coordinate system and the rotated vectors are retransformed and requantized to a digital output.

Abstract: A cavity backed crossed slot antenna wherein the cavity depth d is less than one eighth of the operating wavelength .lambda. at the lowest frequency of operation, the major dimension a of the cavity in the plane of the slots is less than one half of the wavelength .lambda. at the lowest operating frequency, and the slots are excited by four symmetrically located capacitive coupled feed probes.

Abstract: A telephone instrument has a rectangular recess (3) along one side of the body which receives the handset. The handset has a recess which fits over a locating member (2) when on-hook. The hook switch contacts (6) are controlled by a pivoted member (4), which acts on the end of a plunger (7) to control the hook-switch contacts. The plunger (7) is spring-urged to its off-hook condition, i.e. when the handset is not in the recess.

Abstract: In the manufacture of high quality optical fibre for telecommunications, a preform (1) is advanced towards a furnace (9) until a tip detector (5) automatically stops the preform (1) at a predetermined position (11) in front of the furnace to provide a reference datum for a second mode of operation in which the computer (12) can be initiated manually (12B) to advance (4) the preform (1) by a predetermined amount into the furnace to commence drawing the optical fibre. Preferably the tip detector is a paddle (6) pivotally mounted (7) and operates an optical sensor (8).

Abstract: An alloy, e.g. an aluminum/silicon or aluminum/copper alloy, incorporating an anodizable and non-anodizable phase is selectively etched to remove the non-anodizable phase from the surface. The surface is then anodized to provide a continuous oxide film, e.g. to impart wear resistant properties to the surface.

Abstract: A fused tapered optical fibre directional coupler for use in a polarisation-preserving fibre system has a short stub length of non-polarisation-preserving fibre spliced into each fibre from which the coupler is made. The reduced diameter and tapered portions of the coupler are confined to the stub lengths since it is found that low loss coupling is not achieved if these portions are fabricated in fibre with a polarisation-preserving structure.

Abstract: Bistable operation of ferroelectric liquid crystal smectic I* or smectic F* display cells is disclosed which uses a greater liquid crystal layer thickness than is achievable with smectic C* material while yet retaining bistability of operation.

Abstract: An adaptive antenna array arrangement for a receiver in a frequency hopped spread spectrum system. The arrangement includes an auxiliary local oscillator (lo.sub.a) which is hopped sequentially and pseudo-randomly across the spread system independently of the main frequency hopped oscillator (Lo.sub.m). The adaptive array processor (FUA, FM, PM) is digital, operates in an open loop configuration and evaluates the frequency bands during periods of time when the main oscillator is not operating in those bands. The processor derives null sterring weights for each band. The weights for each band are stored (WS) and subsequently used (W.sub.In -W.sub.Qn) when the main oscillator hops into the band and so cause the array of generate nulls directed towards sources of unwanted systems.

Abstract: Phase rotation of an input digital signal is effected by applying the input signal to a look-up table in a memory together with a rotation control signal. The output of the memory is the phase rotated signal. To reduce the size of the PROM required for the look-up table advantage is taken of the symmetry of the quadrants through which the signal may be rotated. With a maximum 0.degree. to 360.degree. phase rotation range divided into four 90.degree. quadrants a look-up table is only required for one quadrant. Thus the quadrant which the input signal is in is determined and the input signal transformed to correspond to the one quadrant by simple logic external to the PROM.

Abstract: A power component such as a power transistor is mounted on an insulating substrate of, e.g., beryllia by using a thick film deposition technique. A first layer (2) is deposited and a second layer (3) is deposited over the first layer to produce a regular series of troughs and lands, in the preferred embodiment troughs and ridges, whereby voiding in the solder bond is minimized if not eliminated to thus maintain a good thermal conductivity between the component and the substrate.

Abstract: Optical fibre (4) is drawn from a preform (1) by a capstan (5), and a control circuit (22) drives the capstan and the preform at respective predetermined rates during ramp-up. The capstan drive rate is modified (controller 31) in response to deviations from the nominal fibre diameter as measured by a fibre diameter monitor (9) over short-term periods, and the preform feed rate (20) is modified (algorithm 21) to maintain an average fibre pulling rate within .+-.5% of the present pulling rate, to thus control the glass melting rate.