Abstract: A frequency synthesizer of the fractional N type comprising a primary voltage controlled oscillator for producing an output signal which is afforded to a phase detector via a divider to provide a control signal for the primary voltage controlled oscillator in the presence of a phase difference between a reference signal from a reference source and the signal afforded thereto from the divider, the division ratio of which may be varied in a fractional N mode to vary the frequency of the output signal in frequency steps smaller than the frequency of the reference signal and wherein a ripple signal tending thereby to be produced and causing frequency modulation of the output signal is compensated by a phase modulator, arranged to couple the divider and the phase detector and to receive a drive signal in antiphase to the ripple signal, wherein the synthesizer further comprises a subsidiary phase lock loop arranged to provide an enhanced representation of the ripple signal in dependence upon the signal afforded to

Abstract: An adaptive line hybrid for digital telecommunications including a bridge circuit for connection to the telecommunication line the bridge circuit having automatically adjustable components in two arms of the bridge to compensate for variations in the characteristics of the telecommunications line.

Abstract: A transistor having a support substrate of semiconductor material and continuous elongate electrodes--a source electrode a drain electrode and a gate electrode. Gain improvement is achieved by dividing the structure into active and passive sites and by providing inductive coupling to supply power feedback to the gate electrode and thereby to sustain and enhance guided wave propagation. At each active site, protrusions extend from the source electrode, and protrusions extend from the drain electrode. The parasitic capacitance at each passive site is thus minimized. The source and drain protrusions are connected by channels in the underlying semiconductor substrate and the conductivity of these channels controlled by gate operation. The drain electrode has a meander configuration to provide inductive coupling to the gate electrode and balance the waves on drain and gate. To reduce resistive losses, the gate electrode is of larger cross-section at passive sites.

Abstract: A temperature measuring arrangement including a relatively long optical fibre temperature sensor doped along its length with material that absorbs light in dependence upon temperature, launcher for launching into one end of the temperature sensor fibre contemporaneous light pulses of two different wavelengths and comparator for comparing variations with time in back-scattered light of the two different wavelengths returned along the sensor fibre in order to provide an indication of the temperature distribution along the fibre, the two wavelengths of the light pulses launched into the fibre sensor being chosen so that they correspond with different absorption bands of the doped material.

Abstract: An antenna suitable for the generation of a circularly polarized annular radiation pattern comprising a substrate spaced apart from a ground plane by a layer of dielectric material, the substrate being arranged to carry on one side thereof a conductive layer in which a plurality of radial slots is defined equiangularly disposed to extend outwardly from a central region of the substrate, and on the other side thereof a microstrip feed line arrangement via which the radial slots are arranged to be fed with microwave energy for the generation of a horizontally polarized radiation pattern and via which an edge slot defined between the peripheral edge of the layer and the ground plane is arranged to be fed with microwave energy for the generation of a vertically polarized radiation pattern whereby the horizontal pattern and the vertical pattern in combination afford the circularly polarized annular radiation pattern.

Abstract: The invention relates to an adaptive cancellation bridge circuit (ACB) for use in a single medium full duplex line termination equipment such as modems where signals are transmitted and received simultaneously along a pair of wires, the transmit and receive signal being separated in frequency. The bridge comprises a bridge network including transconductance cells (TC1, TC2 and TC3), to provide resistive, capacitive, and inductive components and these cells are electronically controlled by a current control device CC driven from a received signal (RXS) inphase and quadrature components to adjust the bridge network so that it becomes balanced and cancels a transmit signal (TXB) completely.

Abstract: In a telephone key system including a central branch exchange and a plurality of key stations, each key station includes a switch-mode power supply unit and derives logic circuit drive power by converting unregulated high tension d.c. voltage power from the exchange to regulated low tension logic level voltage. In the preferred arrangement each key station includes WAL II code signalling receive and transmit circuits and burst mode signalling is adopted. The transformers of these circuits are center-tapped for transformer phantom coupling to the switch-mode power supply unit, and are connected to the exchange by a 2-way 4-wire line. The switch-mode power supply unit is preferably of flyback configuration and includes thus a controlled transistor switch, a transformer, a rectifier, and a switch-mode power supply controller to control on/off operation of the switch for voltage regulation.

Abstract: A multiplex optical sensing system comprises an optical fibre arranged to be subjected at the longest length to fibre deforming forces during operation of the system and means for producing a plurality of pulse trains of coherent light in which the frequency of frequencies of (F1+.DELTA.F1), (F2+.DELTA.F2), (F3+.DELTA.F3) of the pulses in respective pulse trains lie within a different frequency channel for transmission along said optical fibre.

Abstract: A system for multiplexed transmission of different wavelengths of light comprises an array of at least two light sources whose images are formed on the end of an optical fibre. The images have displaced spectra so that a different part of the spectrum of each light source is imaged on to the end of the optical fibre and each part is transmitted by the optical fibre. The images themselves may be displaced by displacing the light sources. A number of such arrays having light sources with emission spectra centered on different wavelengths may be used to increase the number of multiplexed transmission channels.

Abstract: A diamond heatsink assembly for small electronic components such as microwave or millimetric wave devices comprises a frusto-conical shaped diamond held on a support by a clamping member with a part-conical hole through it. One or both of the support and the clamping member are made of a high thermal conductivity metal such as gold, silver, copper or aluminum. The clamping member may be secured to the support by soldering, friction welding, a screw thread or any other suitably tight clamping method. The diamond, the support and the clamping member may be metallized to reduce electrical skin resistance. The arrangement is an improvement on diamond heatsinks in which a diamond is simply bonded to the support by soldering or brazing and heatsinks in which the diamond is pressed into the surface of the support.

Abstract: An optical receiver comprises a local oscillator which produces an output signal having a frequency which differs by a predetermined amount from the frequency of an incoming phase-modulated coherent light signal having a "1" and "0" signal bits, mixing means for mixing the local oscillator output with the incoming signal and switching means effective for switching the mixed signal to respective detectors and the mixed signal frequency whereby the major proportion of the power content of the mixed signal during a "1" bit period is fed to one of the detectors and the major proportion of the power content of the mixed signal during a "0" bit period of the mixed signal is fed to the other detector.In an alternative arrangement the output from the local oscillator is phase-modulated at the intermediate frequency before the mixing operation.

Abstract: A variable timing power storage arrangement for pre-setting a time interval between launch of a projectile and the initiation of a particular function or functions of said projectile and for storing power required inter alia for the initiation of said function or functions at the expiration of said interval, the arrangement comprising inductive coupling means for establishing before launch of the projectile an electrical coupling path between the projectile and control means associated with projectile launching means, signal generating means associated with the control means for generating a train of tone-burst modulated pulses for transmission over said inductive coupling means to the projectile, rectifying means in said projectile for rectifying the pulses of said train the first of which is utilized for charging up power storage capacitor means in the projectile to provide a d.c.

Abstract: An arrangement for suppressing amplitude variation in FM signals comprises a frequency divider which frequency divides an incoming FM signal to provide frequency divided signals having two discrete levels dependent upon the amplitude of the incoming FM signal in relation to a threshold value, and a frequency multiplier which combines the frequency divided signal to provide an output signal of substantially constant amplitude and having a frequency equal to that of the incoming signal.

Abstract: An optical sensing arrangement suitable for the detection of acoustic waves and/or temperature or magnetic field changes, comprises a laser light source for producing polarized light which in operation of the arrangement will be applied for detection purposes to the input end of an optical sensor for transmission therethrough, whereby a relative phase delay is produced between orthogonal components of the polarized light at the output end of the optical sensor, characterized in that a relative phase delay compensation device is optically coupled to and so orientated with respect to one end of the sensor, that the relative phase delay between the orthogonally polarized components transmitted through the compensation device and the corresponding relative phase delay of these components in the optical sensor are mutually opposite, thereby reducing the noise content of an output signal derived from the arrangement and fed to polarization analyzer for producing an indication of structural changes which have occurr

Abstract: A method for accurately aligning an optical fibre with a light source comprises firstly approximately aligning the axis of the fibre with the source (e.g. a laser) and locating two prismatic elements between the end of the fibre and the source. On or both of the prismatic elements is then moved to focus the image of the light source on to the end of the fibre and secured in position. The method can be described as an "Optical lever" as the movement of one of the prismatic elements causes a much smaller movement of the image and the method is thus very accurate. The prismatic elements can be any transparent members which produce an output beam which is angularly displaced from the input beam such as conventional prisms, gratings, diffused lenses or weak decentered lenses. Preferably they are cylindrical transparent rods with one end of each arranged at an acute angle to its axis.

Abstract: An electronic device, such as a Surface Wave, Bulk Wave or pyroelectric device, exploiting the polar nature of an active material in which the active material is lithium tetraborate or a closely related compound for example one which is slightly deficient in Lithium or Boron e.g. (Li.sub.2.-+..delta.1)B.sub.4 O.sub.7 or Li.sub.2 (B.sub.4.-+..delta.2)O.sub.7 where .delta..sub.1 and .delta..sub.2 are small numbers.

Abstract: A Doppler radar system for mounting on a vehicle to sense the speed of movement of the vehicle and to provide an output proportional to the speed of the vehicle. The output is substantially free from errors due to the vibration and of the vehicle. A Janus configuration is also provided which also eliminates errors due to the angle of tilt of the vehicle.

Abstract: Reverse osmosis liquid filtration apparatus, which apparatus comprises an inlet conduit, a reverse osmosis chamber, a pump for pumping liquid to be filtered from the liquid inlet conduit to the reverse osmosis chamber, a reverse osmosis membrane positioned in the reverse osmosis chamber and dividing the reverse osmosis chamber into a first portion for containing concentrated unfiltered liquid and a second portion for containing filtered liquid that has passed through the reverse osmosis membrane, a first outlet conduit which extends from the second portion of the reverse osmosis chamber and which is for the filtered liquid, a reservoir, reservoir separator means, a second outlet conduit for concentrated unfiltered liquid, and valve means.

Abstract: An electrical oscillator for supplying a reactive load circuit, which comprises an automatic tuning arrangement for varying the output frequency of the oscillator in dependence upon changes in the resonant frequency of the load, in which load current frequency or phase sensing means is coupled to the load circuit and provides an electrical signal which is fed in combination with other signals dependent upon the oscillator output frequency to gating means which produces a pulse output of a particular polarity according to whether the oscillator output frequency is too high or too low and in which the output from the gating means is utilized in controlling the oscillator to increase or reduce its output frequency.