Abstract: An adjustable ratio divider comprises a controllable gate connected in series with a divider for passing a clock signal in pulse form whose frequency is to be divided. A means is provided for controlling the gate to subtract a selectable number (including zero) of clock pulses from the clock signal to control the division ratio of the divider.

Abstract: A method of producing a transducer in which the fine tolerances are obtained by a two stage moulding process. Features include retention of the coil by the moulding process and accurate dimensioning of the magnet by depression of the soft iron core.

Abstract: A diamond heatsink for semiconductor devices comprises a stud into which the diamond is pressed. The stud is held by friction in the end of a hollow split cylindrical holder. The holder is clamped in a base or wall member by a locknut which is screwed into the base or wall member and urges two half-conical collets into contact with the holder. The holder is also mounted by a screw thread in the locknut to allow the position of the semiconductor device to be adjusted.

Abstract: A sonar survey apparatus comprises a submersible vessel having a structure adapted to receive a towing cable. A sonar signal transmitter is mounted on the structure. At least one acoustic reflector is mounted on the structure and is shaped to produce, in a focussing plane, line foci of acoustic echo signals received from remote positions. A line array of receiver transducers are mounted on the structure in the focussing plane and extend in a line substantially at right angles to the line foci. Each receiver transducer element has an output for providing a signal representative of a focussed echo signal. A selector is coupled with the output of each of the receiver transducer elements and has a control input and an output. The selector is operable in response to the control signal to select the output of a receiver transducer element, relating to a predetermined direction, for display.

Abstract: A coupler for an optical fibre system includes a retroreflector which because of its properties allows considerable relaxation in the positioning of the fibre in relation to the retroreflector. The principle may be used to provide switches or couplers.

Abstract: A control system for a time division multiplex digital switching exchange has a number of telephony groups located on separate shelves which are interconnected by an intershelf bus. The intershelf bus comprises two address buses and a data bus. A common control computer inserts addressing data into two registers in a digital switch controller (DSC) which uses that data to control the transfer of data between telephony groups by way of the intershelf bus. The DSC also includes transmit and receive registers connected to the data bus which allows the transfer of data to and from the shelves and the common control computer. Should the common control computer require to read data from the DSC it addresses the DSC as one of the shelves (i.e., inserts the address of the DSC in the two registers of the DSC) to cause the DSC to transfer or read data to or from the transmit and receive register.

Abstract: An electronic switching system in which digital data is required to be exchanged between two pieces of electronic apparatus such as two telephone subscribers, in which a parallel time division multiplex highway is used to carry the data, the highway being divided into two paths, the data being transferred in both directions during a single time period using the different paths for each direction, identification of the transmitting and receiving parties being by use of two address buses in a single time slot period.

Abstract: Mechanized mail sorting offices require packets to be sorted according to destination into one of many bags. A typical mechanized system includes a loading mechanism for transferring packets from stationary input pockets onto a continuously moving sequence of containers which pass all destinations in turn and unload as required. The system according to the invention consists of a number of separate self powered single trolleys (TL) which run on a tracking network. Each trolley (TL) is adapted to be programmed with the route to be taken to the destination of the packet(s) loaded into it. The trolley (TL) co-operates with en-route track-side signposts (TSB) enabling steering arrangements (SM) in the form of a guide arm at the front of the trolley (TL) to guide the trolley around the tracking network to and from its required destination for unloading its package into a bag.

Abstract: Optical apparatus for determining for example by display on an oscilloscope the refractive index profile across an optical fibre including an ellipsoidal reflector and a scanning system for a laser beam directed towards one focus of the ellipsoidal reflector at which point the fibre to be examined is placed and including a detector which is relatively small in size situated at the other focus of the ellipsoidal reflector.

Abstract: A supporting assembly includes a base member having a spherical depression and a supporting platform having a hemispherical projection. The projection is mounted in the depression and a pillar projects through the two members, the pillar being rotatable in the base member and extending through a slot in the hemispherical projection. The top of the pillar is square in section and co-operates with a channel of similar width formed in the hemispherical projection having the same axis as the slot. The arrangement permits a VDU to pivot in one plane only relative to the pillar (so that the edge of the screen remains parallel to a desk top) and to swivel on the base member.

Abstract: In a semi-conductor laser of buried active laser layer type, the laser layer is located between a layer of n-type material and a layer of p-type material, the sides of the active laser layer and at least a portion of the n-type layer and the p-type layer being covered with a plurality of thin layers with a doping sequence such that a large number of p-n junctions are included in the plurality of thin layers.

Abstract: A keyboard (61) is provided with rubber (silicone) buttons (64, 66) with collapsible webs (14) connecting the buttons to a base layer (10, 40, 60). A solid finger of rubber (20) underneath each button actuates a membrane switch (23) underneath the button. Additionally or alternatively a conductive member (52) can be attached to the end of the finger (20) to make two contacts (48, 50, 56, 58). The buttons and the finger can be of any suitable section, such as round, rectangular etc., and a variety of types of membrane switches can be used.

Abstract: A method of forming a layered structure, which method comprises depositing a first metal layer on a substrate, depositing a barrier layer on the first metal layer, depositing a second metal layer on the barrier layer, forming a first masking pattern on the second metal layer, etching the first and second metal layers and the barrier layer in accordance with the first masking pattern, removing the first masking pattern, forming a second masking pattern on the second metal layer, etching the second metal layer in accordance with the second masking pattern, removing the second masking pattern, depositing a dielectric layer having a thickness sufficient to cover the second metal layer, etching the dielectric layer to expose the second metal layer, and depositing on the etched dielectric layer and exposed second metal layer a further metal layer to contact the exposed second metal layer.

Abstract: An integrated circuit processing method comprises the formation on a substrate of a metallized conductor pattern. A layer of insulating material is formed over the conductor pattern and a mask is superimposed thereon. The mask is resistant to plasma etching and is provided at predetermined positions with apertures defining required void outlines. Plasma etching through the mask forms vias in the insulating layer which communicate with the metallized conductor pattern. The mask is removed to leave the integrated circuit with communicating vias which enable connection to the conductor pattern.

Abstract: A radar, lidar, or sonar system, comprising a transmitter and a receiver, the receiver including means for forming a plurality of contiguous receiver beams so as to define a predetermined angular sector of cover and means for narrowing each of the beams while contiguity is maintained between them, whereby the angular sector of cover is reduced for longer ranges.

Abstract: Stabilized underwater apparatus (34) which is for being towed or tethered and which comprises a cylindrical body portion (40) provided with at least two stabilizers (74), the stabilizers being elongate such that they extend over a major portion of the length of the apparatus, the stabilizers being of a plate-like construction, the stabilizers extending in a plane substantially parallel to the adjacent surface of the cylindrical body portion, and the stabilizers being spaced apart from the adjacent surface of the cylindrical body portion.

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 .-+., S.sub.1 B.sub.4 O.sub.7 or Li.sub.2 B.sub.4 .-+.S.sub.2 O.sub.7 where S.sub.1 and S.sub.2 are small numbers.