Abstract: Voice and data signals can be transmitted simultaneously yet independently over a subscriber telephone line. The speech and data use the same cable pair as far as the local exchange but thereafter they may be routed to the same destination or to different destinations, as desired. Each terminal unit (A or B) has a low pass filter (2) to isolate the voice and data. A data switch (5) switches an oscillator (6) by FSK. Switch (7) locks onto the Data Ready Interface (8). Bandpass filter (9) feeds the signal to the telephone line. A loop back switch LBS provides for testing from the exchange.

Abstract: A device for the controlled release of an active material into an aqueous medium, e.g. body fluids, comprises a water soluble glass container in which the active material is sealed. The container wall has a region of reduced thickness which region dissolves before the remainder of the container wall to release the active material.

Abstract: In an optical fibre submarine cable the ingress of hydrogen ions is reduced if not eliminated by at least one envelope which provides a barrier to hydrogen ions.In one embodiment a copper tape (L) is folded longitudinally around the cable core comprising strength member wires (G,H) split aluminium or coppr tube (E) and optical fibre package (A). The abutting edges (L') are seam welded with less than 0.1% skips. Preferably the folded copper tape is longitudinally welded while a loose fit and subsequently reduced in diameter to leave an accurately determined small annular gap between tubes E and F which is filled with a water blocking material that is highly viscose at ambient temperature and effectively glues the tubes together.

Abstract: Discontinuities, e.g. scratches, in a plastics surface are removed by exposing the surface to a pulsed radio frequency plasma comprising a mixture of argon and hydrogen. After melting has been effected the surface is exposed to an argon plasma to effect cross-linking to form a smooth surface layer.

Abstract: A radio pager for receiving FSK signals has optimally narrow gaussian bandpass filters (F1, F2) and a phase lock loop (11, 12, 13, 14) for preventing local oscillator drift controlled in dependence of the derivation frequency (.+-.4.5 KHz) which is accurately controlled at the transmitter and which is derived from the decoder logic circuit (20).A significant increase in sensitivity is achieved over existing pagers.

Abstract: Certain materials (e.g. polymers, glasses) exhibit the photo-elastic effect, whereby when they are subject to stress become birefringent, which influences a light beam passing through the glass. This beam, e.g. from a laser is collimated and circularly polarized as it approaches the glass and is again polarized as it leaves the glass. This stress is applied, according to this invention, by magnetostrictive strips on the glass which are influenced, by the magnetic field to be measured or the AC bias field. A miniaturized arrangement using this principle is described.

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: 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 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: Infrared optical fibres are provided with hermetic coatings (6) by decomposition or reaction of volatile compounds of the coating material at the surface of the fibre. Materials having melting points greater than the fibre's glass transition temperatures may thus be applied at temperatures lower than the glass transition temperatures. The fibre (1) may be sufficiently hot from a preceding fibre formation (2,3) process in line with the coating process to enable the decomposition or reaction, or additional heating of the fibre by radiation may be necessary in the reaction chamber (7).

Abstract: An accelerometer comprises a quartz beam 1 having on its upper and lower faces surface acoustic wave devices 2, 3 and 2', 3'. The beam is centrally mounted on quartz spacers 4, 5 which have metallized contacts for the lower SAW device. The spacers are carried on a quartz substrate 6 which is supported on a header 7 forming the base of a dual-in-line package. Mass-loading 8 is provided on each end of the beam 1.

Abstract: A method of making a single mode optical fibre directional coupler in which a pair of fibres (30,31) in side-by-side contact is subjected to a succession of drawing operations produced by traversing the fibres longitudinally through a flame (34) while stretching them between a pair of carriages (32,33) driven at slightly different speeds.

Abstract: A Hall effect device for responding to weak magnetic fields uses a small chip of gallium arsenide located between the overlapped ends of two flux concentrators. The spacing between the concentrators may be as small as 95 micrometers. The flux concentrator, which serve to enhance the device's sensitivity are made of amorphous magnetic material, i.e. a metallic glass, which has high permeability.

Abstract: An energy efficient output circuit for a static random access memory includes a pair of output transistors each driven by a bootstrapped driver stage. This requires less current than conventional amplifier chain.

Abstract: A digital switching arrangement for use in a telecommunications exchange handling channels of digital information in time division multiplex form. The digital switching arrangement being particularly suited for use in stored program processor controller environments. The arrangement comprises a digital switching network and a control equipment. The control equipment includes an input queue and an output queue each arranged to store processor input and output messages respectively. The control arrangement is arranged to asynchronously process each output message to process switching network path connections and to generate in the input queue an input message indicative of the actions performed. Each output message includes switching network identification information indicative only of the identities of the incoming and outgoing exchange highways and channels to be involved in the switching network path to be processed.

Abstract: A digital switching telecommunications exchange handling pulse code modulated information samples in time division multiplex form on incoming and outgoing junctions. The exchange includes a receive interface for each incoming junction and a transmit interface for each outgoing junction and a pair of identical time division multiplex switching networks providing interconnection paths between any incoming junction channel and any outgoing junction channel. Under non-fault conditions exchange calls use indentical paths in each network and the transmit interfaces include error checking and comparison arrangements for each pair of information samples received under fault conditions the transmit interfaces can be arranged to select the non-faulty sample on a per channel basis or can be biased to select one network exclusively.

Abstract: Reduction of noise in a television signal is achieved by comparing signals from successive frame or field scans and noting the differences. Low amplitude differences are assumed to represent noise and are attenuated. Differences above a predetermined level are assumed to represent movement and are not so attenuated by a factor K. Where there are inherent differences between the signals compared, for example they are different fields of an interlaced scan or are color signals with different subcarrier phases, the signal from the earlier scan is modified to compensate for these differences and provide a signal for comparison which is a better estimate of the expected signal on the later scan.

Abstract: Sequential/interlace scan conversion of NTSC or PAL color television signals is effected by an encoder the output of which is connected to the input of scan conversion apparatus. Controllable phase shift means is included in either the color signal input or the subcarrier input of the encoder and is adapted to vary the phase of the modulated subcarrier for each line of the received color signal by an essentially integral number of quarter cycles in dependence upon the line number. The control is such that the conversion apparatus provides an encoded output signal with the color subcarrier in PAL or NTSC format. The invention can also be used in converting between different types of interlace systems.