Abstract: An optical fibre is provided with a moisture barrier layer by exposing a plastics coating on the fibre to a pulsed plasma in order to modify the surface, for instance by implantation of silicon and/or by the deposition on the plastics layer an inorganic layer such as a non-stoichiometric composition of silicon and carbon or silicon and nitrogen.

Abstract: A telephone exchange conference circuit for three-party conferences, receives the PCM bytes from the conferees in a FIFO store (4), and checks the bytes in a processor (1) to find the one for the loudest outgoing speech. This is then sent to another FIFO store (5) for transmission to the other conferees. This loudest speech sample is sent to all conferees other than the one which originated that sample: he gets a silent code.The system has two time slots per conferee, one for "talk" and for "listen".

Abstract: Polysilicon elements of integrated circuits, for example gates (24) or interconnects, are provided with metallic silicide layers (26) in order to take advantage of the lower resistivity thereof. The polysilicon elements are defined on an oxide layer (23) disposed on a silicon substrate (20) before polysilicon metallization. After polysilicon metallization the metal and polysilicon are caused to interdiffuse to form silicide layers (26) covering the polysilicon elements (24).

Abstract: A temperature compensated crystal oscillator in which the base emitter voltage of transistors in an integrated circuit is used to provide substantially linearly temperature sensitive outputs which are employed to generate a series of polynomial functions of Chebyshev-like form which are summed and used to control a varicap diode in the oscillator feedback path.

Abstract: An optical fibre pulling tower is made of tubular modular substructures (5) of synthetic granite mounted one on top of the other by means of joining plates (6) cast in situ. A baseplate (13) sits on a concrete raft (14) and is adjustable to be exactly upright.

Abstract: A cabling machine for making single optical fibre cable with two layers of stranded armid yarn enclosed in a yarn outer wrap which employs a vertical axis for cabling and uses peripheral pay-off of the aramid yarn (34,39) from bobbins 33 mounted on a pair of separately driven turntables (21,22) and peripheral pay-off of the yarn wrap (45) from a spool (44).

Abstract: All the layers of the anode foil of an electrolytic capacitor roll (5) are cold welded to a piece of tabbing (8) using radiussed weld tooling (10, 12, 13) which bends the foil layers in the course of the welding operation so as to enable a good weld to be effected. The cathode foil layers are welded to their piece of tabbing in the same way. Optionally the roll may be partially flattened at the time the welds are made.

Abstract: In a digital PCM-TDM telephone exchange, supervisory tones needed are centrally generated by a digital synthesizer. This includes a PROM (1) in which PCM codes for the tones needed are stored in successive memory locations. The tones used are the DR tone, which is a mixture of 350 Hz and 440 Hz, and the BN tone, which is 400 Hz. These are read out under clock pulse control (5-6-7) such that the DR tone bytes are read out at time slot 0 and the BN tone bytes are read out at time slot 1. They are then sent over a common intelligence bus (4) to all line and trunk interfaces.At each such interface the tone bytes are converted to analogue form so as to be continuously available. The tone (or tones) to be used is (or are) selected in response to instructions from the central control each of which specifies a program in the interface's processor. Such a program controls both the selection of the tone (or tones) needed, and the cadence (continuous, or interrupted in a defined manner).

Abstract: A ceramic chip capacitor comprises electrically conductive layers extending alternately to two opposing edges of a rectangular ceramic body. The other two edges are provided with electrical terminations. The edges to which the conductive layers extend are partially covered with fusible metallic films which connect the layers to respective terminations. The fusible films isolate the capacitor from associated circuitry if the capacitor fails and effects an internal short circuit.

Abstract: A dielectric composition, particularly suitable for the manufacture of ceramic capacitors, comprising lead magnesium niobate and lead zinc niobate. These may be additives, such as one or more oxide additives chosen from the group comprising silica, manganese dioxide, zinc oxide, nickel oxide, alumina, ceric oxide, lanthanum oxide and tungsten oxide, gallium oxide, titanium dioxide and lead oxide, or additives such as bismuth stannate. The compositions can be fired at temperatures between 980.degree. and 1075.degree. C. so that in the case of multilayer ceramic capacitors high silver content internal electrodes can be used. Higher dielectric constants, for example 9000 to 16,300, of the fired ceramics than conventional ceramics are obtained, thus permitting capacitor device size reduction.

Abstract: The primary coating (2) of an optical fibre element is reinstated over a fused joint between two silica fibre elements (3) by a casting process. The jointed silica fibre elements are arranged in a groove (8) of a mould (9, 10, 11) and liquid uncured primary coating material placed into the groove, the groove ends being blocked by the existing primary coatings (2) on the fibre elements (3). The coating material in the groove is cured by, for example, heating the mould. Secondary coating material (1) may be injection moulded using a two-part mould to reinstate the secondary coating over the cast primary coating.

Abstract: A dielectric composition, for use in the manufacture of ceramic capacitors, and comprised of barium titanate (BaTiO.sub.3) with small additions of niobium pentoxide (Nb.sub.2 O.sub.5) and gadolinium sesquioxide (Gd.sub.2 O.sub.3).

Abstract: A dielectric composition, particular suitable for the manufacture of ceramic capacitors, comprising non-stoichiometric lead magnesium niobate, non-stoichiometric lead iron niobate and one or more oxide additives, which may be chosen from the group comprising silica, managanese dioxide, ceric oxide, lanthanum oxide, zinc oxide, alumina, tungsten oxide, nickel oxide, cobalt oxide and cuprous oxide. The compositions can be fired at temperatures between 980.degree. and 1075.degree. C., so that in the case of multilayer ceramic capacitors high silver content internal electrodes can be used and, in cases where three or more of the oxide additives are employed, higher dielectric constants, for example 10600 to 16800, of the fired ceramics than conventional ceramics can be achieved, thus permitting capacitor device size reduction. Additions of lead titanate may also be made to the dielectric compositions.

Abstract: An animal feed additive comprises a composite of a relatively insoluble binder, a particulate soluble material and an active material. The particulate material is such that it is readily soluble under a particular range of pH conditions, e.g. under said conditions. Dissolution of the particulate material renders the binder water permeable thus permitting release of the active material.

Abstract: In a telephone line feeding arrangement, the line current is monitored by a multi-resistor network (R.sub.p R.sub.s) and the output of the network applied to the inputs of an operational amplifier (A3). The output of this amplifier, which is a voltage whose value depends on the line current, is compared by a comparator (A4) with a reference voltage (V.sub.R) to produce a control voltage for a variable voltage (VVS), the output of which provides line feeding voltage.In an alternative, the monitoring is effected by connecting the two line wires each via a resistor to one of the inputs of an operational amplifier (A6) whose output is a voltage dependent on line voltage. This voltage is applied to an input of another operational amplifier (A7) where it is in effect added to a reference voltage (V.sub.R). The output of this amplifier (A7) is used to control the variable voltage source (VVS), which in turn controls a constant current source (CCS) whose output provides line current.

Abstract: In a fully digital telephone switching system, a digital switch may serve a number of PCM sub systems each having separate forward and reverse highways and each serving a number of subscribers' lines. The highways are grouped in blocks of eight, from which intelligence is received in serial byte-interleaved form and converted by serial-parallel converters to parallel byte-interleaved form. While in this form they are switched to other channels and applied to a super-multiplexer which they leave in parallel byte-interleaved form from which they are restored by another converter to serial byte-interleaved form for application to the switch's outputs. For the reverse channel the arrangement is the reverse of the above, i.e. serial-parallel conversion, switching and parallel-serial conversion to the line multiplex highways. For local calls a loop-back connection is provided via a fixed delay of half a frame time. Thus, if the outputs fail, the arrangement can still handle local calls.

Abstract: The direct current line feed for a telephone subscriber's line is derived from a variable voltage source connected to the line. In one case, the source is series connected in one leg of the line while in the other case it is connected across the line. In the first case there is a constant current source across the line while in the second case the voltage source is a constant current device. In both cases a pair of matching resistors is connected across the line with the center tap grounded to provide a high resistance balanced termination for the line. In both cases a high impedance monitor is connected across the line to monitor the voltage conditions on the line, and this, via a control circuit controls the voltage source and the separate constant current device if provided. This enables line voltage to be adjusted to take account of line length without introducing undesirably large dissipation.

Abstract: To limit the line current dissipation in a telephone system it is considered desirable, especially in electronic systems, for the line current feed to be constant current. In the present arrangement the constant current supplied to the line is made adjustable in accordance with line conditions, especially the voltage between the line wires. A high impedance monitor is connected across the line to monitor the voltage between the two wires and to produce therefrom a reference voltage which is applied to the constant current generator so as to cause it to generate a current for line feed whose value is determined by the line voltage.

Abstract: A telephone subscriber's line interface for a system in which the telephone instrument and the connections therefrom to the exchange use analogue, while the exchange is digital is described, in which electro-mechanical components are eliminated.To achieve this a microprocessor serves a group of lines on a multiplexed basis, responding to conditions of the line as determined via a high impedance monitor and analogue-to-digital conversion means. It also responds to control inputs from the rest of the exchange. In response to the above inputs it controls line feed, signalling, etc. via digital-to-analogue conversion means and a line driver.

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.