Abstract: A method and assembly of providing a building or other location with an optical fibre ribbon cable having a plurality of optical fibres terminated by a connector is provided. The method and assembly enable optical fibre ribbon cables to be terminated in a factory rather than on site, and then to be installed by blown fibre methods, even when the ribbon cable is terminated by connectors that are too large to be inserted in the duct. The assembly includes an optical fibre ribbon cable having a plurality of optical fibres, a unitary insert for a connector that terminates at least one end of the cable, and a housing for the connector which can be located about the insert to form a composite connector. The optical fibre ribbon cable as thus terminated is capable of being propelled along a duct by fluid drag of a gaseous medium.

Abstract: A method for installing a lightweight optical fiber unit, preferably less than approximately 10 g/m, into a tube, by pulling the optical fiber unit through the tube using a pulling member. The pulling member may be attached to the optical fiber unit by a braided sheath. Alternatively, the pulling member itself may be a braided tube.

Abstract: An optical network in which data signals are encoded with a wavelength corresponding to the address of the signals includes at least one point therein, a data routing switch (1) which comprises: a wavelength comparator (3) for example a Brag grating or a notch filter that will receive data signals and has associated therewith a characteristic wavelength so that it will send the data signal along a gate enabling line (5) or not in accordance with the relationship between the data signals encoding wavelength and the characteristic wavelength of the comparator, and a gate (7) which transmits or blocks the data signal in response to the presence or absence of the data signal in the gate enabling line and a number of data routing switches having different characteristic wavelengths so that routing of the data is determined by which switch characteristic wavelength matches the data encoding wavelength.

Abstract: An optical line system comprises: (1) an optical fiber that includes a plurality of reflectors, for example Bragg gratings, located at different positions along the optical fiber; and (2) a monitoring arrangement located in the region of one end of the optical fiber for monitoring the system by an optical reflectometry method in which light is reflected by the reflectors. The system is characterized in that at least two of the reflectors have reflectivities that differ from one another, the reflector that is more distant from the monitoring arrangement having a higher reflectivity than the Bragg grating that is nearer to the monitoring arrangement. Preferably the reflectivities of the reflectors increases as the distance from the monitoring arrangement increase, the reflectivities preferably having the relationship (1) R.sub.n-1 -(2T.sup.2 R.sub.n+1)-(1+4T.sub.2 R.sub.n)1/2/2T.sup.2 R.sub.n where: R.sub.n is the reflectivity of the n th relector from the monitoring arrangement, R.sub.

Abstract: Laser marking compositions, articles of manufacture using same and methods of preparing said articles and compositions are disclosed which comprise a polymer including a cyclopentanone compound which is thermally stable at temperatures required to melt process polymers, but which will eliminate water when subjected to an excimer laser to form a visible mark comprising a cyclopentadienone.

Abstract: A polyaniline is characterized by a nuclear magnetic resonance spectrum in its leuco form showing only two .sup.13 C peaks, indicating the substantal absence of chain branching, and preferably by a molecular weight (M.sub.p) above 90,000 and up to about 170,000 (more especially 100-140,000). Oriented films of such polyanilines in the protonated emeraldine oxidation state have electrical conductivities up to at least around 500 S/cm.They may be made by oxidizing aniline in aqueous solution with a persulfate under the combination of conditionsthat the acidity of the solution throughout the reaction is such that if its temperature is adjusted to 20.degree. C. it will have a pH in the range from about -0.2 to +3.0;that the temperature of the solution is in the range from -5.degree. to about -40.degree. C.

Abstract: This invention provides a device for capacitively measuring the distance to an object, which comprises an electrode that will couple capacitively with the object, a shield that surrounds the electrode and is electrically isolated from the electrode by means of insulation, and a layer of insulation that surrounds the shield, wherein the insulation between the electrode and the shield, and the insulation that surrounds the shield, are formed by deposition.This invention further provides a method for measuring the distance to a solid object, which comprises forming an electrode that will capacitively couple with the object, depositing a layer of insulation over at least part of the electrode so that the insulation surrounds the electrode, depositing a layer of metal over the insulation to form a shield, and depositing a second layer of insulation over the shield.

Abstract: Electric cables with sector-shaped conductors, for maximizing duct capacity, are made by a process in which the shaped metallic conductor is first preformed into a helical twisted form ("pre-spiralled"), next covered with insulation of EPR, polyethylene or other suitable insulation material to form a core, third subjected to ionizing radiation to crosslink the insulation, and fourth laid up with other like cores to form a cable. All the steps are well known yet the potential to apply radiation crosslinking to this type of cable--in which other crosslinking techniques are wholly impracticable--has not hitherto been appreciated.

Abstract: An optical cable for use in an overhead optical transmission system in which the cable is supported along the route of the system by means of towers, masts or other upstanding supports that are also employed to support electrical power cables, includes one or more optical fibers and an electrically insulating jacket (8). The cable includes an array of elongate conductive elements (10, 12) each of which extends along a portion of the cable, adjacent conductive elements axially overlapping each other with overlapping portions circumferentially spaced apart to form a composite conductive path that extends along the cable and is interrupted when the cable is dry. Adjacent conductive elements (10, 12) are resistively coupled to each other when the surface of the cable is wet to form a continuous electrically conductive path along the cable. Such a form of cable has the advantage that the dry-band arcing under wet conditions is reduced by disrupting the geometry that allows such bands to form.

Abstract: A tool for stripping semiconducting insulation shield from an end part of a high-voltage cable in preparation for jointing or termination and at the same time circularising it has an annular body carrying a stripping blade and means (such as a handle or a motor drive) for rotating the body around a cable end extending through it to strip a surface layer from the cable end in a generally helical manner. So that the movement of the blade follows the general cylindrical shape of the cable end and is not significantly influenced by minor local departures from nominal dimensions, the annular body is mounted on the cable end by means of a plurality of resilient rings, for example located by grooves in its inner surface or in the inner surface of a second, non-rotating, annular body coupled to it. The tool can also be used to strip insulation and optionally also conductor shield from another end portion of the cable.

Abstract: A linear element (1,61) suitable for extending between, and being supported by, towers of an overhead electrical power transmission system, includes one or more electrically semiconductive components (54, 62) that cause the element to have a linear resistance of 0.05 to 100 Mohms m.sup.-, and which exhibit a negative temperature coefficient of resistance. The element may be a rope used for stringing up conductors of the system or it may be an optical cable. Preferred materials for forming the semiconductive components include carbonaceous fibre tows formed from pyrolised acrylonitrile fibres. The element has a controllable and reproducible resistance for reducing or eliminating dry-band arcing.

Abstract: An overhead electrical power and optical transmission system, comprising overhead electrical phase conductors (2) extending between and supported by towers (10), and at least one optical cable (1) that extends between and is supported by, the towers. Each optical cable has a resistive element (12) that is removably supported thereby and which extends from a tower (10) where it is earthed part of the way along the span of the optical cable, and the resistive element has the necessary length and conductivity such that if a dry band (6) occurs on the cable at the end of the element, the potential difference (VG') across the band is insufficient to form an arc, such that any induced current is insufficient to sustain any arc that may occur across the dry band.

Abstract: A device for testing an electrical line by time domain reflectometry, using a pulse generator to generate a series of test pulses, a programmable delay generator which provides a delay in the transmission of the test pulses, and an analog to digital converter which samples the reflected signals from the line and sends them to memory. The test pulse is transmitted to the line and a number of digital sample values are produced sequentially at a defined sampling rate by the delay generator, which is incremented or decremented to advance or retard the transmission of the test pulse by 1/n times the sampling period, and sample values from each pulse obtained. The above steps are repeated until transmission of the test pulse has been retarded or advanced by at least (n-1)/n times the sampling period and sample values from each pulse obtained, with the sampled values arranged in order of increasing time difference between transmission of the test pulse and sampling.

Abstract: A superconducting ceramic composition which is free of thallium, the composition having a unit cell containing two perovskite structure copper-oxygen planes and a rocksalt structure layer having a single plane containing cadmium.

Abstract: A cable comprising a core enclosed in an external sheath of a char-forming low-smoke-and-fume composition is characterized by a tape of flexible mineral material, preferably a woven glass-fiber tape, wrapped round the core and by an adhesive bonding the tape to the sheath. Hot-melt adhesives based on ethylene/vinyl acetate copolymers with tackifier resins are suitable. By bonding the sheath to the underlying tape, retention of the charred remains of the sheath under fire conditions is considerably improved with consequent improvements in flame retardance, smoke levels and fire survival.

Abstract: A circuit board injector/ejector device for use with a circuit board to be accommodated in a rack housed in an enclosure comprises a body adapted to be secured to a front plate secured to the circuit board and a lever pivotally mounted on the body. The device is adapted to assist in providing the force necessary to effect a multiplicity of pin and socket connections at the rear of the circuit board when the circuit board is introduced into a rack and to assist in providing the force necessary to effect disconnection of the multiplicity of pin and socket connections at the rear of the circuit board when the circuit board is withdrawn from the rack.

Abstract: In effecting an end-to-end fusion splice between two optical fibres, the optical fibres are introduced into opposite ends of two support members so that parts of the optical fibres protrude from the members. The fibres are secured in the members and the protruding parts are cut to form tails of predetermined lengths. The support members are then arranged in axial alignment and one is caused to move axially towards the other until the end faces of the protruding tails are spaced a predetermined distance apart. Fusion splicing is then effected, the support members are permanently secured together and mechanical protection for the fusion splice is provided.

Abstract: An optical connection between optical fibres of two optical cables includes a cassette in which is mounted a preformed component having a housing and discrete optical conductors which are so disposed in the housing that opposite end parts of each of the conductors, each of which end parts is formed of a length of optical fibre, protrude from the housing at an acute angle to one another lying in the range 0.degree. to 90.degree. and that at least a part of an optical signal entering any one of the discrete optical conductors along one of its protruding lengths of optical fibre will pass along a discrete optical path and the part of the optical signal will leave the optical conductor along another of its protruding lengths of optical fibre.

Abstract: Apparatus for use in terminating an optical fibre F in the bore of a tubular connector body C comprises a movable support 1 having first gripping means 5 for holding a tubular connector body in a fixed position on the support, second gripping means 7 for holding an optical fibre in a predetermined position in which the fibre extends through and protrudes from the bore of the connector body when so held, and a handle of thermally insulating material. A first mounting 10 for temporarily supporting the movable support 1 is of such a form that it facilitates ready positioning of the connector body C and optical fibre F. A second mounting 20, to which the movable support 1 is transferred from the first mounting 10, incorporates heating means for hardening of heat-hardenable adhesive employed to secure the optical fibre in the connector body. Reduction in the level of manual dexterity needed to ensure consistent satisfactory terminations can be achieved.

Abstract: In a "Futurebus+" backplane, at each end of the backplane the signal lines are each electrically connected to a power bus spaced from the rear face of the backplane via a discrete resistor which is housed in a throughbore in a body of electrically insulating material detachably secured to the rear face of the bakplane and which is electrically connected between the power bus and a pin soldered in a plated through hole and interconnected in the signal line. The ground lines are each connected to the power bus via a discrete capacitor which is housed in a throughbore in the body and which is electrically connected between the power bus and a pin soldered in a plated through hole and interconnected in the ground line. In the event that a resistor or capacitor should be faulty, only the signal or ground line to which the faulty resistor or capacitor is connected will be out of service until the faulty resistor or capacitor is replaced.