Abstract: An indexing mechanism for the volume control of a telephone bell comprises a slot and associated indexing notches which co-operate with a guide pin and an indexing pin respectively. Volume control is effected by forcing the indexing pin over one or more notches as desired. The volume setting is not easily altered by vibration of the instrument.

Abstract: A cable entry gland which will provide an effective seal at the end of a pressurized fibre optic cable so that the pressurization within the cable is not lost when the cable is removed from a repeater box consists of a housing sealed to the outer covering of the cable. The optical fibres extend through the housing and out through the end wall of the housing, suitable seals being provided between the optical fibres and the wall. A strain wire connects the cable to the end wall to prevent stresses passing to the fibres. It is possible to replace a broken fibre without dismantling the gland by drilling out the seal in the end wall, withdrawing the broken fibre, threading a new fibre through the gland and re-sealing the fibre to the wall.

Abstract: In an optical fibre switch it is important that the ends of the fibres are very accurately aligned after the switching operation so that the minimum amount of light is lost in the switch. This is achieved by mounting an optical fibre in each of the corners of, for example an accurately formed square hole, and having a moveable fibre which can be moved into each corner and which is accurately aligned with one of the other fibres by the sides of the corner itself. Optical switches are used for transmitting light from a light source to one of several different locations. Typical uses are the transmission of data, telecommunications and similar signal transmission systems.

Abstract: This application describes a receiver in which channel selection is controlled by a frequency synthesizer a sweep of available channels is made by a channel selecting arrangement and this sweep is arranged to be stopped when a signal is received. When the sweeping is stopped a fine tuning arrangement takes control to respond to the frequency of the received signal and to compensate for any drift of that signal.

Abstract: A method of assembling an electrolytic capacitor comprise the following steps: an annular sleeve shaped cathode is inserted into the open end of a can; an anode structure is inserted into said can in a spaced apart relationship from said cathode, the space between said anode and cathode being filled with an electrolyte, said anode structure having an aperture or recess for reception of an anode lead; a primary seal, for sealing the open end of the can, and comprising an anode lead electrically isolated from the rest of the seal; is formed; a secondary seal is positioned on the anode lead on the inside face of said primary seal to form a seal between said anode lead and said can prior to sealing of the primary seal of said capacitor; the end of the anode lead projecting from said secondary seal is machined to provide projections on said lead; the capacitor is assembled by forcing the projecting portion of said anode lead into said anode until the primary seal is in position; the primary seal is welded around i

Abstract: An intruder detector consists of an element of pyroelectric material having three defined regions; two being active to infra-red radiation and one being relatively inactive to infra-red radiation. The inactive region and one of the active regions are connected together in parallel and the other active region is connected in series with these two. The arrangement has full cancellation of environment effects while being partially unbalanced for infra-red detection so that isolated areas of infra-red radiation (such as an intruder) can be detected at long and short ranges.The element is used with a concave mirror for increased zonal coverage.Each of the regions of pyroelectric material has a substantially constant thickness and all of the three regions have the same thickness.

Abstract: A display device comprises a light emitting diode chip mounted on a substrate. To reduce or eliminate reflections from metallic connections to the chip, the metallic parts are electroplated with a light absorbing material.

Abstract: A light transmission guide comprising an anodic film of light transmitting material having a first anodised portion with a relatively high refractive index and at least a second portion with a relatively low refractive index, in which anodic film the increase in refractive index from said relatively high to said relatively low value is smooth and continuous in the vicinity of an interface between the first and second anodised portions, and in which the outer surface of said anodic film possesses a minimum amount of structural discontinuity on an atomic scale.

Abstract: The end of a glass fibre of the graded or at least stepped, index type, or in the case of a clad fibre, the end of its core, is etched with an etchant which varies in etching power according to the composition, and thus in a graded or stepped - index fibre according to the index, of the fibre - core material, thereby producing at the end of the fibre a recess or "well" whose depth increases from the edge towards the axis of the fibre.

Abstract: An indicating device is provided, especially in the form of a taximeter which comprises counter means which is clocked by time pulses applied to it and which is reset by distance pulses applied to it and when it reaches a predetermined count, the counter means being arranged to afford an output each time it is reset and means being provided operable on the distance pulse immediately following the counter means having assumed said predetermined count for producing an output in dependence upon the residual count of said counter means on the application thereto of the said distance pulse for affording a correction pulse that is effectively subtracted from the output afforded by the counter means to afford a corrected pulse train that is used to compute a fare to be charged.

Abstract: This invention relates to an optical system for the production of a beam of light having a uniform intensity distribution. The optical system includes at least one Fresnel biprism for converting a beam of light having a non-uniform intensity distribution into a beam of light having a uniform intensity distribution.

Abstract: A hand-operated portable electric ignition device for the ignition of gas comprises within an insulating housing means for producing from a battery relatively high voltage alternating current pulses in response to the operation of a manually-operable switch, said means including a transistor oscillator circuit, rectifying means for rectifying the alternating current pulses for charging a capacitor and means arranged to conduct to provide for the discharge of the capacitor through the primary of a transformer in the output circuit of which is a spark gap across which sparking occurs when the charge voltage on the capacitor reaches a predetermined value.

Abstract: An indicating device especially in the form of a taximeter comprises a first register for accommodating and storing information relating to distance related pulses received by the device, a second register for storing information relating to the number of distance related pulses that correspond to a predetermined threshold speed that would be received in a predetermined time period, and a third register for storing information relating to an accumulating total, means being provided for comparing the information stored in the first and second registers, preferably at successive time intervals corresponding to the predetermined time period, and for adding the information of one or the other thereof to the information of the third register dependent upon their relative values.

Abstract: A pyroelectric detector which includes at least one pyroelectric element consisting of a pyroelectric material sandwiched between first and second electrodes, and a semiconductor chip having a field effect transistor formed on one surface thereof and having an electrical contact for the gate electrode of the transistor formed on the surface thereof, opposite to said one surface, the gate electrode contact of the chip being secured in electrical contact to the first one of the electrodes of the pyroelectric element, the size of the chip being such that a major portion of the first electrode is not covered by the chip.

Abstract: An optical apparatus for use in association with an optical fibre having a core member and a cladding member which surrounds the core member and which has a refractive index less than the refractive index of the core member, the apparatus including optical means adapted to examine light radiated at an angle through the cladding member and thereby determine the characteristics of the optical fibre and/or facilitate the application of an illuminating beam of light at an angle through the cladding member and to thereby excite a single mode in the optical fibre; and means for maintaining the angle between the light and the fibre axis substantially constant.

Abstract: An electrically conductive composite material which consists of a mixture of silver, not more than 50 weight percent of cadmium oxide and not greater than 2,000 parts per million of compounds of potassium.

Abstract: An information store comprising (a) a known latching circuit which comprises cross connected metal-oxide-silicon transistors and metal-nitride-oxide-silicon transistors and which is accommodated on an integrated circuit chip to which only earth and negative power is supplied, and (b) control means, positive potential for erasing being developed by applying earth and negative potentials selectively to input terminals of the control means, the control means comprising a resistor in series with a capacitor, and an output terminal at the junction of the resistor and capacitor.

Abstract: The present invention describes the manufacture of a chip having a stratum in which a number of diffusions are spaced from each other by boundaries whose widths is the width of a gap. The diffusion on one side of a boundary is formed by ion bombardment, and that on the other side by heat transfer of ions of a material with which the film has been doped.

Abstract: An electrical integrated circuit package protector capable of protecting an integrated circuit chip, which accommodates a metal-oxide-silicon transistor, and which is enclosed in a package to be protected by the protector, from damage by static electricity appearing at soldering tags which are connected to the chip; which protector comprises a girdle capable of encompassing the package to be protected, and when the package is encompassed by the girdle, both of making detachable physical engagement with the package, and of establishing electrical connection between the soldering tags of the package.

Abstract: A fibre optic pressure sensor which includes at least two lengths of optical fibre each one of which is secured to a surface of a separate one of a number of spaced-apart member, at least one of which is resilient, the optical fibres being situated in the space between the said members and adapted to be brought into alignment when at least one of the said members is deflected by the application of external pressure to the sensor.