Abstract: In an arrangement for decoding code labels embedded in audio signals by inserting signal bursts at selected frequencies into notch frequencies in the audio signal, problems of speed variations in the device producing the audio signal creating notch frequency variation are overcome by providing a plurality of decoders in parallel receiving an incoming signal, each decoder having notch frequencies incrementally displaced from those of the other decoders.

Abstract: A method for inserting coded information into an image comprising the steps of analyzing the image, identifying the edge regions within the image, determining the strength of the edge region, and producing an edge function which is dependent on the strength of the edge. The edge function is added to the image in order to represent coded information.

Abstract: Apparatus for coupling power into a body of gas by induction to provide a gas discharge, comprises a source of a/c power (3) coupled to a circuit arrangement having an inductor comprising two coils (1, 2), each constituted by a respective elongate conductor, the conductors each having one end coupled to the circuit arrangement at opposite respective sides of the inductor, and having the other end at a floating potential. The mutual capacitance between the coils, together with the inductance of the inductor as a whole, constitute a balanced self-resonant circuit having a resonant frequency which is greater than 1 MHz and less than 100 MHz. This arrangement can reduce temperature variations in the resonant frequency and can reduce unwanted r.f. emissions.

Abstract: Apparatus comprising a micro engineered structure and a capillary or other tube and a method for connecting the tube to the structure. The micro engineered structure is composed of at least one substrate 2 in which fluid flow channels 6 are formed, connecting to an aperture 12 into which the tube 14 is inserted. A sealant material is flowed into the aperture around the tube and then hardened in order to seal the tube within the aperture.

Abstract: An electrochemical cell sensing circuit for an electrochemical cell having a working electrode, a counter electrode and a reference electrode in an electrolyte, which in use, when a gas to be analysed is introduced into the cell, generating a current between the counter electrode and the working electrode, and a potential at a position in the electrolyte is sensed by the reference electrode.

Abstract: Glow discharge apparatus comprises a light-transmissive body (101) defining a cavity (102) containing neon or xenon gas. The glow discharge is powered by one or more electrodes (103) external to the cavity. The apparatus also comprises a secondary light source (104) for illuminating the neon gas to provide electrons in the cavity, thereby assisting discharge initiation in intermittent use, for example when controlled by a pulse time modulation drive circuit (107).

Abstract: A filter apparatus (1) has a digital FIR filter (8) divided into two or more sections (6, 12) with means (18, 20, 22, 24, 26, 40) for varying the filter function of each section (6, 12). The filter (1) has an input switch (2,4) and an output switch (28, 30,32) which includes a fader (28, 30, 32) to enable one or more section (6, 12) to be switched out of circuit without disrupting the passage of signals to be filtered through the other section or sections (6, 12) of the filter (8). The filter function of each section (6, 12) is adjustable when the section (6,12) is switched out of circuit.

Abstract: A method of identifying a data carrier such as a credit card, benefit card, access control card, identity card or stored value card, carrying data in the form of a plurality of rational number in a sequence, successive numbers having a marker between them, comprises a) measuring the distance from a fixed point on the data carrier to a given part of a marker, b) dividing this distance by the distance between corresponding give parts of successive markers, thereby obtaining a rational number, and c) subtracting this rational number from the number in the sequence adjacent the marker in a given direction, thereby obtaining a further rational number which is capable of identifying the data carrier uniquely.

Abstract: A method of encoding invisible identification code into an image, which is highly resistant to degradation across communications links, and which does not require the presence of the original image for decoding, comprises analyzing the image and determining strongly featured regions such as edges, and inserting code into such regions by altering the structure of the image in a predictable manner, as for example a concave elliptical insert centered on and aligned with an edge, which alteration is not visible to the eye. When decoding, area of concavity are determined, and a correlation is performed with a predicted insert function to assess whether code has been inserted. A hardware embodiment is described.

Abstract: In order to overcome problems with residual d.c. offset, and input signals with arbitrary timing, a drive circuit for a ferroelectric liquid crystal device includes a counter arranged for counting between first and second predetermined values in response to an input signal. The counter is designed so as to count in a first direction in response to a positive edge of the input signal and in a second direction in response to a negative edge of the input signal. Gating and latching circuits are responsive to the counting of the counter and the direction of count so as to provide appropriate positive or negative output voltage pulses for driving a ferroelectric liquid crystal device. An output stage comprising a bridge circuit is coupled via a step up transformer to the display device.

Abstract: A single mode resonant cavity is adapted to absorb energy via a single excitation mode in a plurality of overlapping absorption bands having different respective resonant frequencies, thereby increasing the resonant bandwidth of the cavity. The high Q-factor cavity may form part of a microwave powered catalytic converter for exhaust gas, and has the advantage that as the cavity warms up and physically expands the coupling efficiency between the cavity and a relatively narrow waveband microwave source remains good.

Abstract: An apparatus for displaying an image has a display area comprises a plurality of displays such as LCDs or CRTs each displaying a given part of the display area in a side by side arrangement facing in the same direction with gaps between them. A pair of arrays of converging lenses is provided in the path of light from the display area to the image. Each array comprises lenses having the same focal length, and lenses in respective arrays have different focal lengths. The arrays have different pitches and lie in parallel planes in an afocal arrangement. The arrays expand and/or laterally shift the given parts of the display area to form a viewable image of the whole display area in which the gaps between neighbouring parts of the image are less visible than the gaps between neighboring parts of the display area.

Abstract: Methods of controlling the brightness of a glow discharge which switches from a low brightness state to a high brightness state a given time after the start of an excitation pulse are described. In the first method, conventional pulse duration modulation produces a dimming ratio much greater than the ratio of duty factor variation. In the second method, a plurality of sets of pulses having different fixed durations but variable repetition rates are employed. In the third method, a plurality of sets of pulses having different relative durations have their pulse durations modulated in synchrony.

Abstract: A liquid crystal composition having a high order, tilted ferro-electric achiral Smectic I phase exhibiting a relaxed cone angle of greater than 20.degree. in the absence of high surface tilt alignment layers at temperatures in the range of 5.degree. C. to 40.degree. C. and includes from 90% to 99.9% by weight of a mixture of at least two achiral host compounds and from 0.1% to 10% by weight of a chiral dopant compound.

Abstract: Apparatus for blocking a d.c. component of a signal, comprises an electrically conductive signal path (1, 2) having a gap (3) in it preventing direct current flow across the gap, and an electrically conductive element (4) spaced from the path by a body (5) of dielectric material, the element (4) being located and dimensioned such that in use an a.c. signal is coupled from the signal path (1) into the element (4) at one side of the gap, and from tie element (4) into the signal path (2) at the other side of the gap. The apparatus optionally includes a quarter wavelength earthing strap between the signal path and ground potential. The apparatus includes means for providing an a.c. signal feed into a hazardous environment in an intrinsically safe manner.

Abstract: An apparatus forming a border for an image comprises a first pattern (3) and a further pattern (4) superimposed on but spaced from the fist pattern, the patterns comprising visually contrasting areas, overlying portions of the first pattern and the further pattern being such as to form a resultant pattern (5) appearing to lie in front of and/or behind the plane of the border. The first pattern and/or further pattern changes with time and comprises a liquid crystal panel comprising an array of addressable picture elements.

Abstract: In a three-slot addressing scheme for a liquid crystal optical modulator, where the data waveforms comprise a data section, a charge-balancing section and a further section, the form of the further section depends upon the sequence of data waveforms. The further section or pair of adjacent further sections comprises a pair of pulses of opposite polarities which charge-balance each other. The order in which these pulses occur in the pair enhances the effect of the adjacent data section to aid or inhibit switching as appropriate. This facilitates a shorter line address time.

Abstract: In order to facilitate diffusive transfer of an entity such as a solute between immiscible fluids and subsequent separation of the liquids without mixing, a method and an apparatus are disclosed and have first and second flow paths carrying first and second immiscible fluids on opposite sides of a foraminous sheet. The height of the apertures in the sheet is not greater than 200 micrometers (measured perpendicular to the width of the sheet and to the direction of fluid flow), and a stable interface is formed between the fluids within each aperture with a significant amount of fluid flow immediately adjacent the interface. Diffusive transfer takes place across the interface, and subsequently the fluids flow away from the region without mixing. The width of the flow paths measured perpendicular to sheet lies between 10 and 500 micrometers. The walls of each aperture may be parallel or tapered.

Abstract: Stereophonic sound reproduction apparatus comprising an input means (2) for producing binaural signals, cross-talk cancellation means, (10) loudspeaker means, (20, 22) headphone means, (26) and a switch means (12, 18, 24, 30, 32) which in a first position (plug 24 not inserted in socket 18) couples the binaural signals from the input means (2) to the loudspeaker means (20, 22) through the cross-talk cancellation means (10) and in a second position (plug 24 inserted in socket 18) renders the cross-talk cancellation means (10) inoperable and couples the binaural signals from the input means (2) to the headphones (26).

Abstract: A gas sensor including a substrate that is porous at least in a region thereof to permit permeation of gas. At least first and second porous electrodes are formed as planar elements on the substrate. The substrate is bonded to a housing in a peripheral area of the sensor. A portion of the first electrode extends into this peripheral area and is rendered non-porous to prevent the leakage of electrolyte therethrough.