Abstract: There is provided an apparatus and method for encoding a code signal particularly into an audio signal. Previously as a result of data compression protocol codes hidden into “sync periods” have been degraded or lost as a result of, for example, low pass filtering. Sometimes, during quiet intervals codes were audible. The invention overcomes the problem of encoding a code into an audio signal by sampling the audio signal in order to determine its energy content and embedding the code into a suitable portion of the audio signal so that the code is hidden within a sufficiently energetic portion of audio signal. The advantage is that code is never audible.

Abstract: A method of forming a liquid crystal polymer layer includes: coating a substrate with a release layer; coating the release layer with an alignment layer capable of aligning a liquid crystal polymer layer; coating the alignment layer with a layer of a liquid crystal polymer material, thereby forming a liquid crystal polymer layer in which the molecules have a predetermined orientation; solidifying the layer of liquid crystal polymer; and dissolving the release layer in a liquid which does not harm the solidified liquid crystal polymer layer to form a self supporting film. The release layer and alignment layer can be combined into a single layer, such as for example a layer of polyvinyl alcohol which may be dissolved in water. Thicker or multi-layer films can be fabricated by using the first solidified layer as an alignment layer for a subsequently deposited liquid crystal polymer layer.

Abstract: A method of processing a plural channel audio signal representing a three dimensional sound-field for generation by respective left and right loudspeakers arranged at a given distance from a listener, including: a) choosing a distance between said loudspeakers and said listener; b) determining from this chosen distance an optimal amount of transaural acoustic crosstalk compensation, the optimal amount being a function of the chosen distance; and c) applying said optimal amount of crosstalk compensation to said left and right channels. The optimal transaural crosstalk cancellation is preferably achieved using a near ear response transfer function and a far ear response transfer function which asymptotically approach different values at low frequencies. The method may further include choosing an angle between the left channel loudspeaker and the right channel loudspeaker, and determining from both the chosen angle and the chosen distance an optimal amount of transaural crosstalk compensation.

Abstract: The invention relates to gas sensors, particularly electrochemical gas sensors. The reliability of such gas sensors has been ascertained by regular tests, which involve exposing a sensor to a gas for test or calibration purposes. However, it has been difficult to provide a known quantity or concentration of gas. Another problem has been that blockage of a gas inlet has rendered the gas sensor unreliable. The invention provides a gas sensor having a self test capability and first and second electrodes, arranged so that test gas arrives at a separate instant at each electrode so as to generate two electric currents, the ratio of which currents provides an indication of the status of at least one electrode.

Abstract: An optical modulator comprises a layer of a ferroelectric liquid crystal material being provided between an integrated circuit and a light transmissive sheet. The light transmissive sheet and the integrated circuit carry respective electrodes which define selected areas of said layer. In use, the selected areas are addressed with data according to an addressing sequence which is repeated in successive time periods. The optical modulator includes means for providing a plurality of voltage pulses to the one or more electrodes being carried by the light transmissive sheet in a given time period, thus enabling a time dithered greyscale driving scheme to be used.

Abstract: A stereo sound expander reproduces a realistic sound image in three dimensions by coupling modified and unmodified stereo signals. By not modifying a Head Related Transfer Function (HRTF) for one signal and equalizing the HRTF for the other signal, a flattened frequency response is produced with no tonal changes, but with a high degree of spatial accuracy. Resultant output signals may be used to generate binaural signals or can be fed into crosstalk cancellers.

Abstract: A method of synthesizing a three dimensional sound-field using a pair of front and a pair of rear loudspeakers, including: a) determining the desired position of a sound source; b) providing a binaural pair of signals corresponding to the sound source using an HRTF filter; c) providing the left signal of said binaural pair of signals to both the left front and left rear loudspeakers through a front and a rear gain control means respectively; d) providing the right signal of said binaural pair of signals to both the right front and right rear loudspeakers through a front and a rear gain control means respectively; e) controlling the ratio of the front signal gains to the rear signal gains as a function of the azimuth angle of the sound source; and f) performing transaural crosstalk cancellation on the front and rear signal pairs through respective transaural crosstalk cancellation means.

Abstract: Apparatus for sampling a liquid, said apparatus comprising: i) a sampling device capable of automatically taking a known volume of liquid from a source; ii) fixing means connected to said sampling device and removably attachable to a solid phase extraction (SPE) unit, the fixing means being arranged such that liquid taken from a sample by the sampling device is passed directly through the solid phase extraction unit; iii) a reading device able to read labels on an SPE unit attached to said fixing means; iv) a controller arranged to log codes based upon a signal from the reading device, and thereafter issue instructions to an operator and/or operate the sampling device to take an appropriate volume of liquid in response to a signal from said reading device. Methods of sampling using the apparatus are also claimed. These are useful in, for example analysis methods.

Abstract: A gas sensor including a housing containing at least a sensing electrode, a counter electrode, a test electrode, and electrolyte means in contact with such electrodes. The housing permits gas from the environment to flow to the sensing electrode. The gas sensor is operable either in a normal mode of operation in which potentials are applied to the electrodes for detecting when a gas to be sensed is present at the sensing electrode, or in a test mode of operation in which potentials are applied to the electrodes so that the test electrode generates a gas which flows to the sensing electrode to enable an indication whether the sensor is operating correctly.

Abstract: An apparatus for locating a plurality of articles for laser marking comprising a support plate (16) having a plurality of apertures (18) extending from a first surface of the plate (15) to a second surface of the plate (17). The apertures are dimensioned to receive said articles (12) at the first surface of the plate (15), so that the at least a portion of the article is exposed through the aperture (18). Preferably apertures are defined by tapering walls. In use a laser (30) is directed towards a protruding portion of the article (21). The extent to which the articles protrude through the aperture (18) is significantly less than the variation in diameter of articles (12) to be laser marked. This eliminates the need for the laser to focus on individual articles (12).

Abstract: An apparatus for reading permanently structured magnetic records having a first coercivity, comprising an oscillator having an inductive read head that is coupled to a circuit arrangement. At least one side of the read head sees an impedance that is larger than the impedance of the read head over the range of frequencies of interest, such that the read head provides an electrical signal in response to magnetic records having a second coercivity that is higher than the first coercivity (typically 2,000 to 5,000 oersteds). The electrical signal is derived from the voltage across the read head, which is preferably detected by a differential integrator that subtracts the voltages on either side of the read head to give a voltage difference, and integrates this difference over time.

Abstract: An apparatus for displaying an image in space and for providing a background image behind the projected image having an image generator and optical system for projecting an image of an object in an image plane suspended in space. A partially light-transmissive screen is located between the image generator and optical system and the projected image. The screen contains a pattern of juxtaposed light-transmissive regions, through which the image is projected, and regions which are not light-transmissive (ie, substantially opaque areas or reflective surfaces). The background image is printed, or painted, on the opaque areas on the side of the screen remote from the image generator optical system. The screen may be made by printing the background image on opaque areas on a translucent or transparent film, or by printing the background image on a foraminated or perforated opaque sheet.

Abstract: A method of synthesizing an audio signal having left and right channels corresponding to an extended virtual sound source at a given apparent location in space relative to a preferred position of a listener in use is described. The information in the channels includes cues for perception of the direction of said virtual sound source from the preferred position. The extended source comprises a plurality of point virtual sources, the sound from each point source being spatially related to the sound from the other point sources, such that sound appears to be emnitted from an extended region of space. If the signal from two sound sources is the same, they are modified to be sufficiently different from one another to be separately distinguishable by a listener when they are disposed symmetrically on either side of the listener. This modification can be accomplished by filtering the two point sources using different comb filters.

Abstract: The apparatus comprises an object for display, a retro-reflector receiving light from the object, a beam-splitter in a path for light from the object to the retro-reflector, and a Fresnel lens (having no point of central symmetry) between the beam-splitter and the retro-reflector. The beam-splitter makes an oblique angle to the direction of propagation of the light, such that it transmits some light and reflects the rest. Light from the beam-splitter passes through the lens to the retro-reflector, which reflects it back through the lens to the beam-splitter. This retro-reflected light is reflected and/or transmitted by the beam-splitter to form a real image suspended in space. The type of Fresnel lens used in the apparatus improves viewability because unwanted reflections from the surfaces of the lens are shifted such that they are no longer visible when viewing the suspended image.

Abstract: A gas sensor is described which is particularly well suited as a carbon monoxide (CO) sensor in a self test gas sensor. The sensor includes a number of aspects which may or may not be used in conjunction with one another. A first aspect is an embodiment which reduces electrical interference (or cross-talk) between a test or gas generating cell and a sensing cell. In one embodiment, baffles are provided to prevent cross-talk. In another embodiment a switching circuit ensures that a test gas generator is operational only when the gas sensor is disconnected from a current source. A second aspect is an embodiment which includes an improved wick which is in close proximity with an electrode and ensures electrolyte is always in contact with the electrode. In an alternate embodiment a solid polymer electrolyte is used between the electrodes. A third aspect is an improved catalyst which reduces the reaction energy and thereby renders the sensor more sensitive. The catalyst is also cheaper than platinum.

Abstract: Apparatus for labelling a stereophonic signal includes a plurality of notch filters having selected center frequencies to form notches at the selected frequencies in the channels of a stereophonic audio signal. Code generating components produce a coded label signal in the form of one or more code words, with the code being formed of selected signal bursts at the selected frequencies. The coded label signals are inserted into both channels of the audio signal, in the notches formed by the notch filters. The code signal amplitude bears a predetermined relationship to the audio signal amplitude in each channel.

Abstract: Apparatus for displaying an image suspended in space comprises an object (1) for display, a retroreflector (2) receiving light from the object, a beamsplitter (3) in a path for light from the object to the retroreflector, and a concave mirror (4) between the beamsplitter and the retroreflector. The beamsplitter makes an oblique angle to the direction (6) of propagation of the light such that it transmits some light. Light from the beamsplitter is reflected by the mirror to the retroreflector which reflects it back via the mirror to the beamsplitter. This retroreflected light is reflected by the beamsplitter to form a real image (5) suspended in space. The use of a concave mirror improves viewability over apparatus including a converging lens because unwanted reflections from the surfaces of the lens are eliminated.

Abstract: Apparatus for dispensing a predetermined volume of a liquid (18) comprises a reservoir (12) for the liquid, a channel (13) provided with an outlet (16) for conveying the liquid (18) from the reservoir to the outlet, and means for generating a pulse of gas. The apparatus is arranged such that the flow of gas causes a predetermined volume of liquid to be ejected from the outlet. The outlet comprises a pair of openings in the channel which face one another, the liquid being retained between the openings by surface tension in the absence of a flow of gas. The gas flow is directed towards one of said openings in use. The apparatus may be used to dispense volumes of a liquid reagent in the range 1 nl to 2 &mgr;l. The apparatus avoids contamination of the liquid, and dispensing head construction allows devices to be low cost disposable units. The apparatus is less sensitive to liquid viscosity than existing devices.

Abstract: A laminated artificial pinna having a concha, fossa and auditory canal. The auditory canal is constructed and arranged relative to the concha so that the distance from the center of the entrance of the auditory canal to the rear wall of the concha lies within the range of 15 mm to 20 mm, the distance from the center of the entrance of the auditory canal to the concha floor lies within the range of 9 mm to 15 mm, and the alignment of the turning point with the center of the entrance of the auditory canal is substantially horizontal.

Abstract: An electrochemical cell in the form of first and second sheet members (2,12) at least one of which is gas permeable on which is disposed one or more planar electrodes (4,6,8). Peripheral regions of the first and second sheet members (2,12) are sealed together to form a sealed envelope or reservoir containing electrolyte. Electrical connection means (41,61,81) extend from each of the electrodes (4,6,8) across the sealing of the sheet members (2,12) to provide external electrical connection.