Abstract: A ferroelectric liquid crystal device has a first state (T.sub.X1) of maximum transmission, a second state (T.sub.X2) of minimum transmission and a value of voltage pulse width (t.sub.S) and voltage pulse height (V.sub.S) sufficient for a switching pulse to switch the cell from the first state (T.sub.X1) to the second state (T.sub.X2) or vice versa. A method of controlling the transmission of electromagnetic radiation through the ferroelectric liquid crystal device comprises the step of applying, for a time period greater than said value of pulse width (t.sub.S), a plurality of consecutive controlling pulses of one polarity. Each controlling pulse is itself of insufficient pulse height and pulse width to switch the cell from the first state (T.sub.X1) to the second state (T.sub.X2) or vice versa.

Abstract: An electrodeless discharge tube containing an ionizable fill, the tube having a first portion for insertion in a launcher and a further portion separated from the first portion by a partition wall. Hence a discharge can be excited in the further portion because a surface wave can propagate through the wall separating the first and further portions.

Abstract: A sealing composition is provided for joining crystalline ceramic or cermet parts, e.g. in an arc tube for a discharge lamp. The sealing composition comprises, as starting materials, a mixture of alumina (Al.sub.2,O.sub.3), silica (SiO.sub.2) and magnesia (MgO), the mixture comprising in the ranges of from 22% to 24.5% by weight of Al.sub.2 O.sub.3, from 45.5% to 49.5% by weight of SiO.sub.2, and from 26.0% to 32.5% by weight of MgO. The sealing composition contains less than 40% by weight, of the mixture, of the crystalline phase .alpha.-Cordierite when subjected to the following test procedure.(i) sintering the mixture at 1200.degree. C. for 10 hours to produce a friable lump which is crunched and heated at 1550.degree. C. for 2 hours while the glass is in a molten condition;(ii) pouring the resulting material into water to form a brittle frit and, after drying at 160.degree. C., grinding the glass to a powder particle less than 180 .mu.

Abstract: A single channel optical recording system is described, which system does not require a second rotating optical element. The system uses focus error correction components located outside the rotating drum. Light transmitted to and from the drum is at all times axially symmetric, thus circumventing the problem of image rotation. Lateral error correction takes place entirely within the drum, requiring only the transmission of d.c. electrical power across the rotating interface. Preferably the physical distribution of optical components within the drum is symmetric to ensure mechanical balance. A dual beam tracking system to write data in compact form in a single-channel optical tape recorder is also described. The tracking is achieved in the drum and without any additional optical elements. Passive or active alignment of the two beams before entering the drum is achieved using an extended anamorphic prism pair and without introducing additional optical surfaces into the beam path.

Abstract: A display device has a lattice of pixel elements each selectably settable. A method of operating the display device comprises the steps of receiving a signal representing a picture for display during a display period and illuminating the lattice to produce, during a first interval within the display period, a first light output from the lattice having a first predetermined color characteristic and to produce at least one additional light output from the lattice. Each said additional light output has a different predetermined color characteristic and a respective interval within the display period separate from the first interval. The method further comprises the step of time-multiplex addressing blocks of pixel elements a plurality of address times during each interval.

Abstract: An electrodeless discharge tube containing a fill which comprises a metal carbonyl complex. Such a complex will be sufficiently volatile to produce a vapor pressure in a discharge tube in which a discharge can be generated. The discharge so generated emits a mixture of visible and infra-red radiation.

Abstract: An apparatus for monitoring the marking of a recorded signal includes a data store containing marking information and a code selector for selecting any one of three orthogonal codes for marking the recorded signal and a demodulator for demodulating the marked signal and comparing this with the orthogonal codes. The demodulated marked signals are then fed to matched filters and accumulators wherein the marking process may be repeated dependent upon the value of the accumulation.

Abstract: Coating apparatus for a thin plastics web comprises a coating deposition station for applying a coating to the web by vapor deposition and a support for supporting the web at the coating deposition station. The apparatus includes a device for urging gas into the region where the thin plastics web converges with the support to improve the thermal coupling between the web and the support and also to reduce the coefficient of friction between the web and support. The gas enables the coating to be applied by vapor deposition at coating speeds of up to 90 meters per minute without deformation of the thin plastics web.

Abstract: A thermal imaging device includes an array of pyroelectric detector elements, supported by an array of pillars, the pillars also being effective to enable the passage of electrical signals between the detector elements and an electrical signal processing means. Each pillar is separated from a respective detector electrode by an elongate electrically conductive strip. The device includes areas of infra-red absorbant material effective to conduct heat from non-electroded parts of the device into adjacent pyroelectric detector elements.

Abstract: A discharge tube arrangement comprises an excitation device and a discharge tube made of a light-transmissive dielectric material and containing a fill. The excitation device is suitable, when energized with radio frequency (r.f.) power, for exciting surface waves in the discharge tube. The excitation device includes a launcher and a plurality of electrical components associated with the supply of r.f. power to the launcher and constituting at least one of an impedance matching network and a part at least of means to generate r.f. power. This plurality of electrical components is positioned in the launcher between its inner and outer tubes.

Abstract: A discharge tube arrangement includes a discharge tube containing a fill and means for generating a discharge in the fill from a source of radio frequency (r.f.) power. An electrically conductive structure surrounds the discharge tube. The electrically conductive structure is formed of a plurality of waveguides which extend outwardly from the discharge tube. One or more waveguides has a cross-sectional area that increases with separation from the discharge tube. Each waveguide is dimensioned to support the propagation of electromagnetic radiation above a cut-off frequency.

Abstract: To provide stationary or mobile radar with the capability of measuring the true range profile, a radar system includes a voltage oscillator coupled to a duplexer via a pulse modulation circuit. A digital control circuit provides a sweeping 500 Mhz frequency (F) of 6N successive batches of pulses being incremented in steps of F/6N. Returns received in response to each transmitted pulse are then combined in a mixing circuit with the signal from the local oscillator to generate a signal IF; each signal is summed with signals for the same range cell derived from earlier pulses transmitted at the same frequency; thereafter the signals pass through a FFT circuit.To maintain the "dissected" spectrum centered at the 2N.sup.

Abstract: A discharge tube arrangement for use as a light source includes a discharge tube made of a light-transmissive dielectric material and containing a fill. An excitation device for exciting surface waves in the discharge tube comprises an r.f. power generator and a launcher. The launcher is formed as an inner tube, an outer tube coaxial with the inner tube and first and second end walls, at least one of the first and second end walls having an aperture for receiving the discharge tube. A launcher gap extends axially from a first end of the inner tube and there is also a further gap. The outer tube and the first and second end walls form an unbroken electrically conductive path to provide an r.f. screening structure around the inner tube.

Abstract: A disposable cartridge for use in a clinical sensing arrangement interfaces electrically with a host instrument capable of responding to electrical signals generated by detector devices incorporated in the cartridge upon exposure to calibrant fluids and/or clinical fluids under examination. The cartridge includes a passage linking a reservoir of calibrant fluid to the detector devices and further linking the device to a closed container for fluid which has been conveyed past the devices. A fluid under test can be introducted into the cartridge through the passage wall at a location disposed between the reservoir and the detector devices.

Abstract: A discharge tube arrangement comprises a launcher and a discharge tube positioned in part within the launcher. When the launcher is energized with radio frequency (r.f.) power, surface waves are excited in the discharge tube which contains a fill. An electrically conductive structure extends along the discharge tube and is connected to an earth when in use. The structure is separated from the discharge tube by a radial distance such that, in use, the discharge tube produces an increase in total light output over the total light output of a discharge tube not having this structure. The structure comprises an insufficient quantity of material to obscure this increase in total light output.

Abstract: A radio frequency transmission and reception system, for use as an active decoy, includes a receiver 10, a transmitter 12 and a signal generator 20 for providing wideband noise signals for transmission during the interpulse period of pulsed signals transmitted by the transmitter 12. A feedback circuit 21, including an adaptive transversal filter 23 combines signals for transmission with output signals from the receiver to adaptively modify the wideband signals in the signals for transmission so as to render the receiver 10 substantially insensitive to received signals which are derived from the transmitter.

Abstract: A method is disclosed for addressing a matrix-array type liquid crystal layer. The cell has a plurality of pixels which are defined by regions of overlap between two sets of electrodes which sandwich a liquid crystal layer, each pixel having two states. The response time for switching between the two states is dependent upon the voltage across the liquid crystal layer, with a minimum occurring at a particular voltage. The method includes applying a strobe waveform to a selected member of a first set of the electrodes while a data waveform is applied to each member of the second set of electrodes. A waveform for switching a pixel defined by the selected member comprises a switching pulse of a given voltage magnitude and given duration. A waveform for not switching a pixel defined by the selected member comprises a non-switching pulse of a voltage magnitude greater than the given voltage magnitude of the switching pulse and a duration less than the given duration of the switching pulse.

Abstract: A recording drum assembly comprises a cylindrical drive shaft 1, a drum 2, and an annular disc 4 of resilient material, such as spring steel, located between the drive shaft 1 and drum 2 and substantially coaxial with the drum 2. The disc 4, by elastic deformation when engaged by the drive shaft 1, provides axial alignment of the drum 2 and drive shaft 1. A portion of reduced diameter may be provided on the drive shaft 1 to facilitate removal of the drum 2 from the drive shaft. Furthermore, the annular disc 4 may be used to support the drum 2 during machining of the drum outer surface to ensure coaxial alignment.

Abstract: An infra red radiation modulator comprises a p type silicon substrate 1 having spaced n type and p type doped regions 2, 3 having respective doping concentrations of approximately 10.sup.20 and 10.sup.16 /cm.sup.3. A signal source 11 provides a bias voltage between the doped regions 2,3 via electrodes 4 for modifying the concentration of free carriers in the substrate between the doped regions and therefore the response of the modulator to incident infra red radiation. By appropriate control of the bias voltage the modulator can be caused to modulate, chop, filter or spectrally scan the incident radiation.