Abstract: A communications network router is described for secure routing of calls between domains of different classification levels. The network router includes a first communications port arranged to receive a first communications channel of a first domain, a second communications port arranged to receive a second communications channel of a second domain, a switch apparatus arranged selectively to connect the first port to the second port to establish a communications link between the first and second domains. The first domain has a different level of classification to the second domain.

Abstract: A bistable nematic liquid crystal device is addressed by application of a row waveform to successive row electrodes of an x, y matrix of pixels whilst one of two data waveforms are applied to each column electrode. The row waveform has a period of two or more time slots (ts), with two dc pulses of opposite amplitude for causing a switching to a dark state, and two dc pulses of opposite amplitude for causing a switching to a light state. The data waveforms have the same period as the strobe with dc pulses of opposite amplitude and combine with the strobe pulses to switch the device. The device can be addressed in two field periods, one field switching to a dark state, the other field switching to a light state. Alternatively, the device can be blanked to the dark state then selectively switched to the light state. When blanking is used, the row waveform has blanking de pulses placed a short time before selective switching to reduce overall addressing time.

Abstract: When a ferroelectric liquid crystal display (FLCD) panel is addressed in such a manner as to cause adjacent or successive pixels to display different levels of greyscale, the viewer may perceive a pseudo edge effect caused by the perceived error in the transmission level at the transition between the two grey levels. In order to decrease this perceived error, the panel is addressed such that, at the transition between the two grey levels, for example between the grey levels “3” and “4”, the most significant bit of the addressing scheme incorporates an analogue grey level, for example a half level. This results in a perception level exhibiting a lower absolute error in the relative grey level than would be obtained if no special measures were taken to compensate for the perceived error at the transition. This compensation technique is applicable to addressing schemes utilizing temporal dither (TD) as well as spatial dither (SD).

Abstract: A light modulating device, such as a ferroelectric liquid crystal display (FLCD) comprises an addressable matrix and modulating elements or pixels and associated circuitry for selectively addressing each element in a series of addressing frames in order to vary the transmission level of each element relative to the transmissions levels of the other elements. Such addressing utilises a temporal dither addressing scheme for addressing at least part of each element within each frame with different combinations of temporal dither signals applied to separately addressable temporal bits within the frame to produce different transmission levels. In order to enable a large number of grey levels to be produced whilst limiting the perceived errors at transitions between different grey levels, the temporal bits are addressed in a first order in a first frame (or in a first spatial location) and in a second order, which is different to the first order, in a second frame (or in a second spatial location).

Abstract: The invention provides a ferro-electric liquid crystal display (FLCDs) with reduced voltages requirements for driver circuits. This enables standard drivers circuits designed to rms address twisted nematic type of displays, to be used for FLCDs. Displays are formed by cells containing smectic liquid crystal material. The cell walls are surface treated and carry e.g. row and column electrodes forming an x,y matrix of addressable display elements. The smectic liquid crystal material switches between two states upon application of a dc pulse of appropriate amplitude, polarity, and time. Addressing waveforms are strobe waveforms, e.g. two pulses of opposite polarity in successive time slots, applied to each row in turn. Data waveforms are, e.g. dc pulses of alternate polarity with each pulse lasting one time slot ts. Two data waveforms are needed to switch between the two states; one data waveform is the inverse of the other. Typically a strobe waveform pulse may be 50 volts.