Abstract: A lighting control system which comprises an AC mains power point, power distribution means coupled to the AC mains, a dimmer assembly comprising one or a plurality of co-located dimmer circuits each coupled to the distribution means to receive AC power therefrom, and each comprising an output port developing an AC power signal of frequency corresponding to the AC mains, each said dimmer circuit comprising a current path between the distribution means and the output port, a switching means located in the current path so as to controllably interrupt passage of current, switch driving means supplying a control signal to the switching means to cause it to interrupt the current path a multiplicity of times within each AC half cycle, and filtering means in the current path between the switching means and the output port arranged to smooth the current therethrough, the filtering means being arranged to attenuate current components at the frequency of operation of the switching means, and not substantially to attenu

Abstract: In a lighting power controller having a controllable switch (such as a thyristor), in order to compensate for perturbations in the mains supply waveform, the waveform is analysed and a table is set up of thyristor firing angle against output RMS voltage. To obtain a desired output RMS voltage, the thyristor is fired at the angle indicated by the table.

Abstract: A lamp assembly particularly for a luminaire comprising a lamp having a light emitting member of generally torroidal shape and a reflector positioned and shaped to reflect light received from the light emitting member through the central opening. The light emitting member is preferably a filament of an incandescent lamp. The reflector has a cross-section comprising first and second arcs which are substantially symmetrical with respect to a line joining the center of the reflector and a point substantially at the centre of the torroidal member and the shape of the reflector is that described by rotating said arcs about said line. The arcs may be elliptical or circular for example with their foci or centers positioned to achieve the required effect.

Abstract: A lamp assembly particularly for a luminaire comprising a lamp having a light emitting member of generally torroidal shape and a reflector positioned and shaped to reflect light received from the light emitting member through the central opening. The light emitting member is preferably a filament of an incandescent lamp. The reflector has a cross-section comprising first and second arcs which are substantially symmetrical with respect to a line joining the center of the reflector and a point substantially at the center of the torroidal member and the shape of the reflector is that described by rotating the arcs about the line. The arcs may be elliptical or circular for example with their foci or centers positioned to achieve the required effect.

Abstract: In a lighting power controller having a controllable switch (such as a thyristor), in order to compensate for perturbations in the mains supply waveform, the waveform is analyzed and a table is set up of thyristor firing angle against output RMS voltage. To obtain a desired output RMS voltage, the thyristor is fired at the angle indicated by the table.

Abstract: An electrical unit such as a lighting dimmer pack incorporating one or more semi-conducting switching devices such as triacs or thyristors, wherein the usual insulated mounting base (18) of the triac (30) is in turn mounted on the unit casing via an electrically insulating heat conductor, and the said mounting base is connected to the phase or neutral conductor (52), preferably the latter. In a preferred arrangement, a plurality of triacs are clamped by a printed circuit board which provides the connection from the triac bases to the neutral conductor.

Abstract: A stage lighting control system having a main processor unit and a portable desk controller, wherein a local microprocessor is provided in the portable desk controller to scan the dimmer control contacts in the desk and to transmit changed state control data to the main processor as an asynchronous serially coded signal on a low capacity link which enables the controller to be conveniently located remote from the main processor. Changed display data is developed by a visual display unit (V.D.U.) interface in the main processor for transmission on the low capacity link as standard composite video to a V.D.U. at the desk. Output to the dimmers circuitry is through an expansible plurality of output channel processors controlling groups of dimmers for efficient data formatting. Lighting level information is recorded in accordance with a channel code, patching means being provided to enable differing arrangements of dimmers circuitry to be controlled in accordance with the recorded lighting level information.