Abstract: A repeater for use in a control network includes isolating transformers at its root input/output and at a plurality of branch input/outputs. There is a line receiver and a line driver circuit associated with each of the isolating transformers. To determine the direction of transmission of signals through the repeater, there is a common mode voltage detector which detects a common mode voltage imposed on the wiring to the root side of the root transformer. A corresponding common mode voltage is imposed by the repeater on the branch side of each of the branch transformers. The repeater also includes a logic circuit for testing the validity of signals received from the branches and ensuring that only valid signals are passed to the root transformer.

Abstract: A stage lighting lamp unit includes a processor for receiving control data from a remote console. Beam orientation data for the lamp unit is passed to the lamp in the form of the x, y and z co-ordinates of a point in space through which the beam is to pass. The processor divides the required lamp travel into a number of stages dependent on execution duration data sent with the position data, and calculates, for each stage, a new value for pan and tilt angles for the lamp. These values are passed to pan and tilt controlling co-processors which control servo-motors for pan and tilt operation. The lamp unit also incorporates a rotatable shutter for interrupting the lamp beam when required. The shutters of all the lamps in a system can be instructed from the remote console to open and close in synchronism, thereby providing a stroboscopic effect.

Abstract: A color cross-fading system for a luminaire includes two filter disks or strips each provided with a multi-layer filter coating to provide a dichroic filter effect. In each case the thickness of the coating layers varies continuous along a gradient axis of the filter disk or strips. One disk acts predominantly as a long wave pass filter and the other act predominantly as a short wave pass filter, but each disk has an essentially "complex" characteristic enabling a very wide range of different colors to be obtained by cumulative subtractive filtering, by varying the positions of the two disks or strips relative to an optical axis.