Stage lighting control system

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.