DMX is an acronym for Digital Multiplex, a protocol developed by the United States Institute of Theatre Technology (USITT) in 1986. DMX provides a digital communication method allowing up to 512 DMX lighting channels to be connected and operated with a master controller. Basic DMX lighting fixtures contain one DMX channel, while moving or special effects lights -- also known as intelligent lights -- contain two or more DMX channels for control of various functions.
DMX devices are connected with DMX 3-wire cables with XLR 3-pin connectors, with some high-end systems using 5-wire cable with 5-pin connectors. Device hookup begins with the DMX controller, continuing to each DMX light or power supply in daisy-chain fashion -- intelligent lights contain power supplies, while standard lights are plugged into a DMX power supply or "dimmer pack."
Each channel used by lighting fixtures and power supplies is assigned a DMX address number -- the basis for DMX control protocol used by Wybron and other manufacturers. Addresses are assigned by the lighting engineer via manual DIP (dual in-line package) switches or digital keypads installed on DMX-equipped lights and devices. A DMX address chart is used to assign devices to controller channels using binary numbers in multiples of three, using zero as the starting point.
Prior to DMX, manufacturers were free to use proprietary wiring and controllers. This not only discouraged intermingling of competitor products, but created operational learning curves among touring production engineers and technicians using unfamiliar venue or rental company lighting. The DMX protocol has been adopted internationally, with fixtures, cables and controllers familiar to touring professionals. Other DMX advantages over older technology include: lower cable voltage requirements, readily available cables and connectors and the ability to control complex intelligent lighting from the same controller as simple fixtures.