Deliver power to the lighting positions. Design of a lighting control system starts with the way electricity will be delivered to various lighting positions in the theater. Most theaters use long gang boxes made up of many evenly spaced power outlets that are permanently installed at the lighting position. Long, thick cables connect the gang boxes to a central power head. The power head is usually located near a power breaker box on the stage level, usually inside a mechanical closet. Installing a new system for lighting control is the work of an expert and is usually done at the time the theater or auditorium is being constructed. But a new lighting system can be retrofitted into a theater at any time.
Control the power flow with dimmers. Rheostat dimmers control the amount of power sent to each outlet along a gang-box line. Dimmers are mechanical devices that narrow or widen the power flow to the instruments. Each gang-box outlet in the theater is numbered for identification purposes---1 through 120, for example. These outlets are then patched into a specific dimmer that is also numbered. A single floodlight instrument located at a front-of-house position might carry the identification number "78 on 30," meaning "Outlet box 78 is controlled by Dimmer 30." The lighting designer schedules the control of lighting during a performance using this information.
Control the dimmers from afar. In earlier times the dimmers were controlled from a massive panel located offstage in the wings. Today most control head consoles or lighting boards are located at the back of the house, usually inside a soundproof booth, and are the size of an electronic piano keyboard or smaller. A signal cable leading to the dimmers connects the lighting board so the dimmers can be "played" remotely by a board operator in the booth. Today this control board is at least partially or fully automated with the help of a special computer built into the board. Each dimmer is programmed into the board to be manipulated by a slider channel represented on the board. Most modern light boards offer at least 48 channels that can be used for dimmer assignments. Fully computer-assisted systems can be programmed to remember complex dimmer assignments and can play back prerecorded lighting cues. Board operators can also manually operate these sliders to control the lighting instruments.