The phrase distributed control system (DCS) usually refers to a type of manufacturing system in which the control of the various divisions are spread out, rather than centralized in one location. The term may also be used more generally to refer to any decentralized or dynamic system. The distributed control system is often used in industrial automation and safety systems because the individual component systems can be controlled without affecting the whole system.
In the simplest form, a distributed control system shifts the control of each point in a manufacturing system to that section. For example, if an industrial safety system is protecting four rooms using automated sprinklers and fire doors, the system will take over if one room is comprimised. When the fire alarm is triggered, the fire doors for the affected room close and the sprinkler system begins to function. In a distributed control system, this response is limited only to those rooms in which a threat is actually present. If the safety system were centrally controlled, the fire suppression response would have occurred in all four rooms, instead of isolating the effort to a single room.
While the idea of a centrally controlled system that offers simultaneous protection to an entire building may seem like a good idea, closer inspection may reveal certain advantages that can be offered by a distributed control system. In the scenario provided, all four rooms of the building would have been flooded with water as a result of the sprinkler system activation. If one of these rooms held all of the company's computer networking equipment, one stored products, a third housed production, and a fourth raw materials, all of these materials would have been destroyed. By utilizing a distributed control system, the response to the fire alarm could have been directed precisely to the room where the fire occurred, limiting collateral damage.
The distributed control system can also be used to manage the manufacturing processes of various segments of an operation. Using this system, a machine failure in one section of an assembly process does not necessarily impede the function of the entire line. When each section is independently controlled, the other stations can continue to work while the affected machine is repaired. This ability to bypass sections makes the distributed control system a very valuable asset in manufacturing set-ups that require routine maintenance of equipment.