Definition extracted with permission from Simon, Fritz, et al, Family Process, Inc.: Language of Family Therapy: A Systemic Vocabulary and Source Book (Family Process Press Series)
This theory (located within the field of cybernetics) concerns itself with the structures and functions that determine the stability and development of dynamic systems. In a control system, the values of a variable quantity are controlled, either held constant or varied to conform to a prescribed norm. In this broad sense, living organisms contain numerous natural control systems, such as body temperature and acidity. The application of control theory in modern technology is far advanced, as in the development of computers, but it is still relatively primitive and speculative for biological systems, and especially for social systems. On a theoretical level, the function and structure of control systems is concerned with the transmission and processing of signals and/or information (information theory). The two fundamental types of control systems are feedback (closed loop) and feedforward (open loop) (feedback loop).