A mode of control used to control a process in which the change in the controller output is proportional to the time integral of the deviation. The (p. 198) control action recognizes not only the magnitude of the deviation, but also the time during which the deviation occurs. Integral action is limited in application to processes of small capacitance and fast responses. It is therefore rarely used alone but instead is more frequently used in combination with proportional control. Integral action is the only mode of control that will bring the controlled variable back to the set point.