An actuator is a machine component responsible for moving and controlling a mechanism or system by opening a valve or carrying out a similar function. In essence, an actuator is a ‘mover.’ To function, an actuator requires a control signal and a source of energy. The control signal can be electric voltage or current, pneumatic or hydraulic fluid pressure, or even human power, and is relatively low energy. An actuator's energy sources can be electric current, hydraulic pressure, or pneumatic pressure. Upon reception of a control signal, the actuator responds by converting this energy into mechanical motion.