 An actuator is a component of a machine that is responsible for moving and controlling the mechanism or system, for example by opening the valve. In simple terms, it is a mover. An actuator requires a control signal and a source of energy. The control signal is relatively low energy and may be electric voltage or current, pneumatic or hydraulic pressure, or even human power. Its main energy source may be an electric current, hydraulic fluid pressure, or pneumatic pressure. When it receives a control signal, an actuator responds by converting the signal's energy into mechanical motion. An actuator is the mechanism by which the control system acts upon an environment. The control system can be simple affix mechanical or electronic system software based e.g. a printer driver, robot control system the human, or any other input.