The key words in this definition are move and great accuracy . Servos may be found in such varied applications as moving the rudder and elevators of a model airplane in radio-controlled flight, to controlling the diving planes and rudders of nuclear submarines. Servos are powerful. They can move heavy loads and be remotely controlled with great precision by synchro devices. They take many forms.
Servo systems are either electromechanical, electrohydraulic, hydraulic, or pneumatic.
Whatever the form, a relatively weak signal that represents a desired movement of the load is generated, controlled, amplified, and fed to a servo motor that does the work of moving the heavy load. A control system is a group of components that are linked together to perform a specific purpose. Generally, a control system has a large power gain between input and output. The components used in the system and the complexity of the system are directly related to the requirements of the system's application. The reason for quicker response and greater accuracy is that an automatic feedback system informs the input that the desired movement has taken place.