Closed-Loop Control System:
A closed-loop control system is one in that control action is dependent on the outcome. Below figure displays an instance of a closed-loop control system. The control system manages water level in a storage tank. A system performs this task through incessantly sensing the level in the tank and adjusting a supply valve to add more or less water to the tank. A desired level is preset through an operator that is not part of the system.
Figure: Closed-Loop Control System