This is understood as the part of the overall control system of a plant, which is to control the compressed air or hydraulic fluid. in terms of direction, strength and pressure potential from the pump to the cylinder (motor). Its to the signal area in the case of electrical signal processing is formed by electrically actuated valves (solenoid valves, proportional valves, servo valves) as .
The total number and functionality of the valves depends on the task formulation. Its order and interconnections are specified in the circuit diagram.