English: Two pneumatic rack & pinion actuators (AutoMax SuperNova) are used to control two valves for this large water pipe. A control signal line comes to the indicator box (red ball) that shows the current position of the valve. The signal line out of another indicator box of the top actuator (hidden from view) can be seen to connect to the solenoid value (small black box attached to the back of the top actuator) which is used as the pilot for the actuator. The solenoid valve controls the air pressure coming from the input air line (small green tube). The output air from the solenoid valve is fed to the actuator's chamber, increasing the pressure . The pressure in the actuator's chamber pushes the pistons away. While the pistons are moving apart from each other, the attached racks are also moved along the pistons in the opposite directions. The racks are connected to a pinion at the direct opposite teeth of the pinion. When the two racks move, the pinion is turned, causing the attached main valve of the water pipe to turn.