When compressed air enters the pneumatic actuator from nozzle A, the gas pushes the double piston to move linearly towards both ends (cylinder head end), and the rack on the piston drives the gear on the rotating shaft to rotate counterclockwise by 90 degrees, and the valve is opened. At this time, the gas at both ends of the pneumatic actuator valve is discharged with the B nozzle.

On the contrary, when compressed air enters the two ends of the pneumatic actuator from nozzle B, the gas pushes the double plug to move in a straight line towards the middle. The rack on the piston drives the gear on the rotating shaft to rotate clockwise by 90 degrees, and the valve is closed. At this point, the gas in the middle of the pneumatic actuator is discharged through nozzle A.

The above is the standard transmission principle. According to user requirements, the pneumatic actuator can be installed with the opposite transmission principle to the standard type, that is, clockwise rotation of the selected shaft opens the valve, and counterclockwise rotation closes the valve. The A nozzle of the single acting (spring return type) pneumatic actuator serves as the air inlet, while the B nozzle serves as the exhaust port (the B nozzle should be equipped with a muffler). The intake of nozzle A is to open the valve, and when the gas is cut off, the valve is closed by the spring force.