The pneumatic rotary actuator, Type 2050, consists of a single or double-acting pneumatic linear piston actuator with internal quick-acting screw thread coupling to a turn element and a universal mechanical interface to DIN 3337 and ISO 5211. During the linear movement of the piston under the pressure of the control air or the force of the return spring, the actuator shaft is turned through 90° by the quick-acting screw thread coupling. This rotary movement can be used to operate corresponding armatures such as ball valves, flap valves, etc. The actuator has an optical display for the piston position.