Pneumatic control valves, also known as directional control valves, are used to regulate and control the flow of air and other inert gases within pneumatic systems. These valves are categorized based on several factors, including the number of inlet and output ports, the type of actuator used (manual, mechanical, electromagnetic, or pneumatic), the valve’s status when deactivated (normally open or normally closed), and the number of flow paths or switching positions. These categorizations help determine the appropriate valve for specific applications and operational requirements.