XDV Pneumatic valves play an important role in a pneumatic system. They determine how much air passes through and in which direction. This means that they can be used as control valves, but also as safety valves that shut off the air supply in dangerous situations or that depressurise the system. Every valve basically consists of three elements: Typically 2, 3 or 5 connections which are also called ports. The minimum of two ports provides power to the valve and work. A third port is used for exhausting the valve or actuator if necessary. If five ports are available, this is usually to control a double-acting cylinder. One port remains available for supply, two ports are used for working and two for exhausting. A port is nothing more than an opening with a thread into which a coupling can be inserted. Often a push-in coupling with which a direct hose connection can be made.