Type 2/977 valves for potentially explosive atmospheres are direct and external medium controlled and require external compressed air 4-10 bar for switching. The design is simple and solid with fast response times. This type of valve can be traversed and shut off from both sides. The ‘medium pressure below valve seat’ option should be selected in order to effectively prevent closing impacts with liquids. Special conditions (X) must be observed: Limitation of the ambient and medium temperature depending on the sealing material used.