SMC Corporation of America
Elite Part Number Search
Search Results "AMS40A-N04C-EN-KLE"

(Refer to the FAQ about switching failure, which can be found here.)
For normally closed use: Plug the B port and pipe to the A port.
For normally open use: Plug the A port and pipe to the B port.
Note) Do not plug the exhaust ports (EA or EB); instead, mount a silencer.