http://www.reliablesprinkler.com/pdfs/products/500%20Model%20BX%20Deluge%20Valves.pdf

Here is one type of deluge valve. I wish that we had these in some of our fueling areas. Unfortunately, we have the ones without the external reset knob which require cover removal to reset the flapper. We use solenoid activation from FACPs but you can see that other methods can be used. I'm more used to chasing electrons around so these instructions remind me of the old Mousetrap game.
Joe