Description Firing key Mk XVI, Mod 9. Brass with a neoprene rubber sheathed electrical cable and a wound steel wire strain relief. The trigger activates a snap-action momentary electrical switch to complete the firing circuit. Mounted on a wooden plaque. A similar type of key could be used for the salvo signal circuit. In a 16 inch main battery turret, several positions would have to act together to close the firing circuit when the turret is under local control.