Abstract: A four-mode pneumatic relay includes a relay body defining four chambers, each coupled to a port. Two of the chambers are formed by a diaphragm assembly consisting of a rolling diaphragm coupled to an input post that drives a movable orifice shaft and a pair of diaphragms of different effective areas coupled to said movable orifice shaft. A movable plug assembly includes valve plugs for interconnecting the first chamber with the second chamber and the second chamber with the third chamber via a valve seat and an orifice and recess in the movable orifice shaft. A pair of mechanical switches couple different ones of said ports for providing multi-mode operation. One switch supplies input pressure to either the first port or the third port and another switch couples the second and fourth ports together to vents the fourth port.