A pilot actuator for controlling the operation of a control valve. The control valve can be part of a thy-type fire suppression sprinkler system in which the sprinkler piping network is filled with pressurized gas such as, for example, air, nitrogen, or another gas. The pilot actuator is a differential valve that actuates the control valve when the gas pressure in the sprinkler piping network is at or below a value for tripping or actuating the pilot valve to the open position. The actuator assembly defines a neutral chamber that is at an intermediate pressure in comparison to pressures at the inlet port and the measuring port when the pilot actuator is in a stand-by state.