Type 280 is a normally closed or normally open servo-assisted solenoid valve (circuit functions A and B). For circuit function A, the valve is normally closed by spring action assisted by the fluid pressure. When de-energized, a pressure is built up above the servo diaphragm pressing it down to close the valve. When energized, the space above the servo diaphragm is exhausted via the pilot valve, the diaphragm is lifted by the fluid pressure to open the valve. G 1/4, G 3/8, G 1/2 Circuit function B, normally open, provides the opposite function. It is important to note that the media is exhausted to atmosphere via the pilot operator when the valve is deenergised. The solenoid epoxy encapsulation efficiently dissipates the heat generated by the coil.