Normally closed: when the coil is energized, the pilot valve is open, pilot hole, cavity pressure relief valve on the piston cavity, rely on medium pressure to promote, the solenoid valve opens.

When the coil is de-energized, the pilot valve core by the reset spring, the pilot hole is closed by the piston, valve chamber orifice pressurizing and reset spring thrust, the electromagnetic valve is closed.

Normally open: when the coil is energized, the pilot valve core by the reset spring, the pilot hole is closed by the piston, valve chamber orifice pressurizing and reset spring thrust, the electromagnetic valve is closed.

When the coil is de-energized, the pilot valve core by the reset spring, the pilot hole is opened, the valve cavity pressure relief, pressure to push the piston cavity medium, the solenoid valve opens.