ASCO's 2-Way solenoid valves have one inlet and one outlet, and are used to permit and shut off fluid flow. The two types of operations are Normally Closed (NC) and Normally Open (NO). Two types of constructions apply to 2-way solenoid valves, which are direct acting and internally piloted. With Direct acting constructions, the solenoid is energized, the core directly opens the orifice of a Normally Closed valve or closes the orifice in a Normally Open Valve. The valve will operate at pressures from 0 psi to its rated maximum. Internally piloted constructions use line pressure to assist operation. When the coil is de-energized (on a Normally Closed Valve), the pilot orifice is closed and line pressure is applied to the top of the piston or diaphragm through the bleed orifice, closing the valve.