Robust 3/2-way valve, directly controlled by spring resetting. Solenoid valves are used where quick switching from suction to ventilation is required. The valve can additioinally be admissioned with compressed air in order to accelerate the ventilation process (max. 1 bar overpressure - on connection 1). When without current, the valves are open (NO). This guarantees that the vacuum circuit is not ventilated in case of a power failure and that engaged goods do not fall off at once.