3/2-way valve, monostable • Normally open, normally closed • Mechanical spring • Vacuum operation possible • Directly actuated and pneumatically pilot-operated • Ducted exhaust air 4/2-way valves, monostable • Mechanical spring • Pneumatically pilot operated • Ducted exhaust air 5/2-way valve, monostable Pneumatic spring/mechanical spring • Vacuum operation possible • Reversible in some cases • Pneumatically pilot operated • Ducted exhaust air