開關

power switch / gas valve / to open the city (or frontier) gate / to open and close / to switch on and off

to open / to start / to turn on / to boil / to write out (a prescription, check, invoice etc) / to operate (a vehicle) / carat (gold) / abbr. for Kelvin, 開爾文|开尔文[Kai1 er3 wen2] / abbr. for 開本|开本[kai1 ben3], book format

mountain pass / to close; to shut; to turn off / to confine; to lock (sb) up; to shut (sb in a room, a bird in a cage etc) / to concern; to involve

main switch

pneumatic switch

ignition switch