MICRO SWITCH GK Series switches are key-operated safety interlock rugged metal switches which monitor the positions of gates, guards, or doors. The key is attached to the moving portion of the gate, guard, or door. When the gate is closed, the key is inserted into the GK switch indicating a safe position (gate closed) and the machine process can start. The positive opening normally closed contacts are held closed when the key is inserted into the GK switch. Opening the gate, removes the key from the switch. This action opens the normally closed contacts of the switch and interrupts the machine's control circuit.