In the electrical automatic control circuit, it is used to manually issue control signals to control contactors, relays, electromagnetic starters, etc., and the push-button switch only has two states of switch. When multiple states need to be controlled, the knob switch is used. The button switch has an automatic reset, that is, it is turned off when it is turned on, and there is also a self-locking, that is, it is self-locking after turning on, and it is always on. Knob switches are resettable, there are two gears that switch between on and off states, and three gears are generally used for manual, automatic, and stop switching.