Push button switch refers to a switch that uses a button to push the transmission mechanism, presses or disconnects the moving contact and the static contact, and realizes the circuit switching. It is a kind of electrical appliances with simple structure, composed of a metal shell and a circuit, in the electrical automatic control circuit, it is used to manually send out control signals to control contactors, relays, electromagnetic starters, etc. The working principle of the button: after the power is turned on, it outputs a high level signal, when the button is pressed, the button outputs a low-level signal in the normal state.