A push button is a manually controlled master electrical appliance. It is mainly used to issue operation commands, turn on or off the control circuit, and control the operation of mechanical and electrical equipment. The working principle of the button is very simple. For the normally open contact, the circuit is disconnected before the button is pressed. After the button is pressed, the normally open contact is connected and the circuit is also connected; for the normally closed contact, Before the button is pressed, the contacts are closed, and when the button is pressed, the contacts are opened and the circuit is broken. Due to the needs of the work of the control circuit, a button can also have multiple pairs of contacts that act simultaneously.

Buttons have a wide range of uses, such as starting and stopping of lathes, forward rotation and reverse rotation, etc.; start, stop, rise, fall, forward, backward, left, right, slow or fast operation of tower cranes, etc., all need buttons control.