There are many types of button switches, which can be divided into ordinary button type, mushroom head type, self-locking type, self-reset type, knob type, indicator lamp type, light symbol type and key type, and there are single button, double button, I button and different combinations.Generally, it adopts the water-accumulated structure, which is composed of button cap, return spring, static contact, moving contact and shell, etc. It is usually made into a composite type with a pair of normally closed contacts and normally open contacts, and some products can increase the number of contacts through the series connection of multiple elements.There is also a self-sustaining button, which can automatically keep the closed position after being pressed, and can only be opened after the power is cut off.When the button is not pressed, the movable contact is connected with the upper static contact, which is called normally closed contact.At this time, the moving contact is disconnected from the lower static contact, which is called normally open contact: when the button is pressed, the normally closed contact is disconnected and the normally open contact is closed;Release the button and restore the original working state under the action of the return spring.