Automotive electronic vacuum pump: mainly used in automotive brake system,it can achieve energy saving and emission reduction on demand, and improve driving safety, with maintenance-free characteristics, can be installed independently of the engine at any position. Snap action switch: It has the characteristics of double sets of contacts, forced contact disconnection, contact self-cleaning, magnetic steel arc extinguishing, etc. The contact switching time is basically not affected by the external drive, and is widely used in rail transportation as auxiliary control switches.