Thyristor is called Double thyristor, as long as the positive voltage is applied between anode a and cathode K, and a positive trigger voltage is input between its control pole g and cathode K. After it is turned on, even if the trigger voltage is removed, it still remains on. So we call it "hair on the trigger.". Another feature is that the conduction angle is controlled, and the amount of conduction also changes. For example, if we turn down the faucet, the water flow will be small, and if we turn up the faucet, the water flow will be large.

Thyristor is widely used: rectifier, inverter, frequency conversion, voltage regulation, contactless switch, etc. Thyristor devices are widely used in dimming lamps, adjustable speed fans, air conditioners, televisions, refrigerators, washing machines, cameras, combined audio, acousto-optic circuits, timing controllers, toy devices, radio remote controls, cameras and industrial controls of household appliances.