Automobile three-point safety belt, the general term is "elbow" "conduit" the main function is to install the gas generator in the elbow. When the collision occurs, the collision sensor around the car transmits the pulse signal to the automobile ECU, the ECU detonates the gas generator to generate thrust, and drives the transmission device to make the belt retractor rotate and recover the belt webbed. Restrain person in car seat to prevent secondary injury.