Air Bag Systems: Description and Operation

Description
The SRS is a safety device which, when used in conjunction with the seat belt, is designed to help protect the driver and front passenger in a frontal impact exceeding a certain set limit. The system consists of the SRS unit (including safing sensor and impact sensor), the cable reel and driver's airbag, and front passenger's airbag.

Operation
The main circuit in the SRS unit senses and judges the force of impact and, if necessary, ignites the inflator charges. If battery voltage is too low or power is disconnected due to the impact, the back-up power circuit will keep voltage at a constant level.


For the SRS to operate:
1. The impact sensor and safing sensor must activate, and the impact sensor must send an electric signal to the evaluation circuit.
2. The evaluation circuit must compute the signal, and must send a signal to the ignition drive circuit.
3. The ignition drive circuit must ignite the inflator charges which deploy the airbags.