Air Bag Systems: Description and Operation

The main parts of the air bag system are the deployment loop and the diagnostic energy reserve module (DERM). The function of the deployment loop is to supply current through the inflator module in the steering wheel, which will cause deployment of the air bag in the event of a frontal collision.
The arming sensor, air bag coil assembly, inflator module and discriminating sensors make up the deployment loop. The arming sensor switches power to the inflator module on the power side of the deployment loop. The inflator module is only supplied with sufficient current to deploy when the arming sensor and at least one of the two discriminating sensors are closed simultaneously.