Exploded line diagram of an SRS airbag impact sensor and its com…

Impact Sensor (typical)

The "sensing mass" is a large ball bearing (BB). If there's an impact strong enough to knock it loose from the magnet, it rolls forward and shorts across the contacts. Then the contacts immediately spring it back to the magnet. So it resets as fast as it triggers, every time.

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Owner caption October 2010 · Photo 3572 of 5000