Siemens Operation
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The SRS control module and SRS warning lamp receive power when the ignition is switched on (KL R). The control module performs a self check and charges the internal capacitor to approximately 35 volts. The capacitor ensures that enough power will be available for airbag activation. If the self check is "OK", the warning lamp goes out and the system is ready for activation should the need arise.
During the instant of activation the capacitor voltage is used to energize the ignition pill of each airbag gas generator. The airbag fills rapidly with a nitrogen gas (N2) supplying the needed margin of safety.