Abstract: A circuit for controlling the actuation of a vehicle air bag system includes a two terminal electrically actuated ignition element connectable to a drive voltage line through a first transistor and to a circuit ground through another transistor. The voltage source includes the vehicle battery and a capacitor that is charged by the vehicle battery and which supplies operating power in the event the vehicle battery is removed from the circuit, for example, as a consequence of a collision. The transistors are normally biased to a non-conducting state sufficient to isolate the ignition element from the drive voltage source and circuit ground. Vehicle acceleration is sensed by an acceleration sensor which, in the event of a collision, biases both transistors into conduction to effectively connect the two terminals of the ignition element to the drive voltage line and to ground to actuate the vehicle air bag.

Abstract: A vehicle operator protection system includes an actuating device, a battery for supplying the actuating device with electric power, and a backup capacitor charged by the battery and supplying power to the actuating device when the battery becomes inoperable. It further includes a switch for cutting off the power supply from the battery and a determining circuit for detecting a discharging condition of the backup capacitor after it has been cut off from the power supply with the switch to determine the existence of an abnormality in the backup capacitor and the actuating device. Through the detection of the discharging condition of the backup capacitor, determination of the existence of an abnormality, based on the intended function of the backup capacitor, can be achieved.

Abstract: A releasing circuit for actuating a vehicular safety device includes a sensor arranged to provide an acceleration signal responsive to accelerations of the vehicle and an evaluating circuit for setting a predetermined condition for activating a release element of the safety device and responsive to the acceleration signal for effecting the activation of the release element when the predetermined condition has been satisfied by the acceleration signal.

Abstract: An acceleration sensor detects an acceleration of a vehicle which is caused by a collision of the vehicle. A safety device protects an occupant in the vehicle from the collision of the vehicle. A trigger device triggers the safety device. The trigger device is activated in response to an output signal from the acceleration sensor. An operation of the trigger device is detected and a detection signal representative thereof is generated. A first judgment device judges whether or not the trigger device is activated on the basis of the detection signal. When the trigger device is judged to be activated, a second judgment device judges whether the activation of the trigger device is caused by a correct cause or a false cause on the basis of the output signal from the acceleration sensor. The judgment by the second judgment device is allowed only once and subsequent judgments by the second judgment device are inhibited. A result of the judgment by the second judgment device is recorded.