Abstract

A circuit for a actuating a vehicle passenger safety restraint such as an air bag includes pyroelectric sensors, pressure transducers, and ultrasonic acoustic sensors for sensing the presence, weight, and relative position of the passenger within a vehicle, respectively, which information is supplied to a control module controlling operation of the restraint. The control module, which includes processor means, calculates the likely effectiveness of the restraint in preventing or otherwise mitigating injury to the vehicle passenger in the event of subsequent operation of the restraint. A signal lamp is illuminated by the control module in the event that the passenger assumes a position which reduces the calculated likely effectiveness of the restraint below a threshold level therefor, thereby warning the passenger of the heightened risk of injury. Preferably, the control module uses the information generated by the sensors to supplement or otherwise corroborate other information received from inertia-type "crash" sensors or frangible "crush" sensors, thereby ensuring operation of the restraint only in those instances where the passenger is indeed placed as risk. Most preferably, the restraint is capable of providing a variable response, and the control module adjusts the response of the restraint prior to triggering the operation thereof so as to provide maximum protection to the passenger against injury.