Air cushion actuation and malfunction detection and recording circuit

Abstract

A control circuit for actuating an inflatable air cushion in a motor vehicle includes an electrically operated actuator comprising a plurality of squibs and a plurality of diodes having their anodes connected to one sides of the squibs, respectively. The actuator is connected between first and second normally open vehicle collision responsive switches. A first resistor is connected across the first switch while a second resistor connected across the second switch thereby to normally establish a potential at a first junction between the first switch and actuator, a potential at second junctions between the diodes and the squibs and a potential at a third junction between the actuator and the second switch. A malfunction detection circuitry is provided for monitoring the voltage at the first, second and third junctions and for energizing recorder means in the event of a malfunction in the control circuit resulting in the two voltages at the first and third junctions assuming substantially a relatively low value and substantially a relatively high value, respectively, or in the event of a malfunction in the control circuit resulting in the voltage at the first junction, the voltage at one or more of the second junction and the voltage at the third junction assuming substantially the relatively high value substantially the relatively low value and substantially the relatively low value, respectively.