Electric control circuit for safety apparatus in automotive vehicles

In an electric control circuit for a safety apparatus of an automotive vehicle, which control circuit comprises a series connection of an electric power source, a plurality of normally open switch means to be closed in the occurrence of a vehicle collision, and electrically operated actuator means for actuating said safety apparatus upon closure of said switch means, said circuit further comprising a resistor connected in parallel with each of said switch means, said resistor having a predetermined resistance value defining an electric current applied to said actuator means through said resistor to normally maintain said actuator means inoperative,

• the improvement comprising:
• means in said series connection for directly joining each resistor and each of said switch means to said actuator means,
• a differential amplifier connected to the opposite ends of said actuator means for directly amplifying a terminal voltage appearing between the opposite ends of said actuator means to generate an amplified voltage therefrom,
• a constant voltage generator connected in series with said power source for generating low and high constant voltages therefrom,
• a first comparator for comparing the amplified voltage of said amplifier with the low constant voltage to generate an output signal therefrom when the amplified voltage becomes lower than the low constant voltage,
• a second comparator for comparing the amplified voltage with the high constant voltage to generate an output signal therefrom when the amplified voltage becomes higher than the high constant voltage, and
• means for informing the malfunction of said control circuit in response to one of the output signals from said first and second comparators.