Abstract: An apparatus for detecting collision of a vehicle for an air-bag system, the apparatus comprising means for operating said air-bag system when the signal from a generating means corresponding to a shock to the vehicle exceeds a predetermined value. A switch means manually subjects said operating means to unoperated state for a predetermined period. Whereby an erroneous operation of an air bag system is prevented by the switch means even when a shock is applied to the apparatus for detecting a collision of vehicles while it is being inspected or repaired.

Abstract: A fault diagnosis apparatus for diagnosing a control circuit comprising a squib that activates an air bag or the like, a first and a second switching element for activating the squib, and a collision judging circuit that turns on the first and the second switching elements upon detecting an impact in excess of a predetermined level. A microcomputer included in the apparatus generates a signal that turns on either of the two switching elements. The voltage between the activated switching element and the squib is then detected and compared by the microcomputer with the voltage in normal operation for fault diagnosis.

Abstract: Acceleration speed sensor (3) and trigger means (4) for separating air-bag includes a Wheatstone bridge with reference resistors, (7A, 8A), whereby when trouble occurs, the balance of Wheatstone bridge is lost and current flows to current transformer (12), wherein D.C. noise component is isolated by the current transformer (12) and A.C. noise component is attenuated by phase detection by using reference pulse signals (V.sub.0).