Abstract: There is provided a collision predicting operation system comprising a radar circuit whereby a reflected wave which has been radiated from an oscillator and encountered and reflected from a target is received and caused to interfere with the radiated wave to generate a doppler signal, an oscillator circuit group for generating a periodic wave synchronized with the doppler signal when the amplitude of the doppler signal is higher than a predetermined value and its frequency is within a predetermined range, means for changing the oscillation frequency of the oscillator in synchronization with the periodic wave, and means for detecting the polarity and the amount of change of the phase of the doppler signal changed by the frequency modulating means.

Abstract: A recording system for a vehicle occupant protecting apparatus wherein operating conditions of the various components of the occupant protecting apparatus are recorded, when the occupant protecting apparatus such as an air bag properly comes into operation, when conditions are detected which require the operation of the occupant protecting apparatus although its actual operation does not take place or when any fault occurs in the occupant protecting apparatus, thereby to know the various conditions and circumstances which existed during the collision or under the fault condition.