Zigzag running warning system for automotive vehicles

Claim 1

A zigzag running warning system for an automotive vehicle, comprising: a magnetic sensor having an annular core, an excitation coil wound uniformly on said annular core, and a sensing coil wound to traverse said annular core; an oscillator circuit for oscillating at a given frequency; a driver circuit for receiving oscillations from said oscillator circuit and driving said excitation coil in response thereto; an amplifier circuit for amplifying an output signal of said sensing coil which varies in amplitude in response to the superposition of terrestrial magnetism and magnetism produced by said excitation coil whenever it is driven by said driver circuit; a detection circuit for envelope detecting an output signal of said amplifier circuit; a change detecting circuit for generating an electric signal as a signal indicating that the direction of travel of said vehicle is changed in excess of a predetermined value when an output signal of said detection circuit is higher than a predetermined value; an electronic unit responsive to said electric signal from said change detecting circuit to discriminate zigzag running of said vehicle as a condition existing when the direction of the terrestrial magnetism with respect to the direction of travel of said vehicle changes alternately with time, and to generate a warning signal when said zigzag running is discriminated; and warning means responsive to a warning signal from said electronic unit for issuing a warning against said zigzag running condition.