Abstract: Disclosed is a trouble warning device for an air-fuel ratio sensor mounted in an internal combustion engine. The trouble warning device comprises a comparator which compares the output voltage level of the air-fuel ratio sensor with a reference voltage whose level is higher than the output voltage level of the normally operating air-fuel ratio sensor and an indicator to give warning of trouble in response to the compared result. By using this trouble warning device, correct detection of trouble and reliable warning of trouble in the air-fuel ratio sensor can be obtained.

Abstract: An improvement of a vehicle collision anticipating method and device using transmitted and reflected frequency-modulated continuous waves is provided. A low frequency wave is produced by mixing a part of transmitted wave and a reflected wave from the object. The low frequency wave and a Doppler signal obtained from the low frequency wave are signal processed so as to generate signals. A predetermined distance range is obtained by multiplying a time which is determined by the distance between the vehicle and object and the velocity of said object with respect to the vehicle obtained from the Doppler signal, by a relative velocity of the object with respect to the vehicle. A collision of the object against the vehicle is anticipated by detecting the object entering the predetermined distance range in front of the vehicle.