GLASS CRACK DETECTION DEVICE

PROBLEM TO BE SOLVED: To provide a plurality of glass crack detection devices at low cost. SOLUTION: In the glass crack detection devices, ultrasonic reception circuits 23, 27, etc. of each window of a vehicle and ultrasonic transmission circuits 26, 30, etc. of adjacent windows are connected to each other in a loop. An abnormality detection circuit 24 is connected to an ultrasonic transmission circuit 22 at the starting point of the loop and an ultrasonic reception circuit 40 at the terminating point of the loop, and discriminates presence/absence of any abnormality according to whether or not the time difference between the time from the ON-period of the ultrasonic signal to the next ON-period at the starting point and the time from the ON-period of the ultrasonic signal to the next ON-period at the terminating point exceeds the reference value. COPYRIGHT: (C)2010,JPO&INPIT