OBSTRUCTION DETECTOR AND RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide an obstruction detector and a recording medium capable of reducing an erroneous detection of obstruction. SOLUTION: All reception circuits are connected to a ultrasonic sensor 3 (S 200). All of received information of all the reception circuits (S 210) are collected. Whether it is a time to finish noise monitoring is determined (S 220). Whether there is an input having a value exceeding a threshold is determined (S 230). A transmission frequency is set to a standard frequency (S 240). Whether there is an input in all the reception circuits, having a value exceeding a threshold is determined (S 250). A transmission frequency among frequencies of reception circuits which do not have an input with a higher value than the threshold (S 260) is determined. Whether there are inputs among all the reception circuits continuously having a value exceeding the threshold (S 270) is determined. Frequencies of reception circuits having shortest period during which the value exceeds the threshold is selected and that frequency is set as transmission frequency (S 280). The transmission is stopped (S 290).