main function: ◎Enter into? the rear sensor work, the front turned off ◎The rear sensors detecting distance:0.3?1.5M ◎VFD display digital distance and right-and ?left obstacle ◎4 sensors design, all direction no spot. ◎Sound alarming, mute alterative ◎Sound alarm gradually ◎Sensor with a precision of 0.1M ◎Ultrasonic wave detection