This Car Parking Sensor System consists of a Classic Digital Display, a control unit and 4 sensors, the control unit gets its power from the reverse light source. The system uses ultrasonic distance measurements to detect distance between the vehicle rear and obstacles. The systems will display the distance in meters and beep with the beeping getting faster as you get closer to the obstacle. How it works: The rear ultrasonic sensors transmit a "narrow beam" signal. When this signal strikes a solid target directly in the path of the host vehicle, it bounce back to the receiver(same sensors as transmitting). The signals are then sent to and processed by microcomputer and shown on the display. Main Feature: Automatically activate when engaging reverse gear. Digital show the distance in division of a metre and 3 LED light indicates the Left/Middle/Right direction of obstacle. Audible warning sound of "BiBi", faster as you get closer to obstacle. Sound switch on/off if you don't want to hear the "BiBi". 2, 3, 4 sensors optional. Any color of sensor is available to suit for your car. Technical Specification: Operating voltage: 12V±2V. Operating current: <160mA. Operating temperature: -40----+80. Detecting range: 0.3m----3.0m.