ABOUT PARKING SENSOR Parking sensors are proximity sensors for road vehicles designed to alert the driver of obstacles while parking. These systems use either electromagnetic ultrasonic sensors. These systems feature ultrasonic proximity detectors to measure the distances to nearby objects via sensors located in the front and/or rear bumper fascias or visually minimized within adjacent grills or recesses. The sensors emit acoustic pulses, with a control unit measuring the return interval of each reflected signal and calculating object distances. The system in turns warns the driver with acoustic tones, the frequency indicating object distance, with faster tones indicating closer proximity and a continuous tone indicating a minimal pre-defined distance. Rear sensors may be activated when reverse gear is selected and deactivated as soon as any other gear is selected. As an ultrasonic systems relies on the reflection of sound waves, the system may not detect flat objects or object insufficiently large to reflect sound - e.g., a narrow pole or a longitudinal object pointed directly at the vehicle or near an object. Objects with flat surfaces angled from the vertical may deflect return sound waves away from the sensors, hindering detection. Also soft object with strong sound absorption may have weaker detection, e.g. wool or moss. FEATURESBrand: CarPro Condition: 100% Brand New Detecting Distance: 0.3~2.5mAlarm Distance: 0.3~1.5 Alarm Voice: >80dB at 10cm Supply voltage:10.5V-15V(12V nominal) Current consumption:200 mA max Working temperature:20C-65CStorage temperature:35C-85C The Diameter length : 22 mm