Car Parktronic Automatic LED Parking Sensor with 4 Sensors Reverse Backup Parking Radar Monitor Detector System Display UniversalFeatures: 4 Sensor system, double CPU and advanced chipset for enhanced coverage and detection. With digital colored LED display (number & light). Help to prevent dangerous and costly collisions. Help to provide increased safety for paengers, pedestrians and family members who happen to be around the moving vehicle. Detect small children and low walls. Anti-freeze and rain proof. Easy to install. Specification: Detection Distance: 0.3m~2.5m Alarm Distance: 0.3m~1.5m Working Frequency: 40KHz Working Voltage: 12V DC Current Consumption: 20ma-200ma Working Temperature: -30~70 Alarm Volume: 70~85dB Maximum Power: 2w Hole Size: 22~22.5mm Note: The maximum effective range of reversing radar detection is 2.5 meters. The sound reflection intensity of different obstacles is different, and the detection distance will vary. To All Buyers If you have any problems when you get parcel,please feel free to contact me,we'll be only too glad to aist you,have a good day. 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 recees. 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 mo.