Detection Range: 0cm - 2.5m^Alarm Volume: 80dB^Ultrasonic Frequency: 40KHz</br></br>Product Description</br></br>This sensor system is a complete package that works independently of any other system and comes with everything needed for installation. Its 4 sensors mount on the rear bumper of a vehicle and it comes with a small console that's placed in the front of the vehicle. The console displays the distance you have behind your car and has a speaker which beeps the closer you get to an obstacle behind you.?The audio pulse intensity increases and the audio frequency changes as the vehicle backs closer to the obstacle.</br><br/>http://www.amazon.com/gp/product/B00PJ2Z9YQ