After everything is fully installed, you put in reverse you will hear a beep- to let you know the SmartPark is in operational(that`s the first zone of detection(safety zone).As you start backing up you will hear a continuos beep- second zone of detection.Then when beeping increases in frequency and changes in pitch you are now in the third zone of detection- you should stop. This is only the basic principle. You may adjust the distance of the zone depending on your preference . the beep is so cute too.