Droid, I think we have two different systems. Mine is called "Echomaster" and the beeping is from the little speaker - I'm surprised it doesn't give my daughter a headache! The dealer installed it at my request. I only have two sensors on either side of the license plate. I've seen cars with four; once I saw a van with eight...I think someone must have gotten upset with reversing accidents by their significant other and stuck these at every different angle possible on the bumper!

This link below gives a description

http://www.pepboys.com/parts_supplie...chomaster.html