You have the main alarm that wires into your battery, then you get a tilt sensor that you put on (put mine on the top of battery box) that detects if the bike is being tilted or moved. It came with another sensor that detects if someone is within so many feet but ANYTHING sets it off so I rarely use it. How I set it off is by activating it and forgetting that I did then going out and putting the key in or going to move it and it goes off. It'll scare the crap outta ya the first few times