Invisi beam Field Disturbance Sensor</br>Generates two invisible detection fields around your vehicle</br>Offers either a Warn Away response or full alarm</br>Great for convertibles?? trucks or any car</br>Detects moving high-density objects using RF field-disturbance technology</br>Ideal for convertibles</br></br>Product Description</br></br>Protect your vehicle with an invisible sensing field which detects moving high-density objects (including people) near your car using Radio Frequency (RF) field disturbance technology. Ideal for convertibles?? or any application where zone-intrusion protection is desired. Violation of the outer field can provoke siren chirps (or a WarnAway message from an optional voice module) while intrusion into the inner zone will trigger the system??s siren.</br><br/>http://www.amazon.com/gp/product/B0009VFOME