Optex BX-80N BoudaryGard Outdoor Perimeter PIR Detector Dual-Side Detection Area of the BX-80N can protect both sides of windows when placed between them Creates an audible sonic alarm as well as triggering alarm systems Easy installation Common causes of false alarms such as RFI and unwanted sunlight can be greatly reduced by patented Double Conductive Shielding 80 foot range (40 feet in each direction)