The new SL-650QN includes even more features to protect against false and missed alarms caused by misalignment and environmental issues. With 650' of outdoor detection range, the QN model is perfect for mid-level security perimeter applications. New features include Quad beam which radically cuts down on false alarms caused by birds and falling leaves; Sniper ViewFinder and alignment dial - The new telescope lens on the SL Series has a high level of visibility for optical alignment work. Even at 650', a perfect installation and stable performance can be achieved in minimal time. BAU-4 Compatible - The BAU-4 beam alignment unit automatically and accurately adjusts the optical access. This allows peak performance and gives one technician the ability to align a 200' to 650' SL detector without additional help.