Seco-Larm E-960-D90Q Twin Photo Beam Detectors with Laser Beam Alignment, 90' Built-in laser beam alignment system speeds accurate, reliable positioning Twin infrared beams provide reliable perimeter security, minimizing false alarms from falling leaves, birds, etc. Lensed optics reinforces beam strength & provides excellent immunity to false alarms due to rain, snow, mist, etc. Weatherproof, sunlight-filtering case for indoor & outdoor use Anti-frost system so that beam functions even in extreme conditions