The Bird-X Balcony Guard Silent Bird Repeller is an ultrasonic bird repeller that keeps pigeons and other bird pests away from balconies, decks, terraces and other places where birds create a mess. A humane, effective and maintenance-free solution. Ultrasonic bird repeller Keeps pigeons and other bird pests away from balconies, decks and terraces Humane, effective and maintenance-free solution to eliminate bird droppings No messy, expensive chemicals Covers up to 900 sq. ft. Continuous or motion-sensor operation Motion sensor range: 35ft. x 70ft. Adjustable frequency of sonic or ultrasonic sound (15,000–24,000 Hz) Weatherproof Blends with any decor Powered by included 50-ft. cord with AC adapter or 4 C batteries (not included) Costs less than 25 cents a month to operate (AC) Wall mountable