Coded radio signal works indoors, outdoors, around corners and through walls. Line of sight is not required between Sender and Remote.PRODUCT FEATURES: With 4 "AA" alkaline batteries you receive up to 400 hours power; Up to 800 hours with 4 "AA" Lithium batteries; The Remote can also use AC power with the 515 Adaptor/Charger; Shoe/tripod Mount Adapter; Pole Mount, Instruction Manual.