Light-reactive sensor with sensing distance of up to 15ft. can be used with the door open or closed Chime alerts employees when a visitor enters or exits by a pleasant ding-dong sound. Adjustable volume control. Mounts easily on a wall or door frame. Operates with 4 AA batteries. Batteries are sold separately. Tatco Visitor Bell Chime is one of many Call Bells & Counters available through Office Depot. Made by Tatco.