Wireless Door Chime, Entry Alert, Visitor/Customer Entrance Alarm with 16 Selectable Melodies 16 selectable melodies; Includes simple Ding Dong chime; Wireless entrance alert; Adjustable angle Easy installation; Attractive, compact design; Sounds when the door is opened or visitors pass the device; Portable or wall mount No wiring needed, great for travel; Fixed loudness; Never miss a visitor or delivery again; Great for shops, offices, homes May be used to monitor children or the elderly; Wall mount bracket included; Easy to remove from wall mount, great flexibility Operates on 3x AA batteries (not included); Size: 3.9" H x 2.6" W x 1.4" D (100mm x 65mm x 36mm)