Safety Technology International, Inc. STI-3360 Wireless Entry Alert Chime with Receiver – This wireless entrance alert, is an easy to install device. It is capable of notifying you when a protected door or window is opened. When a monitored door is opened, the Entrance Alert sends a signal to the remote receiver, announcing an entrance with music. It greets visitors, customers or clients with the sound of music and alerts of their presence. Operates up to 500 feet (line of sight). Simply mount the small transmitter and magnet to any door and plug the remote receiver unit into any electrical outlet in range. No Wiring required. Offers 10 selectable chimes. Also includes 1 AAA battery. A supervised low battery voice alert will let you know when it is time to change the battery. UL/cUL Listed - FCC certified. STI "We protect the things that protect you."