The Mail Arrival Notification System is convenient, secure and fun. The transmitter easily mounts attaches to a standard horizontally-hinged mailbox (open from top to bottom) with supplied adhesive strip. When your mailbox is open a pleasant chime sounds and a red light flashes on the receiver to alert you that mail has arrived. The red indicator light constantly flashes on the received until you reset it. With this instantaneous alert you help prevent identity theft by reducing the time your mail sits in the mailbox. The system will also help guard against mailbox tampering and identity thief. During inclement weather it helps reduce repeated trips to the mailbox. The durable weatherproof sensor provides dependable service for many years. The receiver can be placed on a table, installed on a wall, or moved from room to room. The unit has a range of 150 feet (with no obstructions). The set includes the receiver, transmitter, 2 AA receiver batteries, 1 23A 12V transmitter battery and, double-sided tape.