Add an Extra Wireless Receiver for the Wireless Motion Alert system (sold separately), and you'll be able to receive an audible alert in another room in your home. This unit receives radio signals from the transmitter, which can be located at the base of your driveway up to 600 feet away. The Extra Wireless Receiver can also be used to expand the Wireless Probe Driveway Alert (sold separately). The Extra Wireless Receiver for Wireless Motion Alert plugs into a standard wall outlet and can be placed on a table or mounted on the wall (mounting materials sold separately). When the receiver gets a signal from the transmitter, one of four user-specified tones (Classical, Westminster Chime, Ding Dong, or Whistle) will sound for a few seconds. There is also a volume control, allowing you to set the sound to the desired level. An unlimited number of receivers can be installed. Place them in every room in your home, and you'll always know the instant someone steps onto your property. This receiver will also work with the 3000 Series Wireless IR Motion sensor.