Currently selling like crazy on TV under the name "Driveway Alert", this great new 2 piece product will alert you if a car or person passes by the transmitter. Simply place the transmitter near the entrance to your driveway. Anything passing by the transmitter will cause the receiver to sound a pleasant chime. The transmitter can also be placed by your front door to alert you if small children (or big children at night!) try to leave the house. Business owners can be alerted when customers enter the store while working in the back. It installs in seconds. Just place the transmitter outside and the receiver inside. The transmitter can be placed up to 400 feet away from the receiver. The transmitter uses Passive Infra-Red (PIR) to detect motion. The transmitter measures in at 4 1/2 inches x 2 1/2 inches x 2 1/2 inches. The receiver measures in at 4 11/16 inches x 3 1/2 inches x 1 1/2 inches. The receiver requires 3 C batteries or a 4.5 volt adapter (not included). The transmitter requires one 9 volt battery (not included). Covered under a 90 day warranty.