Currently selling like crazy on TV under the name "Drive Way Alert", this great 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 the front door to alert you if small children (or big children at night!) try to leave the house. Business owners can place the unit by the front door and be alerted when customers enter the store while working in the back. The drive way alert installs in seconds just place the transmitter outside and the receiver inside. The drive way alert uses wireless technology so the transmitter can be placed up to 150 feet away (line of sight) from the receiver. The transmitter uses Passive Infra-Red (PIR) to detect motion. The transmitter measures 4 1/2 inches x 2 1/2 inches x 2 1/2 inches. The receiver measures 4 11/16 inches x 3 1/2 inches x 1 1/2 inches. The transmitter requires 1 - 9 volt battery that is NOT included. The receiver requires either 3 - C batteries that are NOT included or a 4.5 volt adapter that is NOT included. Simple installation. 150 ft. recommended maximum line-of-sight wireless transmission distance between sensor and receiver (approx. 75' to 125' wireless range through 1 outside wall).