The improved Wireless Driveway Monitor sends a wireless signal to your home to alert you when an unannounced vehicle enters your driveway. The receiver chimes and the ALERT light flashes red until reset. The driveway sensor uses a patented magnetometer sensor system. Movement of any large metallic (iron or steel) object close to the driveway sensor will cause the sensor to transmit to the receiver. People, animals and shadows will not trigger the driveway sensor. The sensor operates up to 1000 feet (line of sight) from the receiver in your home. Additional sensors may be required for driveways exceeding 12 feet or to monitor an additional driveway.