Use to monitor the mailbox, garage, driveway or countless other places. Battery operation and 400 foot range means no wiring is necessary. When a vehicle or person passes the sensor, the receiver emits a pleasant chiming sound. Features include: Completely wireless infrared alert system Place the sensor anywhere on your property and the receiver anywhere in your house up to 400 feet away Receiver makes a pleasant chiming sound when sensor is crossed Receiver uses 3 C batteries and transmitter uses 1 9V battery (not included) Includes retail packaging