ALWAYS KNOW WHEN SOMEONE IS APPROACHING. The Wireless Watchdog is your personal security alert that lets you know when a person or vehicle is approaching. Its wireless infrared sensor can be placed anywhere inside or out. When a person or vehicle passes the sensor, the movement will trigger a loud alarm and flashing LED on your receiver. Clip the receiver to your belt or place it on a tabletop next to you. Sensor works up to 400’. Adjustable volume. Uses 3 AA and one 9-volt battery (not included). Receiver 1.4”x3”x4”. Sensor 1.7”x2.9”x4.2”.