Security Inspection: Prevent taking contraband, such as: knife, gun and so on. Factory: Prevent the loss of valued objects. Education area: Prevent taking cheat-tool, such as telephone, earphone, electronic dictionary, and so on. Features • Digital design, strong anti-interference ability. • Adjustable sensitivity with high, medium and low. • Simple operation, easy to use and convenient. • High sensitivity to all metals. • Two alarm modes of vibration and sound. • Uses AA battery type which is easily available, and can work continuously for more than 70 hours. • Charging, low battery prompt. • Ni-MH Battery and DC charger (Optional)