Multiple seal protection, water proof, so that it could be working in rain. It is light weight and convenient to carry with high precision. It is with high intension cable protection spring, which is acceptable for wheels to pass by. The handle is designed into hole which is stronger. The plug of cable is imported with high quality. The connector is designed to coattail type to avoid the disconnected with ramps. The pad is made of super high intension aluminum alloy for aviation. The surface is deal by high quality military project oxidation. It is Wear-corrosion resistance. The signal feedback is with high frequency by unitary design.