Any one of ECUs that are operating detects a present power supply voltage repeatedly. The wrench has four generally square apertures of varying sizes, descending from a relatively large aperture to a relatively small aperture. A first dual acting fluid operated cylinder is slidably positioned on the first leg of the L-shaped bracket. The rule compliance checking of the present invention allows users to perform fast and effective automatic checking of rule compliance, avoid interference of man-made factors in checking process to a great extent and thus guarantee veracity of checking results. The neutron counter has a largely reduced size, simplified structure and resultant decreased failure rate as compared to a conventional counter with a large volume. The duct includes retaining structure configured to retain the anchoring element within the duct.