Abstract: An illuminable unit includes a light tube having a spiral-shaped light body containing a mercury source therein and two end portions downwardly extended from the light body, a cathode terminal supported at the end portion of said light tube. A conductor enclosure, which has a length approximately equal to a length of the end portion of the light tube, has an upper head portion sealedly mounted within the respective end portion of the light tube in a concealed manner so as to substantially reduce an overall height of the illuminable unit. A conductor wire is electrically extended from the cathode terminal through the conductor enclosure to an exterior of the light tube for electrifying said mercury source while electrical connection.

Abstract: The invention relates to a method for calibrating the initial sensitivity of the eddy current roll-flaw detecting apparatus and an eddy current roll-flaw detecting apparatus which can be calibrated by the method. The method comprises the following steps: a) detecting an artificial defect sample to obtain a first vector; b) generating an analogue artificial defect signal; c) adjusting the analogue artificial defect signal to make it equal the first vector; and d) inputting the analogue artificial defect signal into the eddy current roll-flaw detecting apparatus, and adjusting the eddy current roll-flaw detecting apparatus to enable it to give a warning, wherein steps a) and c) are both implemented by means of the impedance analyzing unit having the function of displaying the impedance vector built in the eddy current roll-flaw detecting apparatus.