A printed circuit board includes an electronic element, a signal line, an inputoutput interface, and a varistor. The media or fluid is placed in a flask. It is not necessary to stop any data traffic communication on the network in order to perform this function. In some embodiments, the mask includes a semi-transmission region including a first opening pattern disposed at least partially between adjacent first slits and having a plurality of first openings formed into a desired shape, and a second opening pattern disposed at least partially between adjacent second slits and having a plurality of second opening formed into a desired shape.