Enhanced method for embedding watermarks based on integer-to-integer wavelet transform is provided. At least one of the first insulator layer 13 and the second insulator layer 15 contains as a main component barium titanate and as subordinate components magnesium oxide, manganese oxide, yttrium oxide, at least one oxide selected from barium oxide and calcium oxide and silicon oxide. The process of manufacture comprises the steps of sintering the lanthanum oxide concentrate, then washing the resultant media. A plurality of signal cables are respectively disposed into the compartments, so that the signal cables are able to be disposed in the electronic slots through the housing and that the signal cables are electronically connected to the corresponding pins respectively.