The invention relates to a diamond electrode with synthetically produced, electrically conductive diamonds. The DRAM includes a plurality of sub-arrays, each having a plurality of memory cells, each of which is coupled with a complementary bit line pair and a word line. The processing of the key data comprises the steps of receiving key data, processing the key data, and generating processed key data. In addition, the filing tool has higher strength, due to the use of the metal plate. The adjustment control unit controls the equalizer adjustment unit so as to perform equalizer adjustment of the playback signals according to the playback signals based on reflected light from a management information area on a recording surface of the optical disk, the management information area including predetermined management information recorded thereon.