The vacuum fixer includes a hat-shaped pressing plate made of rigid synthetic resin, a disk-type suction plate made of soft synthetic resin and covered with the pressing plate, a screw shaft mounted on the upper end of the center of the suction plate and perforating the center of the pressing plate, and a screw tightening member coupled to a protruding front end of the screw shaft. This digital data is passed to a processing system, and an identifier of the media content derived from the sampled values is returned from that system. These plurality of decoder circuits control the word lines to one of high level, low level, and a floating state, thereby writing data in the memory cells or reading out data from the memory cells.