A semiconductor wafer has a plurality of semiconductor die. In one technique, an electrical pulsed waveform is conveyed between a caudal electrode and spinal cord tissue, thereby evoking action potentials that are orthodromically propagated along dorsal column fibers and evoking action potentials that are antidromically propagated along the DC fibers. Further, external view image representing an external view of the person to be examined is displayed, and marks representing the examined regions are superimposed at the positions of the examined regions in the external view image. The covering comprises a recess for temporarily receiving the second sealing member when the covering is inserted into a hole in the material. The keep-alive circuit is connected to provide first and second bias currents to the source terminals of the pair of cascode transistors.