An apparatus for calibrating a probe station includes a disk having a flat bottom surface, a plurality of thermosensors for measuring a temperature of a wafer chuck of the probe station, the plurality of thermosensors being disposed at predetermined positions on a top surface of the disk, and a level disposed at a predetermined position on the top surface of the disk. According to the present invention, because a level shift of a signal is performed before it is input to the output circuit, there occurs no skew in output data. The position error signal output module outputs a position error signal based on a difference between a head position of the magnetic head over the magnetic disk and a target position on the magnetic disk. In another application, the bus-to-bus dimensions are significantly larger, but power concentration is provided by a pattern of isolation lines that narrow the dimensions of current flow through a zone in which heating is desired.