A switching device driving apparatus has a driver for controlling, according to an input signal, the onoff states of a pair of field-effect transistors connected in series between a first supply voltage and a second supply voltage lower than the first supply voltage, and a detector for detecting the onoff states of body diodes attached respectively to the field-effect transistors. Heated air is blown upward through a first chamber and downward through a second heat chamber. In one embodiment, the short signal is obtained during a short time interval that is at the approximate middle of a long time interval such that the short and long intervals share a common median time value. The supply meter includes an identification mark, which is also located in the region of a guide system, namely guide rails, and which is arranged relative to the guide system such that it can be read with the image reader without changing its optical system.