An image forming apparatus includes temperature sensors that measure temperatures at different locations in the longitudinal direction of a photosensitive drum. Hereby, since the sucking force of the suction unit can be set according to a state of the recording medium. Possible states of buttons are \u201cunselected\u201d, \u201cselected\u201d or \u201cactivated\u201d. The system also includes a signal constructor having at least one input coupled to a corresponding at least one analog-to-digital converter signal output and operable to provide a relatively high resolution digital output signal. The power processing module includes a first power input terminal, a first power output terminal, branch circuit protection circuitry coupled at least indirectly between the first power input terminal and the first power output terminal, and at least one bus bar coupling at least two of the first power input terminal, the first power output terminal, and the branch circuit protection circuitry. The method is integrated in that ferrous sulfate produced by oxidizing iron pyrite serves as a source of ferrous ions in the first contacting step.