A device for effecting the positionally accurate conveyance of flat articles to be sorted to an input device for a sorting conveyor has a draw-off unit and a feed unit. Based on the signal, the voltage command calculation unit determines a target voltage of a voltage step-up converter that corresponds to a terminal-to-terminal voltage of the capacitor. The current sensor provides high measurement accuracy for both DC and AC currents, and is substantially immune to the effects of temperature, conductor position, nearby current carrying conductors and aging. The processor is further configured to indicate to a second database to check the condition using data in the second database, wherein the data is associated with the transaction.