Abstract: The task of the invention comprises reliably acquiring documents from an output device with variable output speed without impermissible tractive forces being exerted onto the documents. For this purpose the rotational speed of the transport system of the acquisition unit is determined under no-load condition and the torque of the drive is reduced, for example by current imitation, until the transport rate of the acquisition unit is just above the maximum occurring transport rate of the output device. The torque value thus determined, which represents the torque requirement for overcoming the friction of the system, is stored and set as the nominal value during the document acquisition. As a drive motor can be used DC current motors as well as also load-controlled electronically commutated motors.

Abstract: Bipolarity current-activated windings of powerful stepping motors for high step frequencies are to be indexed such that for each load condition the optimum motor torque is attained. The circuit configuration according to the invention comprises for this purpose chopped power output stages ((1, 2)) which are each activated by direction-dependent logic phase signals (PH12, PH34) of a signal generator (3) for the current feed into the motor windings of the stepping motor drive. Via a chopper pulse weighting circuit (4.2) winding indexing signals are supplied to the signal generator (3). To the chopper pulse weighting circuit (1,2) are supplied logic chopper signals (CH12, CH34) which can be tapped at the power output stages ((1, 2)) at the output side, and a device (7,14) connected to the chopper pulse weighting circuit (4.2) ensures that always only that chopper signal (CH12 CH34) is conducted to the chopper pulse weighting circuit (4.2), which is decisive for the next winding switch-over.