rpm value the lower output roll i and the calender rolls 8 and 9 are driven by a principal motor 32 the regulating motor 31 and the principal motor 32 have a respective regulator 33 and 34 the rpm regulation is effected by means of a closed regulating circuit in which the regulating motor 31 and the principal motor 32 are provided with a respective tachogenerator 35 and 36 at the drafting unit inlet 24 a mass proportional magnitude for example the sliver cross section of the slivers 2 are measured by the inlet measuring member 28 at the drafting unit outlet 25 the cross section of the exiting sliver 11 is sensed by an outlet measuring organ 37 associated with the sliver trumpet 10 the central computer unit control and regulating device 38 for example a microcomputer with a microprocessor transfers the setting of the desired magnitude for the regulating motor 31 to the regulator 33 the measured magnitudes sensed by the measuring member 28 are applied to the central unit 38 during the drafting process from the measured magnitudes sensed by the measuring member 28 and the desired value for the cross section of the exiting sliver 11 in the central unit 38 the setting magnitude for the regulating motor 31 is determined the measured magnitudes sensed by the outlet measuring organ 37 serve for monitoring the exiting sliver 11 by means of such a regulating system fluctuations in the cross section of the inputted sliver 2 may be compensated for by a suitable regulation of the preliminary drafting process that is an evening of the outputted sliver 11 may be achieved in the system illustrated in fig4 designates an inputting device.