are drawn and further advanced by a pair of cooperating withdrawing rollers 4 and 5 in their travel through the sliver guiding device the slivers 3 move past a measuring member 6 the drawing frame 1 includes an upper inlet roller 7 and a lower inlet roller 8 which are associated with the pre drawing zone 9 delimited at the downstream end by the upper predrawing roller 10 and the lower predrawing roller 11 between the roller pair 10 11 as well as a roller pair formed of the upper main drawing roller 13 and the lower main drawing roller 15 the main drawing zone 12 extends the lower main drawing roller 15 is associated with a second upper main drawing roller 14 such an arrangement is referred to as a four over three drawing system the drafted slivers 3 after passing through the roller pair 14 15 reach the inlet of a sliver guide 16 and are drawn through a sliver trumpet 17 arranged at the downstream end of the sliver guide 16 by cooperating delivery rolls 18 18 39 in the sliver trumpet 17 the slivers are combined into a single sliver deposited into a non illustrated coiler can the main drawing rollers 13 14 15 and the delivery rollers 18 18 39 are driven by a main motor 19 controlled by a computer 21 the signals generated by the measuring member 6 at the sliver guiding device 2 are applied to the computer 21 and are converted into control signals which are applied to a regulating motor driving the withdrawing rollers 4 5 as well as the rollers 7 8 10 and 11 of the pre drawing zone 9 according to the signals of the measuring unit 6 representing the fluctuating thickness values of the sliver assembly.