44 may also be provided which automatically delivers from the voltages delivered by the tachometer generators 154 and 155 an actual value which independently of the delivery r p m always corresponds with the draft ratio this value is passed on to the amplifier 42 as the foregoing description shows in accordance with the invention the deviation of the sliver thickness from the desired thickness is determined in the form of analogue electrical quantities normally in the form of voltage values these values before storage are converted into binary values and inserted as binary values in a stepping storage since the essential thing is only which bits are operated in this case but not which value is to be stored in each bit electrical losses which possibly occur play no part the binary values released again after a time corresponding with the time of conveyance of the scanned point in the sliver 1 up to and into the draft zone 100 are converted back into analogue values which are unaltered as compared with the corresponding electrical quantities before storage these electrical quantities are then fed to the control device formed for example as an adjusting magnet 153 which then performs an accurate regulation of the draft through the accurate reproduction of the electrical voltages satisfactory regulation of the sliver thickness is achieved which by adjustment of the frequency of the impulse generator 40 or by alteration of the number of stages in the digital.