dancer 13 moves up and down synchronously with the shedding process the dancer 13 is held by a spring 14 so that the warp threads 11 are always under tension the position of the dancer 13 is detected by a motion pickup 29 and a zero point pickup 31 an analog digital converter 30 is connected to the motion pickup 29 and an impulse former 32 is connected to the zero point pickup 31 the motion pickup 29 may for example be designed in the form of a potentiometer whose pickup is coupled to the dancer on the other hand the zero point pickup 31 may be a switch which is closed at a specific predetermined position of the dancer 13 but otherwise is always open the output signals from the impulse transmitter 27 the impulse former 32 the converter 30 and the impulse former 28 designated is np ts and im respectively are suplied to a computing apparatus 35 which as a further input signal is acted upon by a value u and which generates an output signal which is put through to a digital analog converter 45 the computing apparatus includes a conversion computation 36 a nominal value computation 37 a theoretical actual comparator 38 an actual value correction 39 and a linkage 40 the signal ts and the signal u are supplied to the conversion computation 36 while the signal np and the signal is are conducted to the actual value correction 39 depending on its two input signals the conversion computation 36 generates an output signal tk which acts upon.