in full lines in fig2 the two equally great warp tension forces are designated with the reference characters e and f they give rise to the resultant sensing force g directed toward the sensor 23 its amount can for instance be about 20 of the amount of the tension vectors e and f the force g moves the sensing roller 16 counter to the action of the spring 20 downward to the left in fig2 causing the spring 20 to approach the sensor 23 which may be constituted by a standard proximity sensor this causes a signal to be transmitted to the related partial control device 25 the partial control device 25 adjusts an appropriate warp let off speed of the related partial warp beam 3 if the responsiveness of the control device at a sensing force g of about 20 of the warp tension is not sufficient the tensioning beam 14 can be for instance by means of appropriately greater preloading of the torsion bar spring 33 urged into a working or operating region corresponding to the position 14a represented in chain dotted lines in fig2 the warp tension arising at the location d and directed toward the tensioning beam located at the position 14a now corresponds to the vector e 39 there therefore arises a considerably greater sensing force corresponding to the vector g 39 of about 60 of the warp tension.