to reduce the width of the slot 8 39 of the control plate 10 for removal of the weft at the detecting section 17 but only to a minimum equal to the diameter of the controlled weft thread 9 in order to enable its removal because of the projection of the photocell 14 into the reduced width portion of the slot 8 39 the exiting weft thread 9 will exert a positive wiping action of a frictional nature on each of the elements of the detecting section 17 the detecting section 17 thus remains constantly clean without dust or fibers and consequently does not cause the generation of wrong signals picking combs 2 particularly in looms of larger width may be divided into sections and arranged on the slay 1 of the loom the plates 4 of each section of the picking comb 2 are fixed on a bar 20 for instance by glueing the bars 20 with the plates 4 together with the reed 3 are mounted in a groove 19 of the slay and secured thereto by screws 21 the arrangement for the control of the introduced weft 9 represents advantageously an independent control section of the picking comb 2 see fig3 and 4 fixed on the required control place of the introduced weft by means common to that for fixing the sections of the picking comb 2 and of the reed 3 i e in the groove 19 of the slay and secured thereto by screws 21 the arrangement for the control of the introduced weft 9 represents advantageously an independent control section of the picking comb 2 see fig3 and 4 fixed on the required control place of the introduced weft by means common.