to a controllable electric motor 144 controlling the second winder 14 also the facility 15 has by way of lines 44 45 and 46 a connection to detectors 41 42 and 43 on the taking or receiving side of the loom opposite the side at which the jet 36 is located the detectors 41 43 which detect the position of weft yarn end or tip 22 will hereinafter be referred to as picking detectors 4 initially the facility 15 will be set to drive the winder 14 for a time and at a rate to provide the weft yarn length which is theoretically required for a pick however this may be a little too short and the weft yarn may only just reach the first detector 41 to form a proper selvedge on the catching side of the loom on the right in fig1 such a position of the weft yarn tip would not be optimal because of this position of the tip 22 the facility 15 would automatically cause a slight adjustment in the operation of the motor 144 so that in the immediately ensuing or one of the subsequent unwinding operations more yarn would be removed from supply 21 and correspondingly the tip 22 would reach the.