again at the instant b the clock or start pulse 10a corresponds to an angular position of the main drive shaft 9 of e g 100 degrees a very accurate adjustment of this angle is possible by a clock pulse generator 10 which comprises an exactly graduated circular scale the adjustable delay circuit 12e makes it possible to delay the sensor signal 11a and thus the instant b of the braking signal 12 by a time interval which is adjustable within certain limits as illustrated by the dashed line thus the instant of actuation of the thread brake 3 may be accommodated to various operational conditions of the weaving machine thus avoiding any mechanical adjustment or displacement of the sensor 11 the time delay circuit 12e may be lodged in a portable housing or case provided with a plug connection or connector thus it is possible for an operator to adjust the instant b and to simultaneously watch the selvedge such a procedure is not possible with the presently known control devices referring to fig3 and 5 an inductive sensor 11s comprising an induction coil is fixed to the lathe beam 6 by means of a coil support 15 and screw 16 or equivalent structure the substantially rectangular shape of the inductive sensor 11s fig5 is accommodated to the cross section of the guide tooth 7 and to the distance to the thereto adjacent guide teeth 7a 7b thus the inductive sensor 11s can be set onto the guide tooth 7 from the top thereof without removing the same from the lathe beam 6.