to cover this gap the central processing unit 21 judges that output of the stop signal s2 from the control circuit 2 should be delayed for a period corresponding to 30 degrees crank angle interval on the basis of this judgement the central processing unit 21 carries out deduction of 30 degrees from the initial stop lag angle 250 degrees and fixes the result of this reduction 220 degrees as 34 the secondary stop lag angle 34 which is then passed to the memory 22 for storage in this case the initial stop lag angle in the memory 22 may be replaced by the secondary stop lag angle when required after the case of the first trouble on the loom has been removed the loom restarts its rotation it is assumed that the second trouble occurs in this reiterate rotation then the central processing unit 21 calculates the difference between the stop crank angle 310 degrees represented by the stop position signal s1 and the secondary stop lag angle 220 degrees newly stored at the memory 22 thus the difference is found to be equal to 90 degrees as a consequence the control signal generates a stop signal s2 the moment the current crank angle becomes equal to 90 degrees in the manner described above the actual stop angle of the loom is compared with the selected stop crank angle at the setter 1 and at every stop of.