differentiation step for example a triggered search in combination with the expert knowledge of the computer 17 would have to lead in this case to the result that a maintenance action must be called up the counting of events events h is another signal analysis in fig2 a and 2b for example operational events such as the frequency of actuation of switching devices e g manual or automatic switching on or off of power supply to the draw frame autolevelling draw frame or power peaks in the signal of the actual power value of the booster 12 in excess of a defined value are counted as events the frequency with which a starting key is pressed event h in relation to the time and in connection with the mean value establishment for short length a1 of the fiber sliver can yield the information on whether stoppage of the draw frame has occurred because of a fiber sliver segment which cannot be drawn because of irregularities loops knots etc the search result in this case would be an error message 34 loops in the intake 34 another signal analysis consists in the statistical determination of operational and machine data statistics g this can be the measurement of the time period during which the machine is switched on or a measurement.