impermissible deviations in the yarn number is prevented it is further feasible to apply the output signal of the comparator 26 generated in the above described manner to an evaluating device which determines the uniformity of the yarn the apparatus according to the invention makes it possible to monitor by means of a single measured value transmitter the entire yarn production in the manner described above so that defects in the spinning process are immediately noticed the apparatus according to the invention thus makes possible a monitoring of the yarn production regarding yarn breakage and yarn number oscillations so that conventional and only randomly performed laboratory measurements or quality control can be automatically eliminated and thus an evaluation of the entire yarn manufacturing process is feasible an alteration of the current consumption of the motor which drives the spinning rotor occurs however not only in case of defects in the spinning process but also in case of changes in the conditions of the bearings or the drive thus for example damages to the bearings lead to increased frictional forces and thus to an increase in the current consumption if such a current consumption exceeds a predetermined value the spinning stations are stopped and a warning signal is emitted mechanical components of the spinning device are thus in this manner protected from major damage so that in addition to a quality control of the yarn there is achieved an overall monitoring system for the machinery as mentioned above a multiplex operation of a monitoring device is possible in this connection reference is.