Abstract: The apparatus monitors lap formation at a pair of rolls guiding a slubbing or sliver in a drafting arrangement for spinning machines. In the event of a lap or coil forming, for example, on a pressure roll, a piston rod of a piston is shifted away until a switching element touches a contact edge or region of a switching sleeve. A cylinder housing encircling the switching sleeve and otherwise electrically separated from the piston is thus short-circuited with the piston. Since the switching sleeve and piston are separately connected to a control unit, a switching function is effected in the control unit by this short-circuit and the drafting arrangement is thereby stopped. The switching sleeve is slidably guided on a guide rod mounted at an upper part in such a manner that the frictional resistance is greater than the weight of the switching sleeve.