Abstract: A yarn accumulating and feeding apparatus (1) has a stationary accumulating drum adapted to have a yarn (27) formed into a yarn supply (26) thereon, the magnitude of which is monitored between a minimum and a maximum by means of at least one mechanical probe element (28,28',28",28'",28"") adapted to be displaced by the yarn supply between two positions (I,II) and operatively associated with a switching device located outside of the accumulating drum. The probe element is mounted in the accumulating drum for displacement between one position projecting past the surface of the accumulating drum, and another position extending flush with the accumulating drum surface (15) against the bias of a return force, while a switching device contains a sensor element (20,20',21,21',20",20'") for generating a reaction signal in response to displacement of the probe element but without contacting the probe element.