Apparatus and method for detecting a change in operating state of a power tool and vacuum cleaner

The invention relates to a device for detecting a change in operating state of an electric tool. According to the invention, is to provide such a versatile usable device proposed that the device is characterized by a transmission device with at least one sensor element, an output coupled with this probe member, and an output coupled to the probe member transmitting member and by a receiving device having a receiving member and a coupled thereto, switching element, wherein a linked with the operating state of the power tool measured quantity detected and a sensor signal is connected to the at least one sensor element providable, based on the sensor signal a change in operating state is determined by the probe member and the receiving member is a state change information is contactlessly transmittable by the transmission member in the presence of a change in operating state, and wherein the switching element in the present state change information is operable. Moreover, the invention relates to a method and a vacuum cleaner.