A temperature and/or wear sensor for brake or clutch devices is designed as a thermocouple in which the conductors (20, 22) that are electrically insulated from each other are arranged inside a friction lining (14) and can be connected to each other so as to be electrically conductive by means of a rotatably mounted brake element (12), clutch element or the like, with which the friction lining can be engaged in order to brake or to depress the clutch (FIG. 1). The conductors can be coupled to an electric oscillating circuit.