The thermistor relay is used as a protective relay for motors against thermal overload (unacceptable heating). This heating can occur due to mechanical overload on the shaft or when the motor is operated with unacceptable voltages. A PTC thermistor is used as a sensor, which is placed on the part of the motor that heats up the most when overloaded (e.g. integrated in the motor winding). The device can also be used with motors that have an integrated thermal switch. Integrated error memory with front-side reset button, or connection of an external reset button (terminals B1 - B2). Variant:, 230 V AC, 1 changeover contact