The thermostat is mounted on lower side of one or more resistor elements and has direct thermal contact. The standard switching temperature is 260°C. Other (lower) temperatures are possible.
If the thermostat is connected to the coil of a contactor, it can work as a thermal fuse. The switch is specified to 250/380VAC, 10/5A.
The thermostat is isolated from the resistor via the ceramic housing. For voltages >400VDC the thermostat is
isolated with a double MICA strip