The basic principle of break type is shown here. The ferrite magnet is used as a source of magnetic flux. Thermorite® is used as a resistor of the magnetic circuit to control the amount of magnetic flux that is sent to the reed switch for it to switch on and off. The on and off temperature can be set by choosing different Curie temperatures. The operating mode has two types: off type (also called break) and on type (also called make).