The GST 2 is a universal limit switch for temperature monitoring. The temperature sensor is powered by a potential-free safety voltage from the GST2, which means that no external power supply unit is needed. Switches with three different temperature ranges are available. GST 2A: -30°C - 0°C / GST 2B: 0°C - 50°C / GST 2C: 50°C - 100°C