Control Description The 512 is a microprocessor-based thermostat intended for either two stage heating or heat-cool applications. The 512 allows for up to two auxiliary sensors. The auxiliary sensors can be used to measure air temperature to get an average temperature for large areas. The auxiliary sensors can be used to measure slab temperature in order to limit the minimum and / or maximum allowed slab temperature. Or the auxiliary sensors can be used to display the outdoor temperature and / or a remote temperature.