In Automatic Mode the GFX3 will adjust the humidity in your home based on the outdoor temperature,lowering the humidity in cold weather to reduce condensation. The GFX3 can operate in Manual Mode to control humidity to a specific relative Humidity. In most homes, Automatic operation is preferred to reduce condensation on windows and within the structure. Manual mode is necessary where the outdoor temperature sensor cannot be installed. Manual mode may be desirable where valuable artwork, instruments or woodwork demand constant humidity. The LCD Display is back lit and easy to read. Operation and Installation are simple. The GFX3 can be mounted on an interior wall or on the return duct of the HVAC System.