The tekmarNet (R) Thermostat 557 is a communicating touchscreen thermostat designed to operate either: a hydronic radiant floor with a two stage heat pump (water-to-air or air-to-air) for heating & cooling and an emergency backup heating system; or two stages of heating and two stages of cooling. There are three auxiliary sensor inputs that can be used to measure room, floor, outdoor or duct temperature. The optional floor sensor allows precise heating of radiant floors. Relative humidity level can be measured and controlled using either the built-in or external humidity sensor. The large touchscreen display allows you to easily adjust 7-day programmable schedules and room temperatures to optimize comfort and energy savings. The 557 can connect to tekmarNet (R) controls using two or four wires or it can operate as a stand-alone device.