The e4 Smart Digital Thermostat Model E529 is a member of Honeywell's INNCOM Integrated Room Automation System. Its core is a Direct Digital Control (DDC) processor capable of controlling virtually any fan coil unit, heat pump or packaged terminal air conditioner found in guestrooms. It includes an easy to read illuminated liquid crystal display, an onboard transceiver (RF) and the separate X47 logic board. The E529 is battery powered and therefore ideal for certain installations, especially retrofitted in preexisting properties.