1. Main features:- humidification (heating)dehumidification (cooling) output- switching display of temperature and humidity- highlow limit alarm- sensor calibration- sensor error detection and onoff output control- minimum onoff duration time 2. Models : fx3dh-00: basic modelfx3dh-a1: add on 4 to 20ma transmission outputfx3dh-r4: add on rs485 communication (modbus)