ABB 6128/28-84-500 constant room-temperature controller for fan-coil convectors in 2-pipe and 4-pipe systems and conventional heating or cooling installations. Includes a labelling field and rocker switch left/right (switching, dimming, blind, value sender, light scenes, fan function) with master/slave configuration and base-load operation. Fan stage is switchable manually or in automatic mode. Communicates over the KNX (TP) bus with the 6120/12-101 or 6120/13 bus coupler; flush-mounted, IP20, temperature class I with 1.0 percent contribution to space-heating energy efficiency.