KNX
European standard for building automation — lighting, blinds, heating, AC. Replaced EIB, BatiBUS, EHS in 1999.
ISO/IEC 14543-3. Twisted-pair (TP1) is most common — a 29 V DC bus provides both power and communication. KNX Powerline (the old electric grid), KNX RF (radio), KNX IP (Ethernet). 500+ vendors in the KNX Association. ETS (Engineering Tool Software, Windows-only, expensive) is required for configuration. Most common in newer European buildings; competitor in the US: BACnet, LonWorks. Home-automation DIY folks more often prefer Zigbee/Z-Wave/Matter — KNX is professional only.