KNX is a European standard used in home automation. It's primarily based around a twisted pair bus transporting DC power (30V) and data at 9600 bits/second. Devices attached to this KNX bus draw power for their operation and receive and send messages called telegrams. The devices are typically things like switches, relays, dimmers, HVAC interfaces, small displays, and blind/shutter controllers.| John Graham-Cumming's blog