What is KNX
KNX is an open standard for building automation. Instead of a separate controller for every trade, the devices in the building share one bus and speak the same language, so a switch, a thermostat, a blind actuator and a dimmer are all addressable parts of the same installation.
There is no single brain that everything depends on. Intelligence is distributed across the devices, which is why a KNX installation keeps working when one part of it is replaced, and why it can be extended years after the building was finished.