KNX is an open standard for commercial and residential building automation.
The most imporant feature of KNX is its decentralised structure. There is no need for a central control unit, because the “intelligence” of the system is spread across all of its devices.
KNX devices can manage all sorts of things like lighting, blinds and shutters, HVAC and security systems.
Generally in a KNX system, devices fall into three categories: system devices (power supply, programming interface, etc.), sensors (temperature, humdity, etc.), and actuators (convert commands into actions).
Another important part of KNX is the certification. Any product labeled with the KNX trademark must be certified to conform with the standards set by the organisation. This means that even older KNX devices will still work with current technology.
A KNX wired network can be formed with tree, line and star topologies (these can also be mixed together). Ring topologies are not supported.
KNX can link up to 57,375 devices using 16-bit addresses.
Line Couplers units allow address filtering which can help performance, given there is a limit on bus signal speed.
A two-core twisted pair data cable (bus cable) is the most common communication medium for KNX installations.
This cable provides the devices on the bus with data and power. The data transfer rate is 9,600 bit/s, and the data will travel serially, one byte at a time, via asynchronous data transfer.