KNX - A Standardised Communication System
In order to implement different functions within a building, a modern building comprises a multitude of:
- sensors (for instance brightness, motion and push-button sensors)
- actuators (for instance relay, dimmer, motor),
- control devices (for instance HVAC installations)
- control and monitoring devices (visualisation devices).
In order to enable the interaction between these different devices, they must communicate with each other. In conventional building technology systems, heating, ventilation and air conditioning (HVAC) installations are passed separately, causing a great wiring effort. An interconnection of the devices is technically very complex and often impossible. This problem can be solved by using the building system technology with KNX.
The European Installation Bus KNX is an industrial communication system used in the building technology system for the interconnection of technical devices. It is the only open protocol standard for home and building system technology in the world. "Open" means in this context that the KNX communications protocol is disclosed so that different manufacturers may use it as a basis for the development of their devices. Thus, different devices can communicate with each other via KNX. The fact that devices by different manufacturers are able to exchange data and information is called interoperability.
The data to be exchanged are transmitted digitally via the installation bus in the form of telegrams containing a series of bits. Different transmisssion media can be used for the bus: twisted pair cable (KNX.TP), power line (KNX.PL), radio frequency (KNX.RF) or fiber-optic cable. The KNX bus can be installed in residential as well as functional buildings. It can be subsequently integrated into old buildings, as well.
KNX is used for example to implement lighting, shutter and blind control functions. It enables the creation of a functional network by connecting all the systems (heating, ventilation, lighting, etc.) in a building. A sensor, for instance a push-button sensor, generates a command and sends it via the bus as a data telegram to an actuator. The actuator, in turn, confirms the reception by sending an acknowledgement telegram and implements the command, for instance by switching a relay.
An important tool when using KNX is ETS (Engineering Tool Software), a configuration tool software released by the KNX Association. ETS helps to design and configure intelligent home and building control installations with the KNX system.