The KNX bus system
Manual for the training case KNX
9
4
The KNX bus system
Intelligent bus systems are used to improve the quality of buildings in terms of
operating costs, safety and flexibility.
4.1
How did KNX originate?
was a system developed and marketed by the EIB Association (EIBA). In 1999,
the EIBA, the Batibus Club International (BCI, France) and the European Home
Systems Association (EHSA, Netherlands) joined forces. In this fusion, the new
name KNX was created and the KNX Association was founded with its
headquarters in Brussels.
4.2
What is a KNX system?
A KNX system is a bus system for building control. This means that all devices
use the same transmission method and can exchange data via a common bus
line. This means:
Access to the bus line must be clearly controlled (bus access procedure).
A large share of the transmitted data is not user data (e.g. light on/light
off), but address information (from where does the data come, where is
it directed to?).
Another important feature of the KNX bus system is its decentralised structure.
A central control device is not necessary. The "intelligence" of the system is
distributed across all participants. However, central devices are not excluded. If
required, e.g. for very special applications, central devices might be used as an
option. Each device, or each bus sharing unit, has its own microprocessor. One
major advantage of decentralisation is that if one device fails, the remaining
devices continue to function. Only the applications relating to the failed device
are disturbed.
Apart from system devices (power supply, programming interface, etc.), a
general distinction is made in the KNX system between sensors and actuators.
Sensors are devices which detect events in the building (button actuation,
motion, exceeding/falling below a temperature value, etc.), convert these into
telegrams and then transmit them (data packets). Devices receiving telegrams
and converting the commands they contain into actions are called actuators.
Sensors represent the command transmitters, actuators the command receivers.
