What is KNX?

The KNX Standard is a preferred world standard for solutions such as lighting in a small residence, to lighting automation at the world's largest airports.

At the end of 2003 the KNX standard CENELEC (European Committee of Electrotechnical Standardization of the Home and Building Electronic Systems of the EN 50090 series approved as part of the standard. Also KNX Standard CEN (EN 13321-1 For the media and the protocol is approved by EN 13321-2 KNXnet / IP). At the end, the KNX is certified as a world standard (ISO / IEC 14543-3-1 to 7). In May 2013 KNX technology was approved as the Chinese standard (GB / T 20965). ANSI / ASHRAE has been approved by the United States as the 135th.

Projects that can be done with KNX

With KNX infrastructure, from a small house to a large airport, lighting, curtain-blinds, air-conditioning, central monitoring and control, safety, time-based controls, daylight-related controls, any manual or autonomous controls such as key control permits can be done. In this context, KNX automation system is used in the following projects;

  • Office / Plaza
  • School / Hospital etc.
  • Shopping Malls
  • Public buildings
  • Industrial Plants
  • Residences

Using appropriate interface devices  (gateways), it is possible to transmit KNX telegrams to different media protocols. For examle;

  • BacNET
  • LonWORKS
  • OPC
  • Modbus

A (twisted-pair) two-wire control cable, which is most commonly parallel to the 230V power cable, is used in the system.

KNX cable;

  • Enables communication between the actuator and sensors (switch, sensor, thermostat etc.)
  • Provides power to the bus line,

Each KNX bus has its own processor (without the need for a central control unit such as a computer). That's why KNX can be used in small applications (apartment, residence) and large applications (hotels, administration buildings, airports).

The KNX information exchange between devices can be made with a separate control cable as described in the previous paragraphs. Besides KNX also offers following communication types;

  • Existing 230 V cable (Powerline transmission medium)
  • Wireless (KNX radio frequency) and Ethernet / WIFI (KNX IP).

Appropriate media supplying devices must be used when connecting different mediaprotocols. Information on its conformity is indicated on the labels of the devices. (This manual is mainly focused on the KNX Twisted Pair / Two-wire communication system.)


Generally, since the cable structure is the same type with fire monitoring systems, it is observed, fire-system cables are also used for KNX.

In this case, the maximum line length allowed may vary. In addition, if the same color is used for both systems, electricians confuse the cables at the time of installation. In projects, it is important to pick the cable a different color from the fire system cable!

Line / Area Structure of KNX TP

The TP bus cable described for KNX (see YCYM 2 × 2 × 0.8 or JY (St) Y: 2 × 2 × 0.8 TP structure). Konnex / KNX label is present on the cable. The standard green color KNX cable guarantees the following for TP:

Maximum cable length for a line,
Maximum distance between two devices in a line,
Maximum number of devices in a line,

These properties are ensured for 1000 meters of length: 75 ohms resistance and 100 nF capacity.

For other cables, technical specification documents should be checked.

The smallest line infrastructure in KNX infrastructure is as follows. Basically, the system includes a KNX Power supply, Actuator (Output element) and Sensor (Input elements such as switch, motion sensor, thermostat) that is connected to the KNX line. All these devices are located on the same knx communication line