Wiki

An actuator is the KNX device that does something: switch, dim, move, position. It listens to group addresses and carries out what a sensor has sent. Actuators almost always sit on the DIN rail in the distribution board, because that is where the load they switch is located.

A sensor is the KNX device that reports something: a key press, a temperature, a movement, an open contact. It sends telegrams to a group address and does not know who receives them. Sensors sit where measuring or operating happens, meaning in the room rather than in the distribution board.

The bus coupling unit is the part of a KNX device that talks to the bus. It sits between the two-wire bus line and the actual device, converts telegrams into data and carries the individual address. In modern devices it is built into the housing; as a separate component it is mainly encountered with flush-mounted operating elements.

Forced control and locking are two different ways of temporarily taking control away from an actuator. Forced control prescribes a state to it; locking merely forbids it to listen to normal commands. The two are regularly confused, and the consequence only shows once the force is released.

A KNX group address (GA) is a logical address that links communication objects (COs) of different devices. Whatever is written to a GA is received by all other COs bound to that GA, the publish-subscribe principle of KNX.

A communication object (CO) is a data point on a KNX device. It has a type (DPT), a direction (send/receive), and is linked to COs on other devices via group addresses.

A data point type (DPT) defines the format and value range of a KNX communication object. Two COs that communicate must share the same DPT, otherwise the receiving device misinterprets the data.

KNX flags control the behaviour of a communication object on the bus. They define whether a CO can send, receive or respond to telegrams, and whether it requests a value on startup.

A KNX telegram is the smallest unit of communication on the bus. It contains sender (physical address), destination address (group address), data value and priority, and is received simultaneously by all devices on the line.

Every KNX device has an individual (physical) address in the format X.Y.Z, indicating its place in the topology. It is set once via ETS + programming button and is necessary for downloading the device configuration.

KNX energy metering captures current, voltage and consumption via KNX measuring devices, making them evaluable throughout the system via group addresses, creating a seamless consumption overview without a separate metering cloud.

KNX TP networks are hierarchically structured: devices form a line, lines are grouped into areas, areas are connected via the backbone. This structure supports up to 14,400 devices in a pure TP network.

KNX TP is the most widely used transmission medium. A twisted pair simultaneously transmits power (29 V DC SELV) and data (9,600 baud), all devices on a line share the same cable.

KNX TP devices are powered directly from the bus, the bus cable simultaneously transmits data and energy. The bus voltage is SELV (Safety Extra Low Voltage) and harmless to persons.

The KNX power supply provides the TP bus with 29 V DC SELV and delivers operating current to all bus participants. At least one power supply is required per line; with many devices, two can operate in parallel.

A KNX line coupler (LC) connects two lines and filters telegrams, only telegrams with destination GAs in the filter table are forwarded. It reduces bus load and provides galvanic isolation.

KNXnet/IP is the standard for KNX communication over IP networks. It enables remote ETS programming (tunneling) and connects multiple TP lines via an IP backbone (routing).

A KNX IP interface connects an ETS computer to the KNX bus over the LAN. Unlike an IP router, it does not forward telegrams between lines, it is exclusively a gateway for ETS and visualisation systems.

KNX RF is the wireless transmission medium for KNX devices without TP bus wiring. Ideal for retrofit installations in existing buildings where cables cannot be laid.

DALI (IEC 62386) is the standard protocol for electronic control gear (ECG) and LED drivers. A DALI-KNX gateway translates KNX telegrams into DALI commands, enabling precise, flicker-free dimming of individual luminaires, groups and scenes.

EnOcean devices harvest energy from light, movement or temperature differences, completely without battery and without cables. An EnOcean-KNX gateway makes these sensors visible in the KNX system and forwards their telegrams to the TP bus.

The KNX Engineering Tool Software (ETS) is the only official tool for configuring and commissioning KNX projects. Developed and maintained by the KNX Association, it runs on Windows.

The application program is the device-specific software a manufacturer supplies for its product. It determines which communication objects a device has, which parameters can be set and how it behaves. It reaches the ETS via the product database and the device during programming.

KNX commissioning is the step where ETS writes the finished configuration into the physical devices. It requires physical or IP access to the KNX bus and ETS Professional.

A .knxproj file contains the complete configuration of a KNX installation: building structure, all devices, all group addresses, all parameterisations and all GA-CO links. It is the central backup for every KNX installation.

A KNX installation should be fully planned before devices are ordered and cables installed. The planning process covers five phases: requirements analysis, design, device selection, ETS configuration and commissioning.

KNX visualisation systems enable graphical operation and monitoring of a KNX installation via touch panels, tablets or browsers, they complement push-button operation but do not replace the bus logic.

KNX bus diagnostics covers systematic analysis of telegram traffic, bus voltage measurement and physical cable routing. Using the ETS bus monitor and a multimeter, most faults can be located within minutes.

KNX Secure is the security standard for KNX communication. It protects bus telegrams against eavesdropping and manipulation, both on IP networks (IP Secure) and on the TP cable (Data Security).

A KNX scene stores the states of multiple devices as a single data point (DPT 17.001). When the scene is recalled, all associated actuators are simultaneously set to their stored values.

KNX was created in 1999 from the merger of three European bus systems: EIB (European Installation Bus), EHS (European Home System) and BatiBUS. The TP protocol of EIB/Instabus is technically identical to KNX, older EIB devices continue to work in KNX networks.

Every product bearing the KNX logo has been certified by the KNX Association and tested for interoperability with devices from other manufacturers. Certification is the central quality feature of KNX.

KNX is the world-leading open standard for building automation, standardised as ISO/IEC 14543-3 and EN 50090. It is used in residential, commercial and infrastructure projects in over 190 countries.

KNX, Matter, Zigbee and Z-Wave serve different use cases. KNX is the professional standard for new construction and professional installation, Matter, Zigbee and Z-Wave are cheaper but designed for DIY and retrofitting.