01
How does KNX work, in simple terms?
In conventional wiring, a switch breaks the lamp circuit directly. In KNX, a pushbutton, a touch panel or a sensor sends a command over the bus, and an actuator — the device that switches the load — turns on the light, moves the blinds or opens a heating valve. Which button controls what is set during configuration, not by the wiring. That is why one press can start a whole scene: "Leaving home", "Cinema", "Night".
How a command travels in KNX
Command
Tecla keypad- Presence detector
KNX TP bus
- Twisted pairtelegrams between devices
Bus power supply
Actuation
Load
- Lighting
- Blinds
- Fan coil
02
What happens if one KNX device fails?
The other devices keep working. KNX has no central controller: the intelligence is distributed among the devices, and the failure of one does not stop the rest[3]. The exception is the power supply: it powers the twisted-pair cable the devices are connected to[2], so a system on a single line with a single power supply has a single point of failure[6]. An article on the KNX Association website recommends dividing a large installation into lines, each with its own power supply[6]; the supply is sized by the total current of the devices on its line[7].
Two more principles of the standard are backward compatibility — new KNX devices work with older installations, so a system can be extended years later — and open specifications that no single company controls[3]. According to KNX Association, systems installed decades ago are still working[3].
03
Who develops KNX, and which standards define it?
The technology grew out of the European EIB bus. The EIBA association was founded in 1990, and in 1999 the EIB, BatiBUS and EHS associations merged into the Konnex Association[3] — today KNX Association, headquartered near Brussels[4]. It is a non-profit organisation under Belgian law, set up to develop and promote the standard[3].
Key milestones of KNX
| Year | Milestone |
|---|---|
| 1990 | European Installation Bus Association (EIBA) founded |
| 1999 | EIB, BatiBUS and EHS merge into the Konnex Association (KNX Association) |
| 2002 | First version of the KNX specification published |
| 2003 | KNX approved as the European standard CENELEC EN 50090 |
| 2006 | KNX approved as the international standard ISO/IEC 14543-3 |
| 2013 | KNX adopted in China as the recommended national standard GB/Z 20965 |
| 2015 | KNX Secure launched (KNX Data Secure and KNX IP Secure) |
| 2019 | KNX IP Secure recognised as the international standard EN ISO 22510 |
| 2021 | ETS6 released |
| 2022 | KNX Standard 3.0 introduces KNX IoT |
| 2023 | Open-source KNX IoT stack and the first KNX IoT devices |
| 2024 | ETS6.3 with KNX IoT support |
04
What does a KNX system consist of?
- Control devices — pushbuttons, touch panels, presence, temperature and light sensors. In the Zennio range these are touch panels, Flat and Tecla keypads and sensors.
- Actuators — the devices that switch the loads. In our catalogue relays for lighting and sockets and blind actuators are in Actuators, dimmers in Lighting, heating and fan coil controllers in Climate.
- System devices — the bus power supply, line couplers, KNX-IP interfaces and routers: the System category. A KNX power supply is required on twisted pair[2].
A minimal wired KNX system
- Bus power supply
Powers the KNX TP line: 640 mA in total for the bus and the 29 V DC auxiliary output, short-circuit protection, DIN rail mounting[7].
- Actuator in the panel
12 outputs — up to 12 individual loads, up to 6 shutters or up to 3 two-pipe fan coils — and 12 inputs for sensors and pushbuttons[8].
- Control in the room
Capacitive keypad with RGB backlight and custom icons; a thermostat, a temperature sensor and a proximity sensor inside[9].
Transmission media: TP, RF, IP and KNX IoT
| Medium | What it is | Where it is used |
|---|---|---|
| KNX TP | Twisted pair — the most established and widely deployed KNX medium | New builds and major renovations |
| KNX RF | Radio on a dedicated sub-GHz frequency, joined to TP through segment couplers | Retrofits without new cabling |
| KNXnet/IP | KNX telegrams over IPv4 networks: routing, tunnelling, remote access | Building backbone, links to PCs and servers |
| KNX IoT | An IPv6 communication layer over Ethernet, Wi-Fi or Thread; a KNX IoT Router links it to TP, RF and IPv4 | Integration with IT and IoT systems |
KNX TP or KNX RF: which to choose?
Twisted pair is the main KNX medium: a dedicated bus cable designed for building automation gives reliable, predictable communication[2]. It is laid in a new building or during a major renovation, when the cable can go into the walls[2]. KNX RF works by radio at sub-GHz frequencies and is compatible with twisted pair. Radio devices go where a cable cannot: retrofits without opening walls, battery-powered sensors, wall-mounted transmitters and remote zones[2].
That is why one project often combines both: the bus in the panel and the walls, radio at individual points. The KNX RF section of Zennio's 2026 catalogue has three 868 MHz devices: the ZMCoup RF 868 media coupler, which links the radio devices to twisted pair, the WinDoor RF v2 radio window and door contact, and the EyeZen RF 868 ceiling motion detector[12]. Zennio makes no radio actuators or radio switches: even in such a system the loads are switched by wired actuators in the panel.
KNX IoT: what KNX Standard 3.0 changed
KNX Association released version 3.0 of the KNX Standard to its members on 22 April 2022. It was the first official publication of the KNX IoT 3rd Party API and KNX IoT Point API specifications: they make a KNX installation reachable through RESTful web services and allow KNX devices for IPv6 networks such as Thread[13]. The open-source KNX IoT stack and the first devices followed in 2023[3].
Topology: lines, areas and devices per line
Devices on twisted pair are grouped into lines. Line couplers connect the lines over a backbone: up to 15 lines form an area, and up to 15 areas are joined by area couplers. Instead of a TP backbone, IP can be used — a KNX IP router links several TP sections over IP[2]. This is how one system scales from an apartment to a multi-storey hotel.
Under the TP1-256 topology one line takes up to 256 devices without line repeaters, but in practice the number is usually limited by the power supply current, not by addressing: an article on the KNX Association website notes that with the common 640 mA supplies most lines still carry around 64 devices[15]. Zennio datasheets list an integrated KNX bus coupler of the TP1-256 type, for example on Tecla RGB[9].
05
ETS: one tool for every manufacturer
ETS is the planning and configuration tool that brings all KNX devices into one installation[1]. KNX Association offers a free online ETS course on its KNX eCampus platform[16]. As of June 2025, 500 KNX training centres in 71 countries had certified more than 135,000 people as KNX Partners[3]. The route to KNX Partner status is a KNX Basic Course at an approved training centre followed by an exam[17]; certified installers are shown on KNX Association's map as Silver, Gold or Platinum Partners[18].
06
Does KNX work without the internet, and how is it secured?
Yes. The core functions of KNX run locally and do not rely on constant internet access[1]: lights, climate and blinds keep working when the connection to the cloud is lost. Data in transit are protected by KNX Secure, which adds authentication and encryption: KNX Data Secure secures the communication within the KNX installation, KNX IP Secure the communication over the IP network[19]. Many Zennio devices support KNX Secure, as their datasheets state — for example Tecla RGB[9] and the KIPI SC secure KNX-IP interface[11].
07
When is KNX the right choice, and when is it not?
- Open standard
KNX certification ensures that products from different manufacturers work together[2].
- Works without the internet
Core functions run locally; the cloud is needed only for remote access[1].
- From an apartment to a building
Lines are joined into areas, and the backbone can run over IP[2].
- KNX Secure
KNX Data Secure secures the communication within the installation, KNX IP Secure the communication over the IP network[19].
Zennio itself names reliability, security, freedom to choose manufacturers, modularity, scalability and compatibility as the strengths of KNX, and the need to lay the bus and to train qualified specialists as its limitations[20]. That is why KNX is planned at the design and renovation stage and configured by a trained integrator.
- Apartment or house — lighting, climate, blinds, scenes and mobile control: see smart home on KNX.
- Hotel — guest room management (GRMS), Do Not Disturb and Make Up Room statuses, energy saving: see smart hotel, the guide How to build a KNX hotel room and the GRMS specification checklist.
- Office or commercial building — lighting by presence, climate by zone, integration with the building management system: see building automation.
08
How does a KNX system get into a home?
- 1Scenes and tasks
First, the list of what must be controlled: lighting, blinds, climate, scenes such as "Leaving", "Night", "Cinema". It decides the set of devices.
- 2Design and device selection
The integrator divides the devices into lines, matches actuators to the loads and panels to the rooms, and sizes the power supply by the consumption of the line[7].
- 3Bus during the renovation
Wired KNX needs the bus cable to be laid, so it goes in before the finishing work[20].
- 4Installation
The power supply, actuators and interfaces go onto the DIN rail in the panel[7], the panels and keypads into the walls.
- 5Programming in ETS
All devices are configured in one program, ETS[1]; the computer connects to the bus through a USB or IP interface[10]. Scenes and logic are set there too.
- 6Handover and growth
New scenes and moving functions between buttons are a matter of reconfiguring ETS, not rewiring.
09
Zennio, a KNX manufacturer — and KNX in Kazakhstan
Zennio is a Spanish manufacturer of KNX devices, founded in 2005 in Toledo, where its headquarters and manufacturing facilities are located[21]. Its products are present in more than 123 countries[22], and its quality management system is ISO 9001 certified[23]. Zennio is a member of KNX Association[4] and an accredited KNX Test Lab, including KNX Secure tests[5].
We are ZENNIO Kazakhstan, the official Zennio distributor in Kazakhstan: our office is in Almaty, and we supply KNX equipment across the country. We help select the devices and prepare the specification; installation and programming are done by KNX integrators. To look for a certified KNX installer near a project in Kazakhstan, use the map of KNX Partners on KNX Association's website[18]. More about the manufacturer is on the About Zennio page; to discuss a project, write to us.