What is KNX?
KNX is a wired bus standard (ISO/IEC 14543-3) for home and building automation. It's the most widely-deployed professional smart-home protocol in Europe, used in everything from single-family homes to airports and commercial buildings.
If you have an Atios KNX Bridge, KNX is the system it plugs into.
How KNX works
KNX devices are connected by a dedicated low-voltage bus cable — a twisted pair that carries both power and data. Typical bus voltage is below 30 V DC, fully separate from 230 V mains wiring.
All devices on the bus (switches, motion detectors, actuators, sensors) talk to each other by sending and receiving short telegrams addressed to group addresses. Press a wall switch assigned to the group address for "kitchen ceiling light" — and the actuator output wired to that light switches on.
Because addressing is done in software, rewiring is rare: to reassign a switch to a different light, you change its group address in ETS, not the cable.
What a KNX installation looks like
In the rooms you'll find low-voltage KNX devices:
- Wall switches and keypads
- Motion and presence detectors
- Temperature, humidity, and CO₂ sensors, weather stations
- Door and window contacts
All of these connect via the green KNX bus cable.
In the electrical cabinet, on the DIN rail:
- KNX power supply — powers the bus
- Actuators — switch/dim outputs that receive signals from the bus and drive lights, blinds, heating valves, sockets
- KNX IP Interface — needed to program the system from a computer running ETS
- KNX-DALI Gateway — optional, if you're using DALI-addressable luminaires
- App server / Matter Bridge — optional, for smartphone and voice control
The Atios KNX Bridge combines the last three items (IP Interface, KNX-DALI Gateway, and Matter Bridge) into one DIN-rail device.
Why KNX
- Manufacturer-independent — the KNX standard is supported by over 600 manufacturers worldwide. You can mix actuators from one brand, switches from another, sensors from a third.
- Long lifetime — installations from the 1990s are still running. Spare parts are generally available for decades.
- Scales up and down — same protocol works for an apartment, a villa, or a 40-storey office tower.
- Low-voltage signalling — no 230 V to push-buttons, safer and simpler to wire.
- Topology flexibility — reassigning devices is a software change, not a rewire.
Programming: ETS
KNX systems are commissioned with ETS (Engineering Tool Software), the official KNX Association programming tool. ETS is where you assign physical addresses, define group addresses, and download device behaviour.
You only need ETS once during commissioning. Day-to-day control — scenes, automations, app access — happens through a visualisation server or a Matter Bridge like the Atios KNX Bridge, not in ETS.
Where KNX is the right choice
- New builds where cabling is being installed anyway
- Villas and detached houses with many rooms, multiple floors, and long-term future-proofing
- Commercial and hospitality projects that need long product lifetimes and vendor flexibility
If your project doesn't have KNX and you don't plan to install it — an Atios SmartCore may be a better fit. See What is Matter? for how the two approaches differ.
How Atios connects to KNX
The Atios KNX Bridge sits on the KNX bus in the electrical cabinet and acts as three devices in one:
- KNX IP Interface — so ETS can program the KNX system over the network
- KNX-DALI Gateway — so DALI luminaires appear as normal KNX devices
- Matter Bridge — so the whole KNX installation appears in Apple Home, Google Home, Alexa, or SmartThings