KNX technical glossary
117 terms
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117 technical terms grouped into 21 categories: KNX topology, communication, ETS, security, standards, etc. Type a keyword or browse by category.
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File extension of a manufacturer product catalogue. Signed by the manufacturer, importable into ETS to add a device to the local catalogue. Not to be confused with .knxproj (project).
File extension of an exported ETS project. It is in fact a ZIP archive containing Project.xml + manufacturer catalogues + integrity signatures.
ETS tool that observes telegrams at the raw frame level. Displays source addresses, priorities, ACK/NACK, repetition counters. For low-level technical diagnostics.
Proprietary KNX Association software for commissioning installations. Versions: ETS3 (2002), ETS4 (2010), ETS5 (2014), ETS6 (2021, current). Variants: Lite (20 devices max), Pro (unlimited), Demo (free, 5 devices).
Third-party extensions installable in ETS via the KNX Association Marketplace. Examples: Project Tracing, Reverse Engineering, IP Wizard, Replace Device.
ETS version limited to 20 devices per project. Sufficient for simple residential installations. Voucher of -12.5% offered after passing KNX Basic.
ETS version with unlimited number of devices. Standard for professional projects. Cost ~1100 € one-shot license, -12.5% voucher after KNX Basic.
Complete download: individual address + application program + parameters + bindings. Slower than Partial Download but guarantees full consistency.
ETS tool that observes telegrams in real time at group address level, with automatic DPT decoding. Useful to verify the functional behaviour of an installation.
KNX Association web platform. A free account provides access to: download of the public KNX Specifications V3.0.0, management of individual certifications, ETS vouchers, online theory exam.
Download of ONLY the parameters modified since the last download. Fast. Automatically selected by ETS when changes are minor.
Physical button on every KNX device, to be pressed during initial download of the individual address. Lights up an LED while waiting. Automatic timeout after a few minutes.
ETS command that completely erases a component's configuration (address, application, parameters) and resets it to factory default (address 0.0.0). Useful before reusing in another project.
16-bit logical identifier used to group together group objects of different components so that they can communicate. Displayed in 2-level structure (Main/Sub) or 3-level structure (Main/Middle/Sub).
Unique identifier of a KNX component within the installation, format A.L.D (Area.Line.Device). Range 0-15 / 0-15 / 0-255. Address 0.0.0 = factory default, 15.15.255 is reserved for tools.
Component connecting an area to the backbone. Same principles as a Line Coupler but at a higher level. Conventional address: A.0.0.
Top level of the topology, identified as "area 0" in ETS. Connects the areas via Area Couplers. Can be TP1 (Backbone TP) or IP (Backbone IP, recommended in modern commercial projects).
List of group addresses that a Line Coupler or Area Coupler must route. Any group address not present is filtered locally. Computed automatically by ETS, can be edited manually.
Component acting as a gateway between IP and TP. Can operate as Line Coupler, Area Coupler or IP backbone element in Tunneling or Routing multicast mode.
Intermediate level of the KNX topology. Contains up to 64 components per segment, extendable to 256 with repeaters (max 4 segments). Maximum 15 lines per area.
Component connecting a sub-line to the main line of its area. Filters telegrams according to its filter table. Conventional individual address: A.L.0.
Component that amplifies and forwards telegrams in order to extend a line over multiple segments (up to 4 × 64 = 256 devices). Does not filter, unlike the Line Coupler.
Physical portion of a line, powered by a dedicated PSU. Maximum 64 components per segment. A line can comprise up to 4 segments connected via Line Repeaters.
Hierarchical organisation of a KNX installation in 3 levels: Segment (physical) → Line (logical) → Area → Backbone.
Top hierarchical level in the KNX topology. Contains up to 15 sub-lines + 1 main line. Maximum 15 areas per installation + 1 backbone (area 0 is reserved).
Positive acknowledgement sent by the receiver of a correctly received telegram. Link-layer mechanism that lets the sender know whether its telegram was received.
Acknowledgement indicating that the receiver is too busy to process the telegram. Asks the sender to retry later.
"Carrier Sense Multiple Access with Collision Avoidance": bus arbitration mechanism for KNX TP1. Exploits the dominant character of bit 0 to resolve collisions without destroying the telegram.
Cyclic sensor emission mode: periodically send the current value regardless of changes. Useful to refresh visualizations and detect outages.
Negative acknowledgement sent in case of a checksum or format error detected by the receiver. Triggers a retransmission by the sender.
Four levels coded in the telegram: System (highest), Alarm, High, Normal. CSMA/CA arbitration exploits the dominant character of 0 bits to resolve collisions according to priority.
Telegram field indicating how many times it has been retransmitted following a missing ACK or a NACK. Visible in Bus Monitor. High counter = bus problem.
Sensor emission mode: send a telegram only if the value changes by a configured delta since the last sending. Reduces bus load.
Transmission unit on the KNX bus. Contains: preamble, control, source address (16 bits), destination address (16 bits), flags, length, data (0-14 bytes), checksum, ACK.
Timer on a receiving Group Object: if no telegram is received within the configured window, switches to a safe fallback state. Assumes the sender is in Cyclic Send.
Semantic typing of data transmitted on the KNX bus. Format `m.nnn`: family (1 to 251+) + sub-type (precise semantics). Standardised in KNX Specifications Vol. 3/7/2.
1-bit on/off boolean. Most common use: light switching, state of an on/off actuator.
1-bit up/down boolean (same structure as DPT 1.001, different semantics). Typical use: blind and roller shutter control.
32-bit IEEE 754 single-precision float family. Higher precision and range than DPT 9.xxx. Use: energy meters, scientific measurements (DPT 14.056 power W, 14.027 electric flux, etc.).
1-byte scene number 0-63. Allows the RECALL of a scene (recall only), without storage capability.
1-byte scene control: 1 bit "learn/recall" + 1 reserved bit + 6 bits scene number 0-63. Allows both recall AND storage of a scene in a single telegram.
1-byte HVAC mode enumeration: Comfort (1), Standby (2), Economy (3), Building Protection (4). Standard for heating and air-conditioning control in KNX.
3-byte RGB colour (1 byte per R, G, B component). Use: RGB LED lighting control. On DPT 251.600, a 4th byte is added for the white channel (RGBW).
1-byte 0-100 % percentage. Coding: 0 = 0 %, 255 = 100 %. Use: light dimming, blind position, valve opening ratio.
Temperature in °C on 2 bytes (KNX 16-bit float). Precision and range suited to home automation/HVAC uses. KNX proprietary format, not IEEE 754.
Open protocol for building automation and control, standardised as ASHRAE 135 and ISO 16484-5. Supports multiple physical layers (BACnet/IP, MS/TP, Ethernet). Extensible object-property model for HVAC, lighting and access control.
MAC protocol for low-power wide-area networks, defined by the LoRa Alliance. Built on LoRa modulation (CSS, Semtech). Star-of-stars architecture: end-devices → gateways → Network Server. Operates on ISM bands (EU868, US915…).
Interoperability standard for smart home devices, published by the CSA (Connectivity Standards Alliance). Built on IP (Wi-Fi, Thread, Ethernet) and secures sessions via PASE/CASE. Native interoperability across Apple, Google, Amazon and Samsung ecosystems.
Serial communication protocol published in 1979 by Modicon, now a de facto standard for industrial automation. Based on a master/slave model with addressable registers; available as Modbus RTU (binary), ASCII and TCP/IP.
Unified communication architecture defined by the OPC Foundation (IEC 62541), service-oriented and platform-independent. Replaces OPC Classic (DCOM). Exposes a structured address space (nodes, references) accessible via session or Pub/Sub.
Serial fieldbus standardised as IEC 61158/IEC 61784, maintained by PI (PROFIBUS & PROFINET International). Available as DP (decentralised periphery, up to 12 Mbit/s) and PA (process automation, bus-powered). Massive installed base in industry.
Industrial real-time Ethernet standard defined by PI (PROFIBUS & PROFINET International) and standardised as IEC 61158/IEC 61784. Three performance classes: NRT, RT and IRT (cycle < 1 ms). Replaces PROFIBUS on new installations.
IPv6 mesh network protocol based on IEEE 802.15.4, specified by the Thread Group. No single point of failure (self-healing mesh), battery-powered. Preferred network layer for Matter in smart homes.
Code in a Modbus exception response (Function Code + 0x80) indicating the reason for refusal: 01 (illegal function), 02 (illegal data address), 03 (illegal data value), 04 (slave device failure). Enables quick diagnosis without reading status registers.
One-byte field in the Modbus PDU identifying the action requested by the master: read coils (01), read registers (03), write (06/16), etc. A code > 0x7F in the response signals an exception.
Text file (.gsd extension) describing the characteristics of a PROFIBUS slave: modules, parameters, cycle time, manufacturer ID. Required by the master configuration tool to integrate the slave into a project.
XML file (.gsdml extension) describing a PROFINET IO device: modules, sub-modules, parameters, DAP (Device Access Point). Evolving towards PNXML format. Used by the engineering tool for automatic device integration.
Media Redundancy Protocol defined in IEC 62439-2, used in ring-topology PROFINET networks. One MRM (Media Redundancy Manager) monitors the ring; on link failure, reconfiguration is guaranteed in under 200 ms (standard mode).
Unique identifier for a node in the OPC UA address space, composed of a namespace (NamespaceIndex) and an identifier (numeric, string, GUID or opaque). Used as a stable reference for subscriptions and reads.
Functional safety profile for PROFIBUS and PROFINET, standardised as IEC 61784-3. Adds an F application layer (F-Address, CRC, consecutive number, watchdog) on top of the standard protocol to achieve SIL 3 / Cat. 4 without dedicated wiring.
OPC UA communication model defined in Part 14 of the specification (IEC 62541-14). Decouples publishers and subscribers via DataSets published to a broker (MQTT/AMQP) or UDP multicast. Complements the client-server model for real-time data streams.
Predecessor standard of KNX, created in 1990 by EIBA in the German-speaking region. Upward compatibility is preserved: an EIB component can operate on a KNX TP1 bus.
Family of European standards EN 50090 covering electronic building management systems for residential and commercial buildings. KNX is its main implementation.
Open fieldbus standard for home and building automation, created in 2002 by the merger of the EIB (DACH), EHS and BatiBUS standards. Maintained by the KNX Association cvba (Brussels).
Non-profit organisation (cvba under Belgian law) based in Brussels, founded in 1999. Maintains and develops the KNX standard, certifies products and training centres, and licenses the KNX® trademark.
Company member of the KNX Association authorised to manufacture KNX-labelled components (Hager, Gira, ABB, Schneider, JUNG, Theben, etc.). Around 500 manufacturer members worldwide.
Company member of the KNX Association with professional integrator status. Must have at least one certified KNX Partner on its team. Membership fee ~500 €/year.
Certification following the Basic. 30h course, 13 official topics (couplers, HVAC, lighting, logic, etc.), theory + practical exam mandatory in-person, 50% threshold. Price 1500-2050 € HT (FR).
Entry-level certification issued by KNX Association. 30h course (5 days), 1h30 theory exam + 1h30 practical, T/F format, scoring +1/-0.5/0, 50% threshold. Price 1200-1500 € HT (FR).
Process by which KNX Association certifies products (interoperability, conformity) and people (Basic, Advanced, Tutor). Annual product re-certification.
Suite of interoperability tests passed by KNX products in accredited laboratories, verifying conformity to the standard. Prerequisite for the KNX logo.
Individual title awarded after passing the KNX Basic certification. Personal status (not company-bound), transferable between employers.
Certification authorizing teaching in a certified KNX center. 18h course, theory only, 60% threshold. Prerequisites: Advanced passed. Niche audience.
KNX transport over Ethernet/Wi-Fi via UDP. Two modes: Tunneling (point-to-point unicast) and Routing (multicast 224.0.23.12). Recommended as backbone in commercial buildings.
KNX radio transport on the 868.3 MHz band, Manchester coding, 16.384 kbit/s. Two generations: RF Ready (single-channel, legacy) and RF Multi (multi-channel, recommended).
KNX transport over the 230 V mains line, 110 kHz carrier (CENELEC band B). Rarely deployed in new builds since 2010, only found in existing installations.
KNX IP multicast communication mode (224.0.23.12) between IP Routers. All routers in the VLAN listen and forward. Standard for IP backbones.
Main physical layer of KNX: twisted-pair bus at 30 V DC SELV, 9600 bit/s. The most widely deployed in residential and commercial installations.
KNX IP point-to-point unicast communication mode to an IP Interface. Used for remote ETS commissioning or targeted diagnostics.
Communication flag of a Group Object. Enabled = the GO can participate in bus traffic. Disabled = GO is completely ignored. Prerequisite for all other flags.
Flag that triggers a Group Value Read on device startup (bus voltage return) in order to retrieve the current state of partner devices. Use sparingly (traffic spike at reset).
Flag allowing the GO to respond to Group Value Read telegrams from the bus. Enable only when the value needs to be readable on request.
Flag allowing the GO to send a Group Value Write on the bus when its value changes locally.
Flag allowing the GO to update its internal value when receiving a Group Value Response (for example in response to a read sent by another device).
Flag allowing the GO to receive Group Value Write telegrams from the bus. Without W, external writes are ignored (GO is read-only).
Encryption and authentication at the application layer (group object) level, end-to-end between components. AES-128 CCM. Protects the value of a specific group object.
UDP equivalent of TLS. Used by KNX IP Secure to encrypt/authenticate the UDP datagrams of KNXnet/IP, both in tunneling and in multicast routing.
Factory key printed on the label of a KNX Secure component (QR code + 32-char hex string). Used by ETS during the first integration into the Secure project. Must be kept separately.
Encryption at the IP transport layer (between IP Routers or via tunneling). Uses DTLS. Protects IP traffic, transparent to downstream TP components.
Family of cryptographic security mechanisms in KNX, available as Data Secure (application layer) and IP Secure (IP transport). Natively integrated in ETS6.
Special key in the keyring that allows an ETS tool to reprogram an already-deployed Secure device without rescanning the original paper FDSK.
Adaptive Data Rate: LoRaWAN algorithm that dynamically adjusts the Spreading Factor and transmit power based on link quality (SNR/RSSI). Optimises throughput and battery life for static end-devices.
Regulatory limit imposed by the ERC on the EU868 band: an end-device may transmit for only 1% of the time on a sub-band (36 s/h). Impacts message send frequency and LoRaWAN application sizing.
Two LoRaWAN activation methods. OTAA (Over-The-Air Activation): dynamic join procedure deriving session keys from AppKey and NwkKey. ABP (Activation By Personalization): keys and DevAddr statically pre-configured, no join procedure required.
Two secure session establishment protocols in Matter (CSA). PASE (Passcode Authenticated Session Establishment) is used during initial commissioning via a PIN code. CASE (Certificate Authenticated Session Establishment) secures operational exchanges using NOC (Node Operational Certificate) certificates.
LoRa parameter (SF7 to SF12) controlling signal spreading: a higher SF increases range and robustness but reduces data rate and increases Time-on-Air. SF7 ≈ 5.47 kbps; SF12 ≈ 293 bps at BW125.
Inductive component built into KNX TP1 bus power supplies. Decouples the high-frequency telegram transmission from the DC supply current, which is essential for operation.
Standard cable type for the KNX TP1 bus: 2 shielded twisted pairs, 0.8 mm² conductors. Conventional green sheath colour (not mandatory).
Power supply dedicated to the KNX TP1 bus, delivers 30 V DC SELV with integrated choke. Standard capacities: 160 mA, 320 mA, 640 mA. NEVER use to power anything other than the bus.
Electrical classification for Safety Extra-Low Voltage. The KNX TP1 bus (30 V DC) is classified as SELV: it may share conduits with other SELV circuits, but must be kept separate from 230 V wiring.
Feature of the KNX theory exam: the candidate is allowed to consult the paper or PDF course documentation during the test. Encourages understanding rather than pure memorization.
KNX scoring mechanism: correct answer = +1, wrong = -0.5, blank = 0. Encourages abstaining on uncertain questions (negative expected value of a wrong guess).
Official format for the theory questions of KNX Basic and Advanced. Each statement must be validated as True or False. Asymmetric scoring: +1 correct, -0.5 wrong, 0 blank.
Closed-loop control to maintain a constant illuminance (e.g. 500 lux) by compensating for natural light. Energy savings of 30-60% vs all-or-nothing switching.
Lighting protocol (Digital Addressable Lighting Interface). Integrable in KNX via a DALI Gateway. Allows individual control of up to 64 DALI ballasts per DALI bus.
Predefined configuration of multiple actuators (lighting, blinds, HVAC, audio) triggered by a single telegram (DPT 17.001 or 18.001). Numbered 0-63.
French decree no. 2019-771 (23 July 2019) on mandatory energy reduction actions in tertiary-sector buildings (floor area ≥ 1,000 m²). Requires −40% by 2030, −50% by 2040 and −60% by 2050 relative to a reference year. Specific to France.
International Performance Measurement and Verification Protocol, published by the EVO (Efficiency Valuation Organization). Methodological framework for measuring and verifying energy savings from energy efficiency projects. International reference for Energy Performance Contracts (EPC).
Digital platform of the French ADEME agency for entities subject to the French tertiary sector energy-saving obligation (Décret Tertiaire, decree no. 2019-771) to report annual energy consumption and track reduction targets. This is a French regulatory tool.
Series of European standards for Home and Building Electronic Systems (HBES). KNX complies with EN 50090. Several parts: architecture, performance, safety, etc.
International standard "Information technology — Home Electronic System (HES) Architecture" which codifies KNX at the ISO/IEC level. Reference for non-European markets.
Operating mode of the heating/cooling system. 4 standard modes (DPT 20.102): Comfort, Standby, Economy, Building Protection. Cascade regulation according to priorities.
Pulse width modulation: cyclic on/off signal (typ. 10-15 min) whose duty cycle determines the average. Used to drive electrothermal thermostatic valves from a DPT 1.001.
BACnet Broadcast Management Device: hardware or software function that relays BACnet/IP broadcast messages between separate IP subnets. Enables device discovery (Who-Is/I-Am) and COV distribution across routed architectures.
Change of Value: BACnet mechanism allowing a client to subscribe to changes in an object property. The server sends notifications only when the value exceeds a configurable increment (COV Increment), reducing traffic compared to polling.