KNX technical glossary
89 technical terms grouped into 16 categories: KNX topology, communication, ETS, security, standards, etc. Type a keyword or browse by category.
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ETS
13 terms.knxprod
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).
.knxproj
File extension of an exported ETS project. It is in fact a ZIP archive containing Project.xml + manufacturer catalogues + integrity signatures.
Bus monitor
ETS tool that observes telegrams at the raw frame level. Displays source addresses, priorities, ACK/NACK, repetition counters. For low-level technical diagnostics.
Download All
Complete download: individual address + application program + parameters + bindings. Slower than Partial Download but guarantees full consistency.
Download Partial
ETS download of the required parts according to the download flags, including parameters and group addresses. It is not limited to changed parameters; the parts downloaded depend on the flags and device capabilities.
ETS
KNX Association software for designing and commissioning KNX installations. Versions: ETS3 (2004), ETS4 (2010), ETS5 (2014), ETS6 (2021). Commercial editions are distinct from versions: including Demo, Lite, Home and Professional; check current limits and conditions with KNX.
ETS Apps
Third-party extensions installable in ETS via the KNX Association Marketplace. Examples: Project Tracing, Reverse Engineering, IP Wizard, Replace Device.
ETS Lite
ETS Lite edition limited to 20 devices per project. Training licences and vouchers associated with KNX Partner certification have their own conditions and validity periods: check the current MyKNX terms before purchasing rather than assuming a fixed discount.
ETS Professional
ETS Professional edition without a commercial limit on devices per project. Prices and training vouchers depend on purchase type, eligibility and validity dates; consult the current KNX Association terms in MyKNX.
Group monitor
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.
MyKNX
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.
Programming button
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.
Unload
ETS distinguishes Unload Application (individual address retained) from Unload Application and Address (address reset to 15.15.255). These operations are distinct from a manufacturer reset of all product functions.
Topology
12 termsArea
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).
Backbone coupler
Component connecting an area to the backbone. Same principles as a Line Coupler but at a higher level. Conventional address: A.0.0.
Backbone line
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).
Filter table
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.
Group address
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).
Individual address
KNX device identifier in an installation, in area.line.device format (4/4/8 bits). 15.15.255 is used for unprogrammed devices and after unloading the application and address; 0.0.0 is not the general factory address. Device part .0 is used for couplers according to their topology position.
KNXnet/IP router
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.
Line
Logical level of the KNX TP topology. In the historical TP-64 model, a segment supports up to 64 devices and a line can have four segments with repeaters. TP-256 allows up to 256 devices on a compatible segment; verify devices, bus load and power supply before applying this limit. Up to 15 secondary lines per area.
Line coupler
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.
Line repeater
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.
Segment
Physical part of a KNX TP line supplied through a suitable choke. The historical TP-64 limit is 64 devices; TP-256 can allow 256 devices on a compatible segment. Current, cable, distance and compatibility limits still apply; one power-supply enclosure may provide several suitable outputs.
Topology
Hierarchical organisation of a KNX installation in 3 levels: Segment (physical) → Line (logical) → Area. The areas are linked to each other by the backbone line.
Communication
10 termsACK
Positive acknowledgement sent by the receiver of a correctly received telegram. Link-layer mechanism that lets the sender know whether its telegram was received.
BUSY
Acknowledgement indicating that the receiver is too busy to process the telegram. Asks the sender to retry later.
CSMA/CA
"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 sending
Cyclic sensor emission mode: periodically send the current value regardless of changes. Useful to refresh visualizations and detect outages.
NACK
Negative acknowledgement sent in case of a checksum or format error detected by the receiver. Triggers a retransmission by the sender.
Repetition counter
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.
Send on change
Sensor emission mode: send a telegram only if the value changes by a configured delta since the last sending. Reduces bus load.
Telegram
Transmission unit on the KNX bus. Contains: control, source address (16 bits), destination address (16 bits), address type + routing counter + length, payload (1 bit to 14 bytes), checksum. The acknowledgement (ACK) is a separate short frame sent by the receivers.
Telegram priority
Four levels coded in the telegram: System (highest), Alarm, High, Low (lowest). CSMA/CA arbitration exploits the dominant character of 0 bits to resolve collisions according to priority.
Watchdog
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.
Datapoint Types (DPT)
10 termsDPT
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.
DPT 1.001
1-bit on/off boolean. Most common use: light switching, state of an on/off actuator.
DPT 1.008
1-bit up/down boolean (same structure as DPT 1.001, different semantics). Typical use: blind and roller shutter control.
DPT 14.xxx
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 potential V, etc.).
DPT 17.001
1-byte scene number 0-63. Allows the RECALL of a scene (recall only), without storage capability.
DPT 18.001
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.
DPT 20.102
1-byte HVAC mode enumeration: Comfort (1), Standby (2), Economy (3), Building Protection (4). Standard for heating and air-conditioning control in KNX.
DPT 232.600
DPT 232.600 encodes RGB in 3 bytes. DPT 251.600 encodes RGBW in 6 bytes: four 8-bit colour components, 12 reserved bits and 4 validity flags (U8U8U8U8r8r4B4). Four channels do not mean four bytes in total.
DPT 5.001
1-byte 0-100 % percentage. Coding: 0 = 0 %, 255 = 100 %. Use: light dimming, blind position, valve opening ratio.
DPT 9.001
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.
System
6 termsEIB
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.
HBES
Family of European standards EN 50090 covering electronic building management systems for residential and commercial buildings. KNX is its main implementation.
KNX
Open standard for building automation. The convergence of the EIB, EHS and BatiBUS organisations dates to 1999; the KNX specification was published in 2002. These events are distinct from the foundation of EIBA in 1990 and ISO recognition in 2006.
KNX Association
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.
KNX manufacturer
Company member of the KNX Association authorised to manufacture KNX-labelled components (Hager, Gira, ABB, Schneider, JUNG, Theben, etc.). Around 500 manufacturer members worldwide.
KNX system integrator
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.
Physical media
6 termsKNX IP
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 PL110
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 RF
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 TP
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.
Routing
KNX IP multicast communication mode (224.0.23.12) between IP Routers. All routers in the VLAN listen and forward. Standard for IP backbones.
Tunneling
KNX IP point-to-point unicast communication mode to an IP Interface. Used for remote ETS commissioning or targeted diagnostics.
Flags
6 termsCommunication (C) flag
Communication flag of a Group Object. Enabled = the GO can participate in bus traffic. Disabled = GO is completely ignored. Prerequisite for all other flags.
Read (R) flag
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.
Read on Init (I) flag
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).
Transmit (T) flag
Flag allowing the GO to send a Group Value Write on the bus when its value changes locally.
Update (U) flag
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).
Write (W) flag
Flag allowing the GO to receive Group Value Write telegrams from the bus. Without W, external writes are ignored (GO is read-only).
KNX Secure
6 termsData Secure
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.
DTLS
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.
FDSK
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.
IP Secure
Encryption at the IP transport layer (between IP Routers or via tunneling). Uses DTLS. Protects IP traffic, transparent to downstream TP components.
KNX Secure
Family of cryptographic security mechanisms in KNX, available as Data Secure (application layer) and IP Secure (IP transport). Natively integrated in ETS6.
Tool key
Special key in the keyring that allows an ETS tool to reprogram an already-deployed Secure device without rescanning the original paper FDSK.
Certification
5 termsKNX Basic
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.
KNX certification
Process by which KNX Association certifies products (interoperability, conformity) and people (Basic, Advanced, Tutor). Annual product re-certification.
KNX conformance tests
Suite of interoperability tests passed by KNX products in accredited laboratories, verifying conformity to the standard. Prerequisite for the KNX logo.
KNX Partner
Individual title awarded after passing the KNX Basic certification. Personal status (not company-bound), transferable between employers.
KNX Tutor
Certification authorizing teaching in a certified KNX center. 18h course, theory only, 60% threshold. Prerequisites: Advanced passed. Niche audience.
Cabling
4 termsChoke
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.
J-Y(St)Y
Shielded twisted-pair cable. In 2×2×0.8, 0.8 mm is the conductor diameter, equivalent to approximately 0.50 mm² cross-section. Use a suitable/approved KNX TP variant according to its manufacturer data sheet; the J-Y(St)Y designation alone does not guarantee all KNX cable characteristics.
Power supply unit
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.
SELV
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.
Exam
3 termsAsymmetric scoring
KNX Basic theoretical scoring: +1 for a correct answer, −0.5 for a wrong answer, 0 for a blank. With probability p of being correct, expected points are 1.5p − 0.5: positive if p > 1/3. An equally likely true/false choice averages +0.25 points; this average does not guarantee passing an exam.
Open-book
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.
True/False
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.
Standards
2 termsEN 50090
Series of European standards for Home and Building Electronic Systems (HBES). KNX complies with EN 50090. Several parts: architecture, performance, safety, etc.
ISO/IEC 14543-3
International standard "Information technology — Home Electronic System (HES) Architecture" which codifies KNX at the ISO/IEC level. Reference for non-European markets.
HVAC
2 termsHVAC mode
Operating mode of the heating/cooling system. 4 standard modes (DPT 20.102): Comfort, Standby, Economy, Building Protection. Cascade regulation according to priorities.
PWM
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.
Lighting
2 termsConstant light control
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.
Scene
Predefined configuration of multiple actuators (lighting, blinds, HVAC, audio) triggered by a single telegram (DPT 17.001 or 18.001). Numbered 0-63.