medium KNX Basic exam questions
KNX Basic Certification mock exam questions selected at medium level. Ideal for consolidating what you've learned and gauging your real level.
Medium level questions
Q01
What is the maximum number of lines that a KNX TP area may contain?- A.12
- B.15
- C.16
- D.32
2. TP Topology· Bereichsgrenzen· MediumCorrect answerB — 15Learning tipA KNX TP area may contain up to 15 subordinate lines, each connected to the area's main line through its own line coupler. Choice A (12) is simply too low. Choice C (16) is the classical trap: it confuses the count of subordinate lines with the total when the main line itself is included. Choice D (32) corresponds to no defined KNX topology limit.
Q02
A KNX TP line can accommodate up to 256 devices when line repeaters are used.TrueFalse2. TP Topology· Liniengrenzen· MediumQ03
Within a KNX area, the maximum number of Line Couplers is 15, one per subsidiary line.TrueFalse2. TP Topology· Bereichsbegrenzungen· MediumCorrect answerTrueLearning tipTrue. A KNX area is built around one main line that connects up to 15 subsidiary lines, each attached to the main line through its own Line Coupler. The limit of 15 follows directly from the topology addressing scheme, which reserves 4 bits for the line identifier within an area. Each subsidiary line itself can then host up to 64 devices (or 256 with additional line segments and segment repeaters).
Q04
Among the following Group Object flags, which one must be enabled so that the device transmits a telegram whenever the object's value changes?- A.Flag C (Communication)
- B.Flag T (Transmit)
- C.Flag W (Write)
- D.Flag U (Update)
3. Bus Devices· Gruppenobjekt-Flags· MediumCorrect answerB — Flag T (Transmit)Learning tipThe T (Transmit) flag enables spontaneous transmission of a telegram whenever the local value of the Group Object changes. C is a prerequisite that enables communication overall but does not by itself trigger sending. W allows receiving write requests from the bus. U handles updating the local value upon receipt of a Group Value Response telegram. Without T, the device can receive values but never sends its own.
Source: Porto KNX — Bus Devices, FlagsQ05
DPT 1.001 (Switch) and DPT 1.008 (UpDown) have the same bit length and the same binary structure; only their semantic meaning differs.TrueFalse3. Bus Devices· DPT (Datapoint Types)· MediumCorrect answerTrueLearning tipBoth DPTs belong to the 1.xxx family, which is encoded on a single bit (boolean). DPT 1.001 = Switch (on/off for general switching), DPT 1.008 = UpDown (up/down for shutters and blinds). The semantic distinction allows ETS to display the appropriate labels and icons, and lets applications behave consistently with the user's expectations.
Q06
KNX RF Multi is newer than KNX RF Ready and uses several frequency channels to improve the robustness of the communication.TrueFalse4. KNX RF· RF Ready vs. RF Multi· MediumCorrect answerTrueLearning tipKNX RF Multi (multi-channel) is the currently recommended generation. It uses several channels within the 868 MHz band together with a fast retry mechanism to keep transmission reliable in noisy environments. KNX RF Ready (the older single-channel generation) was more sensitive to interference and is gradually being phased out in new product designs.
Q07
A bus termination (end-of-line resistor) must be installed at each end of a KNX TP segment, in the same way as for an RS-485 bus.TrueFalse5. TP Installation· Verkabelung· MediumCorrect answerFalseLearning tipFalse. KNX TP does not use any bus termination, which is one of its major differences from other differential buses such as RS-485 or CAN. As a result the physical topology can freely combine line, star and tree shapes without termination constraints. Only the closed-loop (ring) topology is forbidden.
Source: Porto KNX — TP InstallationQ08
ETS Lite is limited to 20 devices per project, whereas ETS Professional has no such limit.TrueFalse6. ETS Project Design· ETS-Versionen· MediumCorrect answerTrueLearning tipETS6 Lite is capped at 20 devices per project, which is enough for an apartment or small house. ETS6 Professional has no practical device limit and is the standard tool for commercial or larger residential projects. ETS6 Inside (older positioning) targeted simple self-installation scenarios. The 12.5% voucher granted after passing the Basic exam applies to ETS Professional.
Source: KNX Association — ETS overviewQ09
The physical programming button on a device must be pressed before every parameter download.TrueFalse7. ETS Programming· Programmiertaste· MediumCorrect answerFalseLearning tipFalse. The programming button only needs to be pressed for the first download of the Individual Address (Individual Address Download), so that the device accepts its new address. Once addressed, all subsequent downloads (parameters, application program) take place without pressing the button, because ETS reaches the device directly through its individual address.
Q10
After a minor parameter change in ETS, which type of download is typically used to minimise the time spent on the bus?- A.Full download (parameters + application)
- B.Partial download (delta only)
- C.Unload (clear the device first)
- D.Reset to factory defaults
7. ETS Programming· Download-Arten· MediumCorrect answerB — Partial download (delta only)Learning tipA Partial download only writes the parameters that have changed since the last download, which is much faster than a Full download (which rewrites the entire configuration). ETS automatically chooses between the two depending on the scale of the changes, but the mode can be forced if needed. Choice C (Unload) is used to wipe a device before reusing it elsewhere — it is destructive. Choice D (factory reset) is even more drastic and unrelated to a routine parameter tweak.
Q11
The 'Reset Device' command in ETS performs a software restart of a KNX device without erasing its individual address or its application configuration.TrueFalse7. ETS Programming· Geräte-Reset· MediumCorrect answerTrueLearning tipReset Device = warm restart: the device loses its runtime state (RAM), reinitialises its timers, Cyclic Send and counters, but preserves its individual address, application program, ETS parameters, and Group Address to Group Object bindings. It is useful to force the re-emission of initial values (cyclic send after a crash), to test a specific power-up behaviour, or to unstick a device frozen in an inconsistent state without having to reload the configuration. Not to be confused with Unload All (full decommissioning) or with simply switching off mains power.
Q12
A single Group Object can be associated simultaneously with several Group Addresses in ETS, which is typically used so that an actuator reacts to several commands (e.g. individual command + zone command + scene).TrueFalse7. ETS Programming· Multi-Binding· MediumCorrect answerTrueLearning tipMulti-binding is a fundamental KNX pattern. Concrete examples: a lighting circuit that reacts to its local switch, to an 'all off' corridor command and to a 'leave for work' scene; a roller shutter that reacts to its local button, to a zone master and to a safety scenario (automatic close on storm warning). The actuator has a single Switch Control Group Object bound to 3-4 different Group Addresses (Lighting_Local_LivingRoom, Lighting_All_Off, Scene_Departure). All these addresses can write into the Group Object; only one (the sending address) is used when emitting status.
Q13
The ETS Bus Monitor displays telegrams at the raw frame level, whereas the Group Monitor presents them filtered and formatted at the Group Address level.TrueFalse8. Diagnostics· Monitoring-Werkzeuge· MediumCorrect answerTrueLearning tipThis is exactly the distinction. Bus Monitor gives a raw, low-level view of every frame on the bus, useful for diagnosing low-level issues such as missing ACKs, parity errors or unexpected source individual addresses. Group Monitor gives a higher-level, business-oriented view in which values are decoded per DPT for each Group Address, ideal for verifying that pressing a button actually sends the expected telegram.
Source: Porto KNX — DiagnosticsQ14
KNX Data Secure encrypts telegrams at the application layer (Group Object), whereas KNX IP Secure encrypts at the transport layer (between IP Routers).TrueFalse9. KNX Secure· Data Secure vs. IP Secure· MediumCorrect answerTrueLearning tipThe key distinction: Data Secure provides encryption and authentication at the application layer, end-to-end between devices, protecting the value of a Group Object regardless of the medium in between. IP Secure provides encryption at the IP transport layer, between IP Routers or via tunnelling, protecting the IP traffic but remaining transparent for the TP devices downstream. Both mechanisms can coexist in the same installation and are commonly deployed together.
Source: KNX Position Paper — KNX SecureQ15
A standard KNX device that is fully programmed contains an Individual Address, an application, parameters and the Group Addresses.TrueFalse1. System Overview· Offizielle Musterprüfung 3· MediumCorrect answerTrueLearning tipTrue. After a successful complete download from ETS, a standard KNX device stores four things: its Individual Address (unique identifier on the topology), its application program (the firmware-level logic for its function), its parameter values (the configuration choices made in ETS), and the list of Group Addresses linked to its Group Objects (the communication side). Only with all four does the device participate correctly in the installation.
Q16
The programming button on a KNX product or the BCU has to be pressed to allocate the Group Addresses during the commissioning stage.TrueFalse7. ETS Programming· Offizielle Musterprüfung 4· MediumCorrect answerFalseLearning tipFalse. The programming button puts the device into 'programming mode' so that ETS can write its Individual Address (Physical Address), not its Group Addresses. Once the Individual Address has been downloaded, the application program and the Group Address links are downloaded over the bus using that Individual Address as the destination, with no further button press required. Confusing the two downloads is one of the most common Basic-exam pitfalls.
Q17
The correct operation of a sensor in a KNX installation can be verified by comparing the filter tables.TrueFalse6. ETS Project Design· Offizielle Musterprüfung 4· MediumCorrect answerFalseLearning tipFalse. Filter tables live in line and area couplers and describe which Group Addresses are allowed to cross the coupler; they say nothing about whether a given sensor actually sends a telegram when stimulated. To verify that a sensor works, the correct tools are the ETS Group Monitor or Bus Monitor, which show in real time the telegrams generated by the sensor and the values carried. Filter-table comparison is a topology/routing check, not a functional sensor check.
Q18
The asymmetric scoring of the KNX Basic exam (+1 for a correct answer, -0.5 for a wrong one, 0 for an abstention) makes it sensible to abstain on questions whose answer is completely unknown rather than to guess at random.TrueFalse10. Exam Meta· Bewertungsschema· MediumCorrect answerTrueLearning tipTrue. With a +1/-0.5/0 scheme, a pure random guess on a True/False question has an expected value of 0.5 x 1 + 0.5 x (-0.5) = +0.25, which looks positive but is highly volatile and easily wiped out by a streak of wrong guesses on borderline items. Abstaining yields a guaranteed 0, which is strictly better than the negative outcome that follows a wrong guess and protects the cumulative score on questions where you have no signal at all. The rule of thumb taught in KNX training centres is: guess when you can eliminate at least one option or when intuition is clearly biased, abstain when the topic is genuinely unknown.