System Overview: KNX Basic exam questions with worked answers

Practice questions from the System Overview block of the KNX Basic certification. Detailed corrections, public sources, free to read without sign-up.

48 questions~ 43 minFree · no sign-up

Questions for the "System Overview" topic

Q01
In KNX there are two types of addressing: individual addressing and group addressing.
TrueFalse
System Overview· Individual & group addresses· Easy
Correct answer
True
Learning tip
The source opens the Addressing chapter by stating there are two types: individual addressing and group addressing.
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Q02
What is the valid value range of the bus-device field in a KNX individual address?
- A.0 to 255
- B.0 to 15
- C.0 to 31
- D.1 to 255
System Overview· Individual & group addresses· Medium
▸
Correct answer
A — 0 to 255
Learning tip
Correct: The bus-device field of an individual address ranges from 0 to 255.
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Q03
How many bits make up the individual address within a KNX telegram?
- A.8 bits
- B.16 bits
- C.32 bits
- D.24 bits
System Overview· Individual & group addresses· Medium
▸
Correct answer
B — 16 bits
Learning tip
Correct: The individual address has a fixed structure of 16 bits.
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Q04
An individual address shall be unique within a KNX installation.
TrueFalse
System Overview· Individual & group addresses· Easy
Correct answer
True
Learning tip
The source states an individual address shall be unique within a KNX installation.
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Q05
What is the primary purpose of the individual address?
- A.To carry everyday switching commands such as light on/off
- B.To link the group objects of several devices for one function
- C.To forward programming telegrams and new application/parameter data via ETS to the bus device
- D.To supply operating power to the bus device
System Overview· Individual & group addresses· Medium
▸
Correct answer
C — To forward programming telegrams and new application/parameter data via ETS to the bus device
Learning tip
Correct: The source states this is the primary goal of the individual address.
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Q06
Once commissioning (with all customisation and diagnostics) is complete, how is normal communication such as light on/off carried out?
- A.Exclusively via individual addresses
- B.Via the broadcast address 0/0/0
- C.Via both individual and group addresses equally
- D.Exclusively via group addresses
System Overview· Individual & group addresses· Medium
▸
Correct answer
D — Exclusively via group addresses
Learning tip
Correct: After commissioning, communication is done exclusively via group addresses.
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Q07
In the classic first-assignment procedure using the programming button (without a serial number), when can the individual address be downloaded?
- A.Only as long as the programming LED is lit
- B.At any time during normal operation
- C.Only after the device has been powered off
- D.Only via a group address telegram
System Overview· Individual & group addresses· Medium
▸
Correct answer
A — Only as long as the programming LED is lit
Learning tip
In the classic button-based assignment procedure, the programming LED identifies the device. ETS can also overwrite a known address without physically pressing the button, or assign an address by serial number on compatible devices. These exceptions do not allow arbitrary writing "at any time".
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Q08
Normal communication between devices in a KNX installation is carried out via group addresses.
TrueFalse
System Overview· Individual & group addresses· Easy
Correct answer
True
Learning tip
The source states normal communication between devices is carried out via group addresses.
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Q09
What is the group address 0/0/0 reserved for?
- A.The first lighting circuit in the building
- B.Broadcast, required for assigning and establishing individual addresses
- C.Central switching of all actuators
- D.Indicating the programming LED state
System Overview· Individual & group addresses· Medium
▸
Correct answer
B — Broadcast, required for assigning and establishing individual addresses
Learning tip
Correct: 0/0/0 is reserved as the broadcast address, used when assigning individual addresses.
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Q10
Which three group address representations can be selected for an ETS project?
- A.1-level, 2-level and 3-level numeric
- B.Area/Line/Device, Main/Sub and free
- C.3-level (main/middle/sub), 2-level (main/sub) and a freely defined structure
- D.Decimal, hexadecimal and binary
System Overview· Individual & group addresses· Medium
▸
Correct answer
C — 3-level (main/middle/sub), 2-level (main/sub) and a freely defined structure
Learning tip
Correct: The source lists these three representation options.
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Q11
Which group address representation is the default in ETS?
- A.The 2-level structure
- B.The free structure
- C.There is no default; one must always choose manually
- D.The 3-level structure
System Overview· Individual & group addresses· Easy
▸
Correct answer
D — The 3-level structure
Learning tip
Correct: The default level structure in ETS is the 3-level structure.
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Q12
In the 3-level group address structure, what are the value ranges of main / middle / sub?
- A.Main 0-31, Middle 0-7, Sub 0-255
- B.Main 0-15, Middle 0-15, Sub 0-255
- C.Main 0-31, Middle 0-255, Sub 0-7
- D.Main 0-7, Middle 0-31, Sub 0-2047
System Overview· Individual & group addresses· Medium
▸
Correct answer
A — Main 0-31, Middle 0-7, Sub 0-255
Learning tip
Correct: The 3-level structure uses main 0-31, middle 0-7, sub 0-255.
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Q13
In the 2-level group address structure, what are the ranges of main / sub?
- A.Main 0-31, Sub 0-255
- B.Main 0-31, Sub 0-2047
- C.Main 0-15, Sub 0-2047
- D.Main 0-2047, Sub 0-31
System Overview· Individual & group addresses· Medium
▸
Correct answer
B — Main 0-31, Sub 0-2047
Learning tip
Correct: The 2-level structure uses main 0-31 and sub 0-2047.
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Q14
What is the value range of a freely structured (free) group address?
- A.0 to 65535
- B.1 to 32767
- C.1 to 65535
- D.0 to 2047
System Overview· Individual & group addresses· Medium
▸
Correct answer
C — 1 to 65535
Learning tip
Correct: The free structure allows values 1 to 65535.
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Q15
How many group addresses are available in total from ETS4 onwards?
- A.32767
- B.65536
- C.255
- D.65535
System Overview· Individual & group addresses· Medium
▸
Correct answer
D — 65535
Learning tip
Correct: From ETS4 onwards 65535 group addresses are available.
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Q16
Within a bus device, to what are group addresses assigned?
- A.To the group objects of the device
- B.To the individual address of the device
- C.To the programming LED
- D.To the choke of the power supply
System Overview· Individual & group addresses· Medium
▸
Correct answer
A — To the group objects of the device
Learning tip
Correct: Group addresses are assigned to the group objects of the respective bus devices.
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Q17
According to the three-level convention presented in this course, what does the main group represent?
- A.The functional domain (lighting, heating, ...)
- B.The floor number
- C.The individual load
- D.The area of the topology
System Overview· Individual & group addresses· Medium
▸
Correct answer
B — The floor number
Learning tip
Correct: In the common convention the main group is the floor number. This project convention is not imposed by the KNX protocol; other consistent organisations, including by function, are possible.
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Q18
In KNX TP, which logical state is represented by current being drawn (signal voltage present) on the line?
- A.Logical 0
- B.Logical 1
- C.Neither state draws current; both are coded purely by a voltage level
- D.Both 0 and 1 draw the same current
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
A — Logical 0
Learning tip
Correct: During logical state 0 there is signal voltage and current is drawn on the line.
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Q19
If several KNX TP devices transmit at the same time, which logical state prevails on the bus?
- A.Logical 1, because 1 is the idle state
- B.Logical 0, because a 0 draws current and overrides a 1
- C.Whichever device began transmitting first
- D.Neither, because both telegrams are corrupted
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
B — Logical 0, because a 0 draws current and overrides a 1
Learning tip
Correct: A 0 draws current on the line, so if any device sends a 0 the bus shows 0 and the 0 prevails.
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Q20
How is bus access organised in KNX TP?
- A.A central master polls each device in turn
- B.A token is passed between devices in a fixed order
- C.Decentralised: there is no central master/slave controller and each device accesses the bus itself
- D.The power supply assigns each device a fixed time slot
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
C — Decentralised: there is no central master/slave controller and each device accesses the bus itself
Learning tip
Correct: KNX TP bus access is not controlled centrally by a master/slave scheme; devices access the bus on their own.
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Q21
What does the abbreviation CSMA/CA stand for in KNX TP bus access?
- A.Carrier Sense Multiple Access with Collision Detection
- B.Central Signal Management with Automatic arbitration
- C.Cyclic Slot Multiple Access with Contention Avoidance
- D.Carrier Sense Multiple Access with Collision Avoidance
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
D — Carrier Sense Multiple Access with Collision Avoidance
Learning tip
Correct: CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance.
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Q22
During transmission, when does a KNX TP bus device listen to the bus?
- A.While transmitting, as long as it is not itself sending a logical 0
- B.Only before it starts transmitting, never during
- C.Only after the whole telegram has been sent
- D.Never, because a transmitting device cannot receive at the same time
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
A — While transmitting, as long as it is not itself sending a logical 0
Learning tip
Correct: Bus devices listen to the bus while transmitting, except when they are themselves sending a logical 0.
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Q23
After a KNX TP device stops transmitting because another device is sending a 0, what does it do next?
- A.It discards its telegram and never retries
- B.It immediately resends on top of the ongoing telegram
- C.It keeps listening until the current telegram ends, evaluates it, then tries to send its own telegram again
- D.It waits for a central master to grant it access again
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
C — It keeps listening until the current telegram ends, evaluates it, then tries to send its own telegram again
Learning tip
Correct: The device that stopped continues to listen to the end of the telegram, evaluates it, and attempts to send again.
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Q24
What is the effect of CSMA/CA collision handling on data throughput in KNX TP?
- A.Throughput halves whenever two devices collide
- B.All colliding telegrams are lost and resent, lowering throughput
- C.Throughput drops to zero until a master resets the bus
- D.Throughput is not reduced, because the winning telegram completes without data loss
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
D — Throughput is not reduced, because the winning telegram completes without data loss
Learning tip
Correct: Since one telegram continues uninterrupted and none is destroyed, data throughput is not reduced.
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Q25
A KNX TP device has a telegram ready, but a higher-priority telegram is currently on the bus. What happens?
- A.It waits until the higher-priority telegram has finished, then tries to send again
- B.It sends anyway, so the two telegrams mix on the bus
- C.The higher-priority telegram is aborted so the waiting device can send
- D.It discards its telegram permanently
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
A — It waits until the higher-priority telegram has finished, then tries to send again
Learning tip
Correct: A device blocked by a higher-priority telegram waits for it to finish and then retries.
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Q26
In KNX symmetrical transmission, how are the two signal wires referenced to potential?
- A.One wire carries the signal and the other is connected to PE (ground)
- B.Neither wire is connected to ground/PE or to any fixed potential
- C.Both wires are tied to a fixed reference potential
- D.The black wire is grounded and the red wire carries the signal
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
B — Neither wire is connected to ground/PE or to any fixed potential
Learning tip
Correct: The source states neither wire is connected to ground/PE nor to a fixed potential.
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Q27
What does a KNX TP bus device actually evaluate on the wire pair?
- A.The absolute voltage of each wire measured against ground
- B.The DC supply voltage level only
- C.Only the difference of the AC voltage between the two wires
- D.The sum of the voltages on both wires
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
C — Only the difference of the AC voltage between the two wires
Learning tip
Correct: The bus device evaluates only the difference of the AC voltage between the two wires.
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Q28
Why does radiated external noise not disturb the KNX signal in symmetrical transmission?
- A.The device filters out all AC and keeps only the DC
- B.A shield connected to PE absorbs the noise before it reaches the wires
- C.The noise is always at a different frequency and is simply ignored
- D.Because the noise hits both wires with the same polarity, it does not change the voltage difference the device evaluates
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
D — Because the noise hits both wires with the same polarity, it does not change the voltage difference the device evaluates
Learning tip
Correct: Radiated noise affects both wires with the same polarity and so has no effect on the evaluated difference.
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Q29
How are data and supply carried on the KNX TP bus pair?
- A.The AC data voltage is superimposed onto the DC supply voltage on the same pair
- B.Data uses one wire pair and the DC supply uses a separate pair
- C.The supply is an AC voltage and the data is a DC voltage
- D.Data and supply take turns in time on the same wires
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
A — The AC data voltage is superimposed onto the DC supply voltage on the same pair
Learning tip
Correct: The AC data is superimposed onto the DC supply voltage on the same wire pair.
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Q30
Which component in a KNX bus device separates the DC supply voltage from the AC information (data) voltage?
- A.A shield connected to protective earth
- B.The transformer-IC
- C.A choke located inside each bus device
- D.The application interface
System Overview· Bus access & signal transmission· Medium
▸
Correct answer
B — The transformer-IC
Learning tip
Correct: The transformer-IC in the bus device separates the DC supply voltage from the AC information voltage.
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Q31
When does an S-mode KNX installation become ready for operation?
- A.As soon as the devices are mechanically mounted and the bus voltage is present.
- B.Immediately, because S-mode application programs are pre-installed at the factory.
- C.After the sensors and actuators have been downloaded with their application program via ETS.
- D.Once individual addresses are assigned, even if no application program is loaded yet.
System Overview· Configuration modes & group objects· Medium
▸
Correct answer
C — After the sensors and actuators have been downloaded with their application program via ETS.
Learning tip
Correct: the source states an S-mode installation is not ready until sensors and actuators are downloaded with the application program via ETS.
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Q32
In the ETS configuration steps, group addresses are assigned in order to logically connect sensors and actuators and thereby realise the desired functions.
TrueFalse
System Overview· Configuration modes & group objects· Easy
Correct answer
True
Learning tip
The source lists 'assigning group addresses in order to logically connect sensors and actuators and by doing so realize the desired functions' as an ETS configuration step.
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Q33
Which of the following is NOT one of the ETS configuration steps for S-mode products?
- A.Assigning individual addresses to the devices.
- B.Selecting the appropriate application programs for the bus devices.
- C.Setting the parameters for the bus devices.
- D.Mechanically mounting the bus devices on the rail.
System Overview· Configuration modes & group objects· Medium
▸
Correct answer
D — Mechanically mounting the bus devices on the rail.
Learning tip
Correct: mounting the devices is done beforehand ('after mounting the devices'); it is not one of the ETS configuration steps, which are: assign individual addresses, select application programs, set parameters and assign group addresses.
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Q34
Using group addresses in ETS, which group objects may be linked together?
- A.Any two group objects, regardless of their size.
- B.Only group objects that have the same size.
- C.Only group objects located in the same bus device.
- D.Only group objects that are exactly 1 bit in size.
System Overview· Configuration modes & group objects· Medium
▸
Correct answer
B — Only group objects that have the same size.
Learning tip
Correct: the source states ETS only allows linking group objects that have the same size.
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Q35
Which set of components makes up a minimum KNX TP installation?
- A.A power supply, a line coupler, a sensor and an actuator
- B.Only a sensor and an actuator wired directly to 230 V
- C.A KNX power supply unit (30 V DC)/choke, one sensor, one actuator and the bus cable
- D.A power supply, a router, a gateway and several actuators
System Overview· Definition & minimal TP installation· Medium
▸
Correct answer
C — A KNX power supply unit (30 V DC)/choke, one sensor, one actuator and the bus cable
Learning tip
Correct: The source lists exactly these four elements for a minimum TP installation.
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Q36
What is the output voltage of the KNX power supply unit in a minimal TP installation?
- A.24 V DC
- B.230 V AC
- C.12 V DC
- D.30 V DC
System Overview· Definition & minimal TP installation· Easy
▸
Correct answer
D — 30 V DC
Learning tip
Correct: The KNX power supply unit outputs 30 V DC onto the TP bus.
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Q37
How many wires of the KNX bus cable are required to transmit telegrams and (in most cases) power the bus device?
- A.Two
- B.Four
- C.One
- D.Three
System Overview· Definition & minimal TP installation· Easy
▸
Correct answer
A — Two
Learning tip
Correct: Only two wires are required for telegram transmission and, in most cases, for supplying the device.
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Q38
What additional role can the spare wire pair of the KNX bus cable serve?
- A.Carrying 230 V mains to the actuators
- B.Providing ancillary (additional) power to bus devices
- C.Doubling the telegram transmission speed
- D.Acting as a protective earth
System Overview· Definition & minimal TP installation· Medium
▸
Correct answer
B — Providing ancillary (additional) power to bus devices
Learning tip
Correct: The source states the spare wire pair can provide ancillary power to bus devices.
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Q39
Apart from the 4-bit relative dimming object, which objects does the Dimming functional block consist of at least?
- A.Two shutter objects (DPT_Step 1.007 and DPT_UpDown 1.008).
- B.A temperature object (9.001) and a lux object (9.004).
- C.Only a single 1-bit switching object (DPT_Switch 1.001).
- D.A switching object (DPT_Switch 1.001) and a value object (DPT_Scaling 5.001).
System Overview· TP telegram data & datapoint types· Medium
▸
Correct answer
D — A switching object (DPT_Switch 1.001) and a value object (DPT_Scaling 5.001).
Learning tip
Correct: besides DPT_Control_Dimming (3.007), the dimming block has at least a switching object (1.001) and a value object (5.001).
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Q40
Which datapoint type does a typical dimming actuator support in addition to those supported by the dimming sensor?
- A.DPT_Scaling (5.001)
- B.DPT_Control_Dimming (3.007)
- C.DPT_Switch (1.001)
- D.DPT_UpDown (1.008)
System Overview· TP telegram data & datapoint types· Medium
▸
Correct answer
A — DPT_Scaling (5.001)
Learning tip
Correct: a typical dimming actuator additionally supports DPT_Scaling (5.001) for absolute brightness values.
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Q41
Which datapoint ID and name are correctly matched?
- A.1.001 - DPT_Step
- B.3.007 - DPT_Switch
- C.9.004 - DPT_Value_Temp
- D.5.001 - DPT_Scaling
System Overview· TP telegram data & datapoint types· Medium
▸
Correct answer
D — 5.001 - DPT_Scaling
Learning tip
Correct: 5.001 is DPT_Scaling, the 1-byte absolute value (scaling) object.
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Q42
What can occur if the maximum total bus length in a TP line segment is exceeded?
- A.The bus voltage rises above 30 V
- B.The choke is destroyed
- C.Nothing, because there is a built-in safety margin
- D.Irreproducible data transmission problems
System Overview· Power supply & cable lengths· Medium
▸
Correct answer
D — Irreproducible data transmission problems
Learning tip
Correct: The text states that irreproducible data transmission problems can occur.
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Q43
What does the TP power supply unit constantly deliver?
- A.30 V DC
- B.24 V DC
- C.30 V AC
- D.12 V DC
System Overview· Power supply & cable lengths· Easy
▸
Correct answer
A — 30 V DC
Learning tip
Correct: The power supply delivers constantly 30 V DC.
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Q44
Why is a choke placed between the power supply and the bus line?
- A.To increase the bus voltage from 24 V to 30 V
- B.To stop the power supply's voltage regulator from correcting (cancelling) the AC information voltage
- C.To convert the 30 V DC into AC for the devices
- D.To protect the devices against short circuits
System Overview· Power supply & cable lengths· Medium
▸
Correct answer
B — To stop the power supply's voltage regulator from correcting (cancelling) the AC information voltage
Learning tip
Correct: Without the choke the regulator would try to correct the AC information voltage, causing a tug of war with the sending device.
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Q45
Which half of the AC voltage pulse is generated by the choke?
- A.The first (negative) half
- B.Both halves
- C.The second (positive) half
- D.Neither; the sending bus device generates the whole pulse
System Overview· Power supply & cable lengths· Medium
▸
Correct answer
C — The second (positive) half
Learning tip
Correct: The choke generates the second (positive) half of the pulse.
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Q46
Why may bus devices only be installed up to 350 m from the choke (power supply unit)?
- A.Because beyond 350 m the 30 V DC supply drops to zero
- B.Because collisions cannot be resolved beyond 350 m
- C.Because ETS cannot address devices further than 350 m away
- D.Because the choke plays a significant role in forming the equalization pulse
System Overview· Power supply & cable lengths· Medium
▸
Correct answer
D — Because the choke plays a significant role in forming the equalization pulse
Learning tip
Correct: The choke helps form the positive equalization pulse, so devices must stay within 350 m of it.
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Q47
Which effects make it necessary to limit the total cable length per line segment to 1000 m?
- A.Signal damping and edge-rounding by the cable capacity, plus a signal-level drop from the resistive load
- B.Overheating of the choke and the voltage regulator
- C.Loss of the 30 V DC supply beyond 1000 m
- D.ETS addressing limits
System Overview· Power supply & cable lengths· Medium
▸
Correct answer
A — Signal damping and edge-rounding by the cable capacity, plus a signal-level drop from the resistive load
Learning tip
Correct: These two effects degrade the signal, so the segment is limited to 1000 m.
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Q48
What does the maximum number of devices per TP line segment depend on?
- A.Always exactly 64 devices, regardless of consumption
- B.The total power consumption of the devices
- C.The total cable length only
- D.The number of power supply units only
System Overview· Power supply & cable lengths· Medium
▸
Correct answer
B — The total power consumption of the devices
Learning tip
Correct: The maximum number of devices per segment depends on their total power consumption.
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