KNX Topology: KNX Basic exam questions with worked answers

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

53 questions~ 48 minFree · no sign-up

Questions for the "KNX Topology" topic

Q01
For a building planned and commissioned from 2019, what is the ideal maximum number of bus devices per floor?
- A.256
- B.64
- C.255
- D.128
KNX Topology· Building structure, backbone & interfaces· Medium
▸
Correct answer
A — 256
Learning tip
Correct: From 2019 an ideal installation has no more than 256 bus devices per floor.
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Q02
Which pairing of date range and ideal bus devices per floor is correct?
- A.Prior to 2018: 256 per floor; from 2019: 64 per floor.
- B.Prior to 2018: 64 per floor; from 2019: 256 per floor.
- C.Prior to 2018: 64 per floor; from 2019: 128 per floor.
- D.Prior to 2018: 255 per floor; from 2019: 255 per floor.
KNX Topology· Building structure, backbone & interfaces· Medium
▸
Correct answer
B — Prior to 2018: 64 per floor; from 2019: 256 per floor.
Learning tip
Correct: The ideal figures are 64 per floor prior to 2018 and 256 per floor from 2019.
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Q03
How is faster line-crossing communication achieved when adapting a KNX topology to IP?
- A.Every TP device is replaced by an IP device.
- B.The IP network takes the place of the main/backbone lines, replacing line- and backbone couplers with KNXnet/IP routers.
- C.The TP line speed is increased above 9,600 bit/s.
- D.Line couplers are removed entirely and no filtering is done.
KNX Topology· Building structure, backbone & interfaces· Medium
▸
Correct answer
B — The IP network takes the place of the main/backbone lines, replacing line- and backbone couplers with KNXnet/IP routers.
Learning tip
Correct: IP replaces the main/backbone line level and KNXnet/IP routers replace the line/backbone couplers.
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Q04
Using Gigabit switches, how much faster can data be transmitted for line-crossing communication compared with a TP main/backbone line?
- A.About 1,000 times faster.
- B.About 100 times faster.
- C.About 100,000 times faster.
- D.About 10 times faster.
KNX Topology· Building structure, backbone & interfaces· Medium
▸
Correct answer
C — About 100,000 times faster.
Learning tip
Correct: The source states data can be transmitted 100,000 times faster with Gigabit switches.
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Q05
Which IP communication method is commonly used by ETS for programming over IP?
- A.Routing.
- B.Multicast broadcasting only.
- C.A serial interface connection.
- D.Tunneling.
KNX Topology· Building structure, backbone & interfaces· Medium
▸
Correct answer
D — Tunneling.
Learning tip
Correct: Tunneling is the standardized method commonly used by ETS for programming over IP.
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Q06
What does a coupler's filter table contain?
- A.The individual addresses of all devices on the secondary line.
- B.Every group address used anywhere in the installation.
- C.The routing counter values for each telegram.
- D.The active line-crossing group addresses (linked to devices on both sides of the coupler).
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
D — The active line-crossing group addresses (linked to devices on both sides of the coupler).
Learning tip
Correct: the filter table contains the active line-crossing group addresses, i.e. all group addresses linked to bus devices on both sides of the coupler.
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Q07
Which telegrams does a line or backbone coupler forward across the lines it connects?
- A.Only line-crossing telegrams whose group address is in its filter table.
- B.All telegrams it receives, unchanged.
- C.Only telegrams sent to individual addresses.
- D.None - a coupler only galvanically isolates the lines.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
A — Only line-crossing telegrams whose group address is in its filter table.
Learning tip
Correct: couplers route only line-crossing telegrams, i.e. those whose group address is in the filter table; each line works independently.
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Q08
How does a line repeater differ from a line coupler in the way it handles telegrams?
- A.The repeater filters telegrams using a larger filter table.
- B.The repeater has no filter table and passes on all telegrams.
- C.The repeater routes only individually addressed telegrams.
- D.The repeater blocks all telegrams to isolate the segment.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
B — The repeater has no filter table and passes on all telegrams.
Learning tip
Correct: the line repeater has no filter table and therefore passes on all telegrams, unlike a coupler which forwards only line-crossing telegrams.
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Q09
What is the advantage of supplying a coupler from the primary line rather than the secondary line?
- A.It doubles the number of devices allowed on the secondary line.
- B.It removes the need for a choke on the secondary line.
- C.The coupler can report a power failure of the secondary line.
- D.It lets the coupler work without a controller.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
C — The coupler can report a power failure of the secondary line.
Learning tip
Correct: if supplied by the primary line, the coupler can report a secondary line power failure.
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Q10
What determines whether a coupler acts as a backbone coupler, a line coupler or a line repeater?
- A.Three different hardware models are used, one per role.
- B.The number of devices connected to the secondary line.
- C.A hardware switch on the coupler set during installation.
- D.Its location and the assigned individual address.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
D — Its location and the assigned individual address.
Learning tip
Correct: the couplers are identical devices whose task depends on the location and the corresponding assigned individual address.
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Q11
Between which two lines does a backbone coupler (BC) provide the connection?
- A.Between the backbone line and a main line.
- B.Between two secondary lines.
- C.Between a main line and a secondary line.
- D.Between a line segment and the next line segment.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
A — Between the backbone line and a main line.
Learning tip
Correct: the backbone coupler BC provides the connection between the backbone line and the main line.
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Q12
A line coupler (LC) is used to connect which two lines?
- A.The backbone line and a main line.
- B.A main line and a secondary line.
- C.Two line segments of the same line.
- D.The backbone line and a secondary line directly.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
B — A main line and a secondary line.
Learning tip
Correct: the line coupler LC connects the main line and a secondary line.
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Q13
By how many line segments can a line repeater extend a line, at most?
- A.1 line segment
- B.15 line segments
- C.3 line segments
- D.4 line segments
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
C — 3 line segments
Learning tip
Correct: a line repeater extends a line by a maximum of 3 line segments.
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Q14
What does a line coupler do with the data communication between the main line and its secondary line?
- A.It forwards all telegrams in both directions.
- B.It monitors the communication both ways and routes only telegrams whose group addresses are in its filter table.
- C.It blocks all traffic between the two lines.
- D.It converts individual addresses into group addresses.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
B — It monitors the communication both ways and routes only telegrams whose group addresses are in its filter table.
Learning tip
Correct: the line coupler monitors data communication between the main line and the secondary line and vice versa, routing only telegrams whose group addresses are stored in its filter table.
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Q15
In an installation with several lines, how is power supplied to the lines?
- A.One central power supply feeds all lines through the couplers.
- B.Only the main line needs a power supply; secondary lines draw from it.
- C.Each line and each line segment has its own power supply unit and choke.
- D.A power supply is needed per area, shared by its lines.
KNX Topology· Couplers: function, block diagram & application· Medium
▸
Correct answer
C — Each line and each line segment has its own power supply unit and choke.
Learning tip
Correct: each line and each line segment must have its own power supply unit and choke.
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Q16
The individual address serves to clearly identify a bus device and describes its location within the topology.
TrueFalse
KNX Topology· Individual address structure in the topology· Easy
Correct answer
True
Learning tip
Correct. The individual address serves to clearly identify the bus device and describes its location within the topology.
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Q17
The individual address is structured in the order Line.Area.Device (for example 1.1.5).
TrueFalse
KNX Topology· Individual address structure in the topology· Easy
Correct answer
False
Learning tip
False. The individual address is structured Area.Line.Device (A.L.B), e.g. 1.1.5 = area 1, line 1, device 5 - not Line.Area.Device.
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Q18
In the individual address, the area field A can address the areas 1 to 16.
TrueFalse
KNX Topology· Individual address structure in the topology· Easy
Correct answer
False
Learning tip
False. A = 1...15 addresses the areas 1 to 15 (at most 15 areas). A = 0 addresses the bus devices on the backbone line.
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Q19
What does the value L = 0 address in a KNX individual address?
- A.The first bus device of the line.
- B.The backbone line of the installation.
- C.The main line of the respective area.
- D.The line coupler of the line.
KNX Topology· Individual address structure in the topology· Medium
▸
Correct answer
C — The main line of the respective area.
Learning tip
Correct: L = 0 addresses the main line of the respective area.
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Q20
The device field B can address bus devices numbered 1 to 256 on a line.
TrueFalse
KNX Topology· Individual address structure in the topology· Easy
Correct answer
False
Learning tip
False. B = 1...255 addresses the bus devices on a line; the maximum device number is 255, not 256. B = 0 addresses the line coupler.
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Q21
A device carries the individual address 1.1.0. What does the device number 0 tell you?
- A.It is the line coupler of that line (x.y.0 addresses the line coupler).
- B.It is the first ordinary bus device on the line.
- C.It is an unloaded device still at its factory default.
- D.It is the backbone coupler of the area.
KNX Topology· Individual address structure in the topology· Medium
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Correct answer
A — It is the line coupler of that line (x.y.0 addresses the line coupler).
Learning tip
Correct: B = 0 addresses the line coupler in the respective line; 1.1.0 is the line coupler of line 1 in area 1.
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Q22
The individual address of an unloaded bus device is 15.15.254.
TrueFalse
KNX Topology· Individual address structure in the topology· Easy
Correct answer
False
Learning tip
False. The individual address of an unloaded bus device is 15.15.255 (the maximum address). New devices are typically delivered ex-factory with 15.15.255.
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Q23
Which coupler role(s) can a KNXnet/IP router take on in a KNX installation?
- A.Only a line repeater inside a single line
- B.Only a backbone coupler
- C.Both a line coupler and a backbone coupler
- D.Only a line coupler
KNX Topology· KNXnet/IP routers & segment coupler· Easy
▸
Correct answer
C — Both a line coupler and a backbone coupler
Learning tip
Correct: the source states the KNXnet/IP router can be used as a line coupler as well as a backbone coupler.
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Q24
In which situation does the high bit rate of the Ethernet backbone NOT prevent problems?
- A.When the routing counter of a telegram reaches zero.
- B.Whenever a line has fewer than 240 devices.
- C.Only when RF segments are present in the installation.
- D.When telegrams are sent out simultaneously from all lines into one single line.
KNX Topology· KNXnet/IP routers & segment coupler· Medium
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Correct answer
D — When telegrams are sent out simultaneously from all lines into one single line.
Learning tip
Correct: the source says Ethernet's higher speed will not help when all lines send telegrams simultaneously into one single line.
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Q25
Before segment couplers, what was the maximum number of small TP islands that could be connected via an IP backbone (the 'hotel scenario')?
- A.240
- B.225
- C.256
- D.255
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
A — 240
Learning tip
Correct: the source gives a maximum of 240 TP islands (225 + 15).
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Q26
Why were segment couplers needed for adding a few RF devices to a TP installation, especially an existing one?
- A.RF devices cannot coexist with TP devices under any circumstances.
- B.RF devices require their own area with its own backbone coupler.
- C.Previously the media coupler had to be installed in the main line, but a single-line installation (e.g. 1.1) has no main line - so a way to branch a TP line off for RF devices was needed.
- D.The routing counter must be reset for RF telegrams.
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
C — Previously the media coupler had to be installed in the main line, but a single-line installation (e.g. 1.1) has no main line - so a way to branch a TP line off for RF devices was needed.
Learning tip
Correct: without a main line (as in a single line 1.1), the old media coupler had nowhere to go, so branching a TP line for RF devices became necessary.
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Q27
Which statement about filtering between the segments of a line is correct?
- A.TP line repeaters filter between segments, so segment couplers were unnecessary.
- B.Neither repeaters nor segment couplers can filter within a line.
- C.Filtering between segments only works over an IP backbone.
- D.Segment couplers introduce filtering between different segments of a line, which does not exist with TP line repeaters.
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
D — Segment couplers introduce filtering between different segments of a line, which does not exist with TP line repeaters.
Learning tip
Correct: providing inter-segment filtering - absent in TP repeaters - was one reason for segment couplers.
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Q28
Into how many subsegments (besides the main segment) can TP line repeaters physically subdivide a line?
- A.Up to three
- B.Any number
- C.Up to seven
- D.Exactly one
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
A — Up to three
Learning tip
Correct: TP repeaters allow a main segment plus up to three subsegments.
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Q29
What is a limitation of TP line repeaters compared with segment couplers?
- A.They filter group addresses but not individual addresses.
- B.They are unaware which device address is in which subsegment and have no filter table, so they forward all traffic.
- C.They can only be used on RF media.
- D.They limit a line to 240 devices.
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
B — They are unaware which device address is in which subsegment and have no filter table, so they forward all traffic.
Learning tip
Correct: repeaters cannot tell where an address lives and have no filter table, so every telegram reaches every segment.
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Q30
From which ETS version was the concept of segment couplers introduced?
- A.ETS4
- B.ETS5
- C.ETS6
- D.ETS3
KNX Topology· KNXnet/IP routers & segment coupler· Easy
▸
Correct answer
C — ETS6
Learning tip
Correct: the concept of segment couplers was introduced in ETS6.
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Q31
How many main segments does a line have when using segment couplers?
- A.Up to three
- B.Any number
- C.One per subsegment
- D.Exactly one
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
D — Exactly one
Learning tip
Correct: each line has exactly one main segment (plus any number of subsegments).
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Q32
Device 1.1.44 is an RF device sitting in an RF subsegment behind a TP-RF segment coupler on a TP main segment. What does this show?
- A.A subsegment may use a different medium (RF) than its main segment (TP).
- B.Individual addresses encode the transmission medium.
- C.An RF device must always have device address 0.
- D.The main segment must also be converted to RF.
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
A — A subsegment may use a different medium (RF) than its main segment (TP).
Learning tip
Correct: subsegments can be a different medium type; an RF subsegment can be coupled to a TP main segment.
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Q33
Regardless of how many subsegments it contains, the maximum number of devices in a single line (including all couplers) is:
- A.240
- B.255
- C.225
- D.256
KNX Topology· KNXnet/IP routers & segment coupler· Medium
▸
Correct answer
D — 256
Learning tip
Correct: a line may hold no more than 256 devices in total, including all couplers.
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Q34
What characterises an internal line telegram?
- A.It is always forwarded onto the main line by the line coupler.
- B.It is a telegram sent with routing counter 7 by a service device.
- C.Sender and destination devices are on the same line, so the telegram is not routed to another line.
- D.It travels via the backbone line to reach devices in other areas.
KNX Topology· Telegram routing & routing counter· Easy
▸
Correct answer
C — Sender and destination devices are on the same line, so the telegram is not routed to another line.
Learning tip
Correct: For an internal line telegram both devices belong to the same line, so the line coupler has no reason to forward it.
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Q35
A telegram is transmitted on a line. Which devices execute the command it carries?
- A.Every device on the line, because all of them receive the telegram.
- B.Only the line coupler of that line.
- C.Only the device that sent the telegram.
- D.Only the devices whose parameters contain the matching group address.
KNX Topology· Telegram routing & routing counter· Medium
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Correct answer
D — Only the devices whose parameters contain the matching group address.
Learning tip
Correct: All devices listen in, but only those with the same group address as the telegram execute the command.
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Q36
What must happen for a telegram to reach a device located on a different line of the same area?
- A.It travels directly from one line to the other without any coupler.
- B.It must be transmitted via the main line, routed by the line couplers of both lines.
- C.It must always be routed over the backbone line.
- D.It must be resent manually because lines cannot exchange telegrams.
KNX Topology· Telegram routing & routing counter· Medium
▸
Correct answer
B — It must be transmitted via the main line, routed by the line couplers of both lines.
Learning tip
Correct: A line-crossing telegram travels up to the main line and back down, routed by the line couplers of the source and destination lines.
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Q37
Why does line coupler LC 2 route the sensor's group telegram 0/2/11 onto the main line?
- A.A line coupler forwards every telegram it receives to the main line.
- B.Because the routing counter had already reached 0.
- C.Its parameterisation (filter table) shows that devices outside line 2 respond to that group address.
- D.Because only line repeaters, not couplers, can forward telegrams.
KNX Topology· Telegram routing & routing counter· Medium
▸
Correct answer
C — Its parameterisation (filter table) shows that devices outside line 2 respond to that group address.
Learning tip
Correct: LC 2 forwards 0/2/11 because its filter table shows external devices need it.
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Q38
How can a device address bus devices located in a different area?
- A.Via the backbone line, which interconnects the areas.
- B.Via the main line only, without the backbone line.
- C.Directly, because all areas share one common line.
- D.It cannot; devices in different areas can never communicate.
KNX Topology· Telegram routing & routing counter· Medium
▸
Correct answer
A — Via the backbone line, which interconnects the areas.
Learning tip
Correct: An area-crossing telegram uses the backbone line to move between areas.
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Q39
What is the initial value of the routing counter in a telegram sent by a normal bus device?
- A.5
- B.7
- C.6
- D.0
KNX Topology· Telegram routing & routing counter· Easy
▸
Correct answer
C — 6
Learning tip
Correct: A telegram starts with a routing counter of 6.
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Q40
Which devices decrement the routing counter of a telegram?
- A.Only backbone couplers, never line couplers or repeaters.
- B.Only the sending device, once, before transmission.
- C.The receiving actuator when it executes the command.
- D.Every line-/backbone coupler and every line repeater that passes the telegram on.
KNX Topology· Telegram routing & routing counter· Medium
▸
Correct answer
D — Every line-/backbone coupler and every line repeater that passes the telegram on.
Learning tip
Correct: Line couplers, backbone couplers and line repeaters each decrement the routing counter when forwarding.
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Q41
In a modern (post-2019, TP-256) installation, what is the maximum number of bus devices that can be mounted in one line segment?
- A.256
- B.64
- C.255
- D.16
KNX Topology· Line segment, line, area & network structure· Easy
▸
Correct answer
A — 256
Learning tip
Correct: the Line segment section states a maximum of 256 devices per line segment.
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Q42
In installations planned and commissioned up to and including 2018, how many TP devices could be mounted in one line segment?
- A.256
- B.64
- C.255
- D.4
KNX Topology· Line segment, line, area & network structure· Easy
▸
Correct answer
B — 64
Learning tip
Correct: up to 2018 only 64 TP devices could be mounted in one line segment.
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Q43
What is the smallest unit in the KNX TP topology?
- A.The line
- B.The single bus device
- C.The line segment
- D.The area
KNX Topology· Line segment, line, area & network structure· Easy
▸
Correct answer
C — The line segment
Learning tip
Correct: the source states the smallest unit in the TP topology is the line segment.
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Q44
At most how many line segments can form a single line?
- A.4
- B.3
- C.15
- D.256
KNX Topology· Line segment, line, area & network structure· Easy
▸
Correct answer
A — 4
Learning tip
Correct: up to 4 line segments form a line.
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Q45
What is the maximum number of line repeaters that may be used to extend one line?
- A.15
- B.3
- C.4
- D.16
KNX Topology· Line segment, line, area & network structure· Easy
▸
Correct answer
B — 3
Learning tip
Correct: a maximum of 3 line repeaters may be used to extend a line.
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Q46
Up to what cable length can 256 devices sit in one line without needing any line repeater?
- A.4000 m
- B.100 m
- C.1000 m
- D.700 m
KNX Topology· Line segment, line, area & network structure· Medium
▸
Correct answer
C — 1000 m
Learning tip
One repeater links two segments and adds one segment. Up to three repeaters allow four segments in total, each limited to 1000 m with suitable power supply. Distinguish TP-64 from TP-256: capacity depends on product compatibility and available current. 1000 m is the cable-length limit per segment, not proof of compliance; also check distances and load.
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Q47
With the maximum of 3 line repeaters, what is the maximum TOTAL cable length of one line?
- A.1000 m
- B.3000 m
- C.4000 km
- D.4000 m
KNX Topology· Line segment, line, area & network structure· Medium
▸
Correct answer
D — 4000 m
Learning tip
Correct: four 1000 m segments joined by 3 repeaters give a maximum total of 4000 m.
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Q48
What determines whether one and the same coupler hardware acts as a line repeater, a line coupler or a backbone coupler?
- A.A physically different model for each role
- B.The loaded application program and its individual address
- C.Its physical position in the distribution board
- D.The colour of its bus terminal
KNX Topology· Line segment, line, area & network structure· Medium
▸
Correct answer
B — The loaded application program and its individual address
Learning tip
Correct: the source states the loaded application and the individual address determine the role.
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Q49
How many lines can be connected to a main line via line couplers within one area?
- A.16
- B.255
- C.15
- D.4
KNX Topology· Line segment, line, area & network structure· Easy
▸
Correct answer
C — 15
Learning tip
Correct: up to 15 lines can be connected to a main line via line couplers to form an area.
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Q50
Including the mounted line-/backbone couplers, how many bus devices can be topologically addressed on a main line?
- A.255
- B.15
- C.16
- D.256
KNX Topology· Line segment, line, area & network structure· Medium
▸
Correct answer
D — 256
Learning tip
Correct: up to 256 bus devices, including the mounted couplers, can be addressed on the main line.
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Q51
What is the maximum number of couplers (line- or backbone couplers) that a main line may carry?
- A.16
- B.256
- C.15
- D.4
KNX Topology· Line segment, line, area & network structure· Medium
▸
Correct answer
A — 16
Learning tip
Correct: the source states a maximum of 16 couplers on the main line.
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Q52
Approximately how many devices can be installed in one complete area?
- A.More than 250,000
- B.More than 4,000
- C.More than 61,000
- D.Exactly 256
KNX Topology· Line segment, line, area & network structure· Medium
▸
Correct answer
B — More than 4,000
Learning tip
Correct: the source states more than 4,000 devices can be installed in one area.
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Q53
How many areas can be connected to the backbone line via backbone couplers?
- A.61
- B.16
- C.15
- D.255
KNX Topology· Line segment, line, area & network structure· Easy
▸
Correct answer
C — 15
Learning tip
Correct: up to 15 areas (BC 1 to BC 15) can be connected to the backbone line.
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