KNX PARTNER
TRAINING COURSE
KNX System arguments
KNX Association
KNX BASIC COURSE
Table of Contents
1
2
3
4
KNX Association: A brief outline ............................................................................ 3
Activities of KNX Association – International standardization ................................ 4
KNX - difference compared to conventional technology ......................................... 5
KNX System specification....................................................................................... 6
4.1
4.2
4.3
4.4
5
6
7
8
KNX Media ...............................................................................................................6
Areas of application for the various media ................................................................ 7
Types of configuration ..............................................................................................7
KNX interworking ..................................................................................................... 8
Success figures ...................................................................................................... 9
The advantages of KNX ......................................................................................... 9
KNX: Application examples .................................................................................. 10
Selling the benefits .............................................................................................. 12
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1 KNX Association: A brief outline
Figure 1: KNX – The history
KNX Association has been set up in 1990 with headquarters in Brussels (Belgium), then still
called “EIB Association”. The goal of the association was to promote intelligent homes and
buildings in general and the EIB system in particular, which was developed jointly by some
renowned manufacturers.
In 1999 this association merged with two other European associations. These are:
 BCI (France) promoting the Batibus system;
 European Home Systems Association (The Netherlands) promoting the EHS system.
As a result of this merger, the name was changed into “KNX Association”.
KNX Association has the following goals:
 definition of a new truly open standard ‘KNX™’ for intelligent homes and buildings;
 establishing the KNX Trademark as a token for quality and multi-vendor interworking;
 establishing KNX as a European and worldwide standard.
As EIB is backward compatible to KNX, most devices can be labelled both with the KNX as
well as the EIB logo.
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2 Activities of KNX Association – International standardization
KNX Association runs the below activities:
 The further technical development and the promotion of the KNX standard together
with the KNX member companies;
 The further development of the common design and commissioning tool software called
ETS™;
 Sales and support of ETS via the myKNX portal (https://my.knx.org);
 Granting the KNX trademark for KNX compatible products (product certification);
 Promotion of KNX training measures through the certification of training centres and by
making available training documentation;
 National and international standardisation activities;
 Encouraging the setup of national groups;
 Promotion of “scientific partnerships” with technical institutes or universities in order to
promote the KNX system amongst students and for research;
 Technical support for manufacturers wanting to develop KNX compatible solutions;
 Definition of testing and quality standards together with the KNX member companies;
 Promotional activities (web site, fairs, brochures…)
KNX Association consisted of 9 members when it was founded: this number has meanwhile
increased to more than 300 (situation January 2015). The current membership list is
available at any time under www.knx.org.
Figure 2: KNX in standardization
At the end of 2003, the KNX Standard was approved by CENELEC (European Committee of
Electrotechnical Standardisation) as the European Standard for Home and Building
Electronic Systems as part of the EN 50090 Series. The KNX Standard was also approved by
CEN (EN 13321-1 for media and protocol and EN 13321-2 for KNXnet/IP). At the end of
2006, KNX was also approved as a world standard (ISO/IEC 14543-3-1 to 7). Moreover, in
May 2013, the KNX technology has been approved as a Chinese standard (GB/T 20965). KNX
is also approved in the USA as ANSI/ASHRAE 135.
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3 KNX - difference compared to conventional technology
Figure 3: KNX – introduction to the technology
In the case of the most widely used medium “Twisted Pair”, a control cable is laid parallel to
the 230 V cable. This results in the following advantages compared to conventional
installation technology:
 the amount of cabling is considerably reduced when bus devices are arranged in a
decentralized way;
 Increase in the number of possible system functions;
 Improvement of the transparency of the installation.
This control cable:
 connects loads (actuators) and switches (sensors)
 supplies power to the bus devices in most cases.
As all KNX bus devices have their own intelligence, a central control unit (e.g. PC) is not
necessary. KNX can therefore be used both in small installations (flats) as well as large
projects (hotels, administration buildings...).
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4 KNX System specification
4.1 KNX Media
Figure 4: KNX System overview
As explained in the previous paragraph, the exchange of KNX data between devices is
typically done via a separate control cable. KNX data can also be sent via the existing 230 V
cable (“Powerline transmission medium”), wireless (“KNX Radio Frequency transmission
medium”) and via Ethernet/WIFI (“KNX IP”). Via appropriate gateways, transmission of KNX
telegrams is also possible on other media, e.g. optical fibre.
When connecting different media, appropriate media couplers have to be used. The used
medium of a device is visible on the product’s label.
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4.2 Areas of application for the various media
Figure 5: Areas of Application for the various media
4.3 Types of configuration
Depending on what is marked on the label of the device, devices can be configured (i.e.
linked and setting of parameters) via:
 Easy installation techniques (E-Mode): configuration is done without the help of a PC but
with a central controller, push buttons…
This type of configuration is intended for the skilled contractor with basic bus
knowledge. Easy compatible products normally have limited functionality and are
intended for medium size installations.
 System installation techniques (S-Mode): design of the installation and configuration is
done via a PC with the installed manufacturer-independent ETS Software, whereby the
manufacturers’ product data are imported in ETS.
This type of configuration is intended for KNX certified building designers and
contractors and for large size installations.
Some devices allow configuration via easy installation techniques as well as S-mode1. For
instance, products with the LTE label are normally configured via the LTE (Logical Tag
Extended) mechanisms: all devices however include a defined S-mode interface, which
allows linking them with S-mode compliant devices.
1 In the case where the product is also labelled with the EIB logo and the KNX logo, this implies that the product
uses the medium TP and can be configured by ETS.
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4.4 KNX interworking
Figure 6: KNX interworking
Devices from different manufacturers and functional areas that are labelled with the KNX
trademark and using the same configuration mechanism can be linked to form a functioning
installation thanks to the KNX standardization of
 Telegrams: devices usually use standard telegrams for transmission, but in exceptional
cases they also use telegrams with extended length for the transmission of bulky data ;
 Useful data in telegrams: for various functions (amongst others switching, dimming,
shutter control, HVAC …), predetermined formats need to be used in KNX certified
devices.
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5 Success figures2






Millions of installed products
thousands of KNX registered and certified products
more than 370 KNX members (manufacturers)
more than 300 recognized training centres
11 international test labs
hundreds of thousands of implemented projects
6 The advantages of KNX







Increased safety
Economic use of energy during the operation of buildings
Simple adaptation of the electrical installation to the changing requirements of the user
Higher degree of convenience
future-proof installations
Wide range of available off-the-shelf components from many manufacturers
Large service network of qualified contractors/designers/integrators
The above arguments may be evaluated differently depending on the type of client or the
user of the installation e.g. functional building compared to residential building, able-bodied
people compared to disabled people, young people compared to elderly people,….
2 For current figures, please consult the KNX web site (www.knx.org)
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7 KNX: Application examples
Figure 7: Possible application fields
Example 1: Implementation of central functions – when you are
leaving the building, all lights, the water supply and specific sockets
(electric oven…) can be switched off, the KNX alarm system can be
activated and the blinds can be controlled dependent on the time of
day, all with a single command.
Example 2: In conference rooms, theatres as well as living rooms, it is
possible to activate different light scenes depending on the activity.
These light scenes can also be modified by the user at any time. For
example in administration buildings, it is possible to achieve an energy
saving of up to 75% for lighting by implementing constant light control
with only one brightness sensor on each building façade.
Example 3: All the states of the equipment in a flat can be indicated in
clear text and controlled via display units (fixed but also mobile devices
such as smartphones or tablet computers). In the same way This can be
implemented in larger installations using PCs and visualisation
software.
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Example 4: By interfacing a KNX installation with the telephone
network, the user can influence or query the building management
functions (e.g. the heating) using a mobile phone. Alarm signals can be
automatically routed to any required telephone number. KNX
installations can also be remotely serviced and configured by the
installer using any available media (e.g. the Internet). The time
required for maintaining the building management system is thus
considerably reduced.
Example 5: A large conference room should be divided into several
independent areas, if the need arises. By inserting partition walls, the
KNX installation automatically detects the required assignment of
switches and lights per room section. It is therefore not necessary to
change the existing cabling.
Example 6: Any number of panic switches (e.g. activation of all the
lights) can be installed.
At night, the lights between the children’s bedroom and the bathroom
can be activated by pressing a button and deactivated after a set
period.
Example 7: KNX enables individual room control of the heating and
cooling system with the creation of heating and cooling profiles per
room. The heat or cold input for a room is automatically adjusted when
a window is opened. In this way, an energy saving of more than 30%
per year can be achieved.
The heat generation can also be controlled dependent on the heat
requirement of the individual rooms (heat is only produced when it is
actually required).
Example 8: KNX enables presence simulation during the absence of the
building owner.
Example 9: The energy consumption of individual electric circuits can
be monitored by energy sensors /energy actuators and can be
switched off for load management when exceeding predefined
threshold values. Combined with a gateway to Smart Metering devices
or renewable energy sources, it is therefore possible to ensure the
optimal use of self-generated energy (e.g. in combination with a future
electric vehicle).
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8 Selling the benefits
Figure 8: Selling the benefits
During a consultation with a future customer, the electrical contractor or designer should
discuss KNX only in terms of its benefits to the customer and focus on the customer’s needs.
Technology and costs should at first not be in the foreground. This discussion should result
in a system quotation rather than a component quotation. The process should continue as
follows:
 Discuss the system quotation with the customer and again stress the benefits for the
customer;
 If the price for the system is not acceptable, functions should be redesigned (e.g.
switching instead of dimming);
 In extreme cases, the price of the installation can be reduced using the following
components:
 push button interfaces together with conventional push buttons
 push button BCUs
 multiple fold switch actuators
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T: +34 965959511
E: info@futurasmus-knxgroup.com
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KNX PARTNER
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KNX TP Topology
KNX Association
KNX BASIC COURSE
Table of Contents
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Topology - Overall view ............................................................................................. 3
Topology - Line and line segment ............................................................................... 4
Topology - Area ......................................................................................................... 5
Topology - Several areas............................................................................................ 6
Individual address ..................................................................................................... 7
Coupler - Gate function.............................................................................................. 8
Coupler - Block diagram............................................................................................. 9
Coupler - Fields of application .................................................................................. 10
Connecting several lines .......................................................................................... 11
Practical example for explanation of functionality ................................................... 12
Internal line telegram .............................................................................................. 13
Line-crossing telegram ............................................................................................ 14
Area-crossing telegram ........................................................................................... 15
Coupling unit: Routing counter ................................................................................ 16
KNX - Internal and external interfaces ..................................................................... 17
Topology - Structure in building ............................................................................... 18
Backbone- /Line coupler classical structure .............................................................. 19
Taking into account higher telegram rates: IP Network ............................................ 20
Line couplers replaced by KNXnet/IP routers ............................................................ 22
Limits to the use of KNXnet/IP routers ..................................................................... 23
Informative annex - old line coupler type ................................................................. 24
In this chapter the following abbreviations are used:
BC = Backbone coupler
LC = Line coupler
DVC = Bus device
LR = Line repeater
PS/Ch = Power supply with choke
S = Brightness sensor
RC = Routing counter
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1 Topology - Overall view
Backbone line
BC
x.0.0
DVC 1
BC
15.0.0
DVC 49
Main line
LC
x.x.0
LC
DVC 1
x.x.1
Maximum
64 devices
DVC 1
Secondary line (1st line segment)
DVC 63
x.x.63
LR
x.x.128
LR
x.x.64
3x
maximum
64 devices
LR
x.x.192
DVC 63
DVC 65
x.x.65
DVC 129
x.x.129
DVC 193
x.x.193
DVC 127
x.x.127
DVC 191
x.x.191
DVC 255
x.x.255
Figure 1: Maximum topological size of a KNX TP installation
In the figure above the maximum topological size of a KNX TP installation is shown.
The overall view in the above figure shows the possibility to extend a KNX TP installation by
means of line extensions, resulting in different line segments.
A line can be extended once and this extension can be connected two times in parallel,
thereby using line repeaters.
This results into a maximum of 4 line segments.
A line extension is only possible in secondary lines!
In the below illustrations, the details of a KNX TP installation are described one by one.
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2 Topology - Line and line segment
DVC
DVC 64
DVC 1
DVC
1st line segment
DVC
PS/Ch
DVC
DVC
DVC
DVC
Figure 2: Topology - line and line segment
By means of telegrams, each bus device (DVC) can exchange information with any other
device.
Maximum 64 bus devices can be connected to a line segment.
Each line segment requires its own appropriate power supply1.
The actual number of devices per line segment depends on the power supply selected and
the power required by the individual devices.
The bus cable can be branched at any place. The following structure are allowed: star, line
and tree structures (also in combination). A ring structure is however not allowed.
It is possible to save wiring material by using the tree structure.
1 This chapter assumes the use of central power supply units only. For distributed power supply units, consult
chapter “Installation”.
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3 Topology - Area
Main line = line 0
PS/Ch
LC 1
LC 15
PS/Ch
PS/Ch
DVC 1
DVC 1
DVC 63
DVC 63
Line 1
1st line segment
Line 15
1st line segment
Figure 3: Topology - area
If more than 64 bus devices are to be connected in an installation, then in the default
topology (without line extensions) up to 15 lines can be connected to a main line via line
couplers (LC). This line structure is called an area.
It is also possible to topologically address 64 bus devices on the main line. The line couplers
used, topologically belong to the secondary line. The maximum number of bus devices on
the main line decreases - due to the energy consumption - by the number of line couplers
(see Coupler - Block diagram).
On each secondary line (in the default topology, the first line segment) but also on each
main line a power supply unit is required.
Line repeaters may not be used on the backbone or in main lines.
In the default topology (without line repeaters) up to 1,000 devices can be installed in an
area.
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4 Topology - Several areas
Area 15
BC 15
Hauptlinie
SV/Dr
BC 2
Hauptlinie
LK 1
SV/Dr
SV/Dr
Area 1
LK 15
BC 1
PS/Ch
PS/Ch
Area 2
Main line
LK 1
SV/Dr
LK 15
DVC 1
TLN 1
SV/Dr
SV/Dr
LC 15
LC 1
DVC 1
TLN 1
PS/Ch
PS/Ch
TLN 63
DVC 1
TLN 63
Linie 1
1. Liniensegment
DVC 63
DVC 1
DVC 63
Linie 1
1. Liniensegment
DVC 63
DVC 63
Line 1
1st line segment
Line 15
1st line segment
Line 15
1st line segment
Line 15
1st line segment
Figure 4: several areas
If more than 1,000 bus devices are to be connected in an installation or in order to have a
clear line structure in larger installations, the TP installation can be extended by mounting
backbone couplers (BC) via the backbone line.
It is also possible to address 64 bus devices topologically on the backbone line (own power
supply required). The backbone couplers used, topologically belong to the respective
secondary main lines.
The maximum number of bus devices in the backbone line decreases – due to the energy
consumption - by the number of backbone couplers used (see Coupler - Block diagram).
Within a maximum of 15 possible areas, in the default topology approximately 15,000 bus
devices can be connected to the bus system and in the extended topology (with line
repeaters) approximately 58,000.
By dividing the KNX TP installation into lines and areas, the functional reliability is increased
considerably.
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5 Individual address
PS/Ch
Backbone line
BC 1
1.0.0
DVC
0.0.>0
BC 15
15.0.0
DVC
1.0.>0
PS/Ch
Main line
LC 1
1.1.0
LC 15
1.15.0
PS/Ch
PS/Ch
AREA
LINE
A A A A
L L L L
0...15
DVC 63
1.1.63
DVC 1
1.15.1
Line 15
1st line segment
Line 1
1st line segment
DVC 1
1.1.1
DVC 63
1.15.63
BUS DEVICE
B B B B B B B B
0...15
0...255
Figure 5: Individual address
The individual address serves to clearly identify the bus device and describes its location
within the topology.
A =
A =
1…15
0
addresses the areas 1…15
addresses the bus devices on the backbone line
L =
L =
1…15
0
addresses the lines 1…15 in the areas defined by A
addresses the main line of the respective area
B =
B =
1…255
0
addresses the bus devices on the line defined by L
addresses the coupler in the respective line
The individual address of an unloaded bus device is 15.15.255.
New bus devices are also delivered ex-factory with the individual address 15.15.255.
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6 Coupler - Gate function
Primary line
Line coupler or backbone coupler
Filter table
Secondary line
Figure 6: Coupler: gate function
When setting the parameters, a filter table can be loaded into a (line -/ or backbone
coupler). The filter table is created automatically in ETS during the planning & design stage
and contains the active line-crossing group addresses.
All received group telegrams are routed by the couplers if they are listed in the filter table.
In this way, each line works independently. Only line-crossing telegrams are routed.
The yellow LEDs on the coupler flicker when a telegram is received on the respective line.
The line repeater passes on all telegrams; it has no filter table.
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7 Coupler - Block diagram
New line coupler
Primary line on bus connector
Transformer
Flash-ROM with
filter table and
operating system
RAM with
operating data
Electrical
insulation 1000 V
LC/BC
2
Transformer
Secondary line
1
Primary line
Secondary line on bus connector
Figure 7: Block Diagram: new line coupler type
The coupler is designed for DIN rail mounting. In operation, for current line couplers the
primary line as well as the secondary line is connected via standardised bus connectors.
Current couplers (as from July 2003 onwards) can be programmed both from the primary
line as well as the secondary line.
Current couplers are supplied from the primary line and only have one controller. This has
the advantage that the coupler can report secondary line power down.
Current couplers are equipped with Flash ROM memory. Contrary to the old coupler types,
they do not need backup battery power for supplying the memory containing the filter table.
The couplers electrically isolate the lines from each other.
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8 Coupler - Fields of application
Figure 8: Coupler: fields of application
Backbone couplers, line couplers and line repeaters are identical devices. Their tasks depend
on the location and the corresponding assigned individual address.
The coupler can be used as:
Backbone coupler BC

Connection between: backbone line – main line
Line coupler LC

Connection between: main line – secondary line
Line repeater LR

For extending a line by a line segment with up to 64 additional
bus devices and an additional cable length of 1,000 m.
Backbone couplers and line couplers only forward line-crossing telegrams.
The line repeater does not have a filter table and therefore forwards all telegrams.
It is the assigned individual address that designates a coupler either as a backbone coupler, a
line coupler or a line repeater. The address 1.1.0, for example, defines the device as the line
coupler of line 1 in area 1.
The line coupler monitors the data communication between the main line and the secondary
line and vice versa. Only the telegrams of which the group addresses are stored in its filter
table are routed.
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9 Connecting several lines
PS/Ch
Switch
Actuator
Line 0
SV/Dr
PS/Ch
Switch
Actuator
LC
2
1
Line 1
SV/Dr
PS/Ch
Switch
Actuator
LC
2
1
Line 2
Figure 9: connecting several lines
In an installation consisting of several lines, each line or each line segment must have its own
power supply unit and choke.
The above figure shows a power supply unit with an integrated choke as well as the line
coupler.
Both lines, the secondary line (e.g. line 1) as well as the primary line (line 0) are connected to
line coupler (current version) via standard bus connectors.
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10 Practical example for explanation of functionality
Figure 10: Practical example
The push button P1 shall switch the lights L11, L12 and L13.During configuration, group
address 5/2/66 is attributed to the push button. The same address is also attributed to the
actuators controlling the before-said lamps.
The push button P2 shall switch the lights L21, L22 and L23. During configuration the group
address 5/2/67 is assigned to it. Again the same address is attributed to the actuators
controlling these lamps.
The brightness sensor S1 shall also switch the lights next to the window (L11 and L21). Group
address 0/2/11 is therefore attributed to the sensor as well as to the actuators controlling
the window lights (L11 and L21).
The window lights can therefore be switched via the push button as well as the brightness
sensor.
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11 Internal line telegram
KNX
P1
5/2/66
L11
5/2/66
0/2/11
L21
5/2/67
0/2/11
P2
5/2/67
L12
5/2/66
L22
5/2/67
S1
0/2/11
L13
5/2/66
L23
5/2/67
Figure 11: Internal line telegram
Pressing push button P1 sends a telegram with the group address 5/2/66.
Although all bus devices listen in when the telegram is transmitted, only the actuators of
lamps L11, L12 and L13 with the same group address 5/2/66 execute the command.
If the brightness sensor sends the group address 0/2/11, all the bus devices on this line listen
in but only the actuators of the window lights L11 and L21 execute the command.
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12 Line-crossing telegram
Main line
LC 1
LC 2
P1
5/2/66
L13
5/2/66
S1
P2
5/2/67
L21
5/2/67
0/2/11
L11
5/2/66
0/2/11
L22
5/2/67
L12
5/2/66
L23
5/2/67
0/2/11
Figure 12: Line-crossing telegram
If the brightness sensor is not connected in the same line as the lamp it has to control, it is
necessary to transmit its telegrams via the main line.
By its parameterization, the line coupler LC2 is aware of the fact that there are bus devices
outside its own “line 2” responding to telegrams transmitted by the brightness sensor. LC 2
therefore routes the group telegram 0/2/11 onto the main line.
Line coupler LC1 is aware of bus devices on its “line 1” that respond to the group telegram
0/2/11 and therefore transmits the telegram into its line.
All the bus devices on this line listen to the telegram from the brightness sensor but only the
actuators controlling the lights L11 and L12 execute the command.
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13 Area-crossing telegram
Backbone line
BC 1
BC 2
Main line
LC 1
LC 2
5/2/66
L11
5/2/67
L21
0/2/11
0/2/11
P1
L12
5/2/66
L22
5/2/67
L13
5/2/66
L23
5/2/67
5/2/66
S1
0/2/11
Figure 13: Area-crossing telegram
If brightness sensor S1 is mounted in another area, it can still address all bus devices via the
backbone line.
If the group address 0/2/11 is assigned to the brightness sensor, the telegram is routed to
line 1 via the backbone couplers BC 1 and BC 2 and line coupler LC 1.
The actuators controlling lights L11 and L21 in area 1, line 1 then execute the command.
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14 Coupling unit: Routing counter
RC = 3
BC
BC
RC = 4
RC = 2
LC
LC
RC = 5
RC = 1
LR
LR
RC = 6
RC = 0
DVC
DVC
Figure 14: Routing counter
The telegram transmitted by the sending device contains a routing counter, of which the
initial count value is 6.
Each coupler decrements the routing counter and passes on the telegram as long as the
value has not reached 0.The filter table entries are taken into account.
If a service device, however, transmits a telegram containing a routing counter value of 7,
the coupling units do not alter this value. In this case the filter table is ignored and all line
couplers in the installation route the telegram. It finally reaches the bus devices it is
intended for, no matter which line they are connected to.
In case of (unintentional) loops in the installation, the routing counter limits the number of
circling telegrams.
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15 KNX - Internal and external interfaces
PS/Ch
Backbone line
BC 1
PS/Ch
Gateway
Other
systems
Main line = Line 0
LC 1
LC 15
PS/Ch
DVC 1
Line 15
1st line segment
Line 1
1st line segment
PS/Ch
DVC 63
DVC 1
DVC 63
Figure 15: KNX - internal and external interfaces
KNX is open to be linked to any other system. The backbone line (or any other line) can be
connected via a gateway unit to e.g. PLC, ISDN, building management technology, Internet
etc.
The gateway unit converts the protocol bi-directionally.
Media couplers connect different types of KNX media (e.g. Twisted Pair and Powerline 110).
Parts of KNX installations can also be linked via optical fibre. The benefits of this are
electrical separation and greater cable lengths.
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16 Topology - Structure in building
Figure 16: Division of lines in a medium sized project (example)
After the above theoretical introduction, some practical information (the above picture is by
the way explained in detail in chapter “ETS Project Design – Advanced”).
Ideally, a building does not contain more than 50 installed bus devices per floor. Or one can
– as shown in the above picture, make a division according to the different wings of the
building. It is clear that in this case the better overview will be realised when line numbers
correspond to floor numbers and area numbers correspond to building - or wing numbers.
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17 Backbone- /Line coupler classical structure
Backbone-/ Line coupler classic
Line 1.4
Line 1.2
Line 1.1
Floor 4
LC
1.4.0
LC
1.3.0
LC
1.2.0
LC
1.1.0
Area 1
(West wing)
Floor 3
Floor 2
Backbone line 0.0
LC
2.4.0
Line 2.4
LC
2.3.0
Line 2.3
Line 2.2
LC
2.2.0
Line 2.1
LC
2.1.0
Floor 1
BC
1.0.0
Line 2.5
LC
2.5.0
Floor 5
Main line 2.0
Line 1.3
LC
1.5.0
Main line 1.0
Line 1.5
BC
2.0.0
Area 2
(East wing)
Figure 17: Backbone- /Line coupler classical structure
Of course it will not be possible to realize this under all circumstances. As line repeaters can
be installed (as already indicated before), such a floor may be equipped with up to 253
devices, without having to violate the above structure (taking into account that line
repeaters have to be counted double as discussed before, the normal maximum number of
devices of 256 is reduced by 3). With that many devices it is possible to realize nearly any
application, thanks to the current evolution in the development of KNX devices and the
availability of input - / output devices with in the mean while more than 16 channels.
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18 Taking into account higher telegram rates: IP Network
LAN
Router
Network - Switch
KNXnet/
IP-Router
1.2.0
DVC
1.1.1
DVC
1.1.2
PS/Ch
KNX
KNX
PS/Ch
KNXnet/
IP-Router
1.3.0
DVC
1.2.1
PS/Ch
KNX
KNXnet/
IP-Router
1.1.0
DVC
1.2.2
DVC
1.3.1
DVC
1.3.2
Figure 18: Replacing line couplers by so-called KNXnet/IP routers
As explained in the previous paragraph, gateways to other systems can be installed on all
levels. Increasingly, this is requested in bigger projects as a result of higher customer
demands.
An important reason is the increased telegram load, which can occur when the user makes
use of visualisation software and devices with a higher number of channels, all of which
automatically returning multiple status acknowledgements.. In the latter case, a pure TP
topology is overloaded as transmission speed on main – and backbone lines is limited to 9,6
Kbit / sec. In such a case one can easily use an IP network as a substitute for main – or
backbone lines, by using the coupler type that was designed for this purpose.
As you can see from the above picture, the main line has been replaced by an IP network.
This has the advantage that all vertical operations e.g. the (bi-directional) communication
between a building central and KNX is only determined by the bit rate of the secondary line
(Ethernet is at least 1000 times faster; with the so-called “Gigabit” – switches it is possible to
transmit data on the Ethernet 100 000 times faster). The parallel connection of several lines
is no longer an issue. The standardized type of communication applied here is called
“Tunnelling”. It is in other words the well-known gateway function, which is also used by ETS
for remote programming across IP. A building central can be connected simultaneously to
several gateways, multiplying the total data rate.
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A different story is the direct communication between the individual KNX lines. The
KNXnet/IP router makes use of another procedure which is called “routing”, or the actual
line coupler function. Principally it works in the same way as routing across a TP main line: A
KNXnet/IP router wanting to send a line-crossing telegram, will send this with a so-called
“Multicast” IP address into Ethernet. All other KNXnet/IP routers are assigned to this
multicast address, and are able to receive and evaluate this telegram. The normal line
coupler function is now again applied, i.e. the comparison with the also here required filter
table (group telegrams) or the line address (individual addressed telegrams) resulting in the
blocking or routing of telegrams, depending on the case.
Please note the following with regard to multicast addresses:
a) There is a dedicated worldwide registered KNX multicast address, which is preprogrammed in the software of the KNXnet/IP router. This multicast address can be
changed within the limits of the available address range for IP communication.
b) The network switch and area router in the LAN network must be fit to handle
multicast telegrams. In case of doubt you should discuss this matter in advance with
your network administrator.
c) The multicast addresses cannot be used across Internet, except across a VPN
connection.
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19 Line couplers replaced by KNXnet/IP routers
Line coupler replaced by KNXnet/IP Router
Line 1.5
Line 1.4
KNXnet/
IP-Router
1.5.0
Floor 5
KNXnet/
IP-Router
Floor 4
1.4.0
Line 1.3
KNXnet/
IP-Router
KNXnet/
IP-Router
Floor 3
KNXnet/
IP-Router
1.1.0
Area 1
(West wing)
2.5.0
KNXnet/
IP-Router
Line 2.4
KNXnet/
IP-Router
Line 2.3
2.3.0
Floor 2
1.2.0
Line 1.1
Line 2.5
2.4.0
1.3.0
Line 1.2
KNXnet/
IP-Router
KNXnet/
IP-Router
Line 2.2
2.2.0
Floor 1
Network
(LAN)
KNXnet/
IP-Router
Line 2.1
2.1.0
Area 2
(East wing)
Figure 19: Our picture again: line couplers have now been replaced by KNXnet/IP routers. This picture
represents the underneath explained case 1.
Just like the TP/TP coupler, the KNXnet/IP router can be used as a line coupler as well as a
backbone coupler. If the KNXnet/IP router replaces the line coupler, all main lines and
basically also the backbone line are replaced by Ethernet (Case 1).
If backbone couplers are replaced by KNXnet/IP routers, the normal line couplers can
remain, as only the backbone line is replaced by the LAN (Case 2).
Which case is more appropriate depends more or less on the - to be expected telegram rate
requirements on main – and backbone lines. Theoretically, a third case is possible, as a
combination of case 1 and 2, with normal TP areas with a KNXnet/IP router on top and also
with lines with IP routers instead of line couplers. This option should however be chosen in
exceptional cases. The topic is described in more detail in the KNX advanced course.
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20 Limits to the use of KNXnet/IP routers
Even if the high bit rate of Ethernet considerably facilitates heavy telegram traffic and
minimizes telegram loss, one should warn not to thoughtlessly program bus devices sending
out telegrams too frequently. The fast Ethernet will not help if for instance telegrams are
sent out simultaneously from all lines into one single line. To explain it with a metaphor: the
case would be similar to all cars accessing a 1,000 lane motorway via 100 entries but all of
them also wanting to exit via a single lane exit. This is by the way not a KNX related problem:
it is common to all mesh structured data networks.
Only a meaningful organisation of communication between bus devices and lines will be able
to prevent a very unlikely but still possible loss of data.
This however should be easily possible if one has sufficient knowledge on bus devices and
their respective parameters.
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21 Informative annex - old line coupler type
Old line coupler type
Secondary line on data rail
Secondary line
Spring contacts
Electrical insulation 600 V
Bus coupling
Logic
Filter table
230 V
50/60 Hz
> 100 ms buffer
SV +
Bus +
Bus SV -
Lithium battery
> 10 years
Bus coupling
Power supply unit
Choke
Connector
LC
640 mA
Main line
Primary line on bus connector
Figure 20: Block Diagram: old line coupler type
In earlier installations (until June 2003) line couplers were installed where power supply for
both bus coupling units, logic and the filter table memory were supplied from the secondary
line.
The primary line of this type of coupler, which is 4 respectively 1 unit wide, is connected via
standardized bus connectors and the secondary line by means of a data rail (spring
contacts). The connection to the bus cable is established by means of a data rail connector
(2-pole or 4-pole).
A lithium battery (with a life span of more than 10 years) provides the backup supply for the
memory containing the filter table, also in the case of a bus power down. New line couplers
are equipped with a flash ROM memory and therefore do not need backup battery power.
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Futurasmus Zentrum
KNX++ TRAINING CENTER
C/ de la Nit. 1, Bloque 7, Local 1 03110
Mutxamel (Alicante)
T: +34 965959511
E: info@futurasmus-knxgroup.com
www.futurasmus-knxgroup.org
A.
0
L.
0
CB.
0
15
15
255
.
.
.
.
TCP/IP
KNXnet/IP
0.0.0
> 58000
0.0.4
FA
1
1.0.0
15
4.0.0
FA
1.0.4
FA
FA
1
15
1.1.0
FA
FA
FA

FA
FA
15.3.0
8
15
FA
FA
ETS
1.1.128
FA

1.1.3

PC

64
USB
FA
FA
3
1.1.1
64
FA
1
15.3.100
15.8.4
A.
0
L.
0
CB.
0
15
15
255
.
.
.
.
TCP/IP
KNXnet/IP
0.0.0
> 58000
0.0.4
FA
1
1.0.0
15
4.0.0
FA
1.0.4
FA
FA
1
15
1.1.0
FA
FA
FA

FA
FA
15.3.0
8
15
FA
FA
ETS
1.1.128
FA

1.1.3

PC

64
USB
FA
FA
3
1.1.1
64
FA
1
15.3.100
15.8.4
FA
USB
PC
ETS
L
MT1
1.1.10
1.1.1
ALT
1/1/1
ALT
1/1/2
ALT
1/1/5
ALT
1/1/3
N
1/1/8
1/1/8
1/1/1
1/1/7
1/1/8
1
2
3
1.1.2
ON
1/1/6
OFF
1/1/6
1.1.3
1/1/8
1/1/7
1/1/5
1/1/8
1/1/7
1/1/6
4
1.1.8
ALT
1/1/7
OFF
1/1/8
N
MT2
1/1/2
1/1/3
L
5
KNX PARTNER
TRAINING COURSE
KNX System overview
KNX Association
KNX BASIC COURSE
Table of contents
1
2
3
Definition .................................................................................................................. 3
Minimal structure of a KNX TP installation ................................................................ 4
Addressing ................................................................................................................ 5
3.1
3.2
3.3
3.4
4
5
6
Individual address ........................................................................................................ 6
Group address .............................................................................................................. 7
Configuration steps .................................................................................................... 11
Function after commissioning stage ............................................................................ 12
Group object ........................................................................................................... 13
Useful data of a TP telegram ................................................................................... 14
Standardised datapoint types .................................................................................. 15
6.1
6.2
6.3
6.3.1
6.3.2
6.3.3
6.4
7
8
9
10
11
12
On/Off (1.001) ........................................................................................................... 16
Functional block „Shutter and blinds actuator - basic“................................................. 17
Functional block „Dimming“ ....................................................................................... 18
Switching - On/Off (1.001)............................................................................................................. 18
Relative dimming (3.007) .............................................................................................................. 18
Absolute dimming – Scaling (5.001) .............................................................................................. 19
2-octet float value (9.0xx)........................................................................................... 19
TP bit structure ........................................................................................................ 20
Telegram collision ................................................................................................... 21
Symmetrical signal transmission .............................................................................. 22
Superimposing data and supply voltage .................................................................. 23
Connection of the power supply unit to the TP bus................................................... 24
Cable lengths .......................................................................................................... 25
12.1
12.2
12.3
Cable length between TP power supply unit – TP bus device ....................................... 26
Cable lengths between two TP bus devices ................................................................. 27
Total cable length per TP line segment........................................................................ 27
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1 Definition
The following terms are used as synonyms in KNX literature:
Terms used in the KNX training
documentation and in ETS
Alternative term
Individual address
Physical address
Group object
Communication object
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2 Minimal structure of a KNX TP installation
Figure 1: Minimal structure of a KNX TP installation
A minimum TP KNX installation consists of the following components:
KNX Power supply unit (30 V DC)
Choke

Can also be integrated in the power supply
unit.
Sensor(s)

A single push button with two rockers is
represented in the figure above

Sensors usually get their power from the
KNX power supply unit.
Actuator(s)

A single switch actuator is represented in
the figure above
Bus cable

only two wires of the bus cable are
required

In the figure above it is represented as a
green line

Connects sensors, actuators and KNX
power supply unit.

Serves for data exchange and for providing
ancillary power
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3 Addressing
In KNX there are two types of addressing, i.e. the individual addressing and the group
addressing.
Figure 2: Addressing
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3.1 Individual address1
Figure 3: Structure of the individual address
An individual address shall be unique within a KNX installation. Its primary goal is to forward
“programming telegrams”, new application - / and parameter data via the ETS to the bus
device.
The individual address in a telegram has a fixed structure of 16 bits and has the format as
shown in the figure above.
In the user interface of ETS and in KNX documentation, individual addresses are represented
in decimal format with two separating points.
The bus device is usually prepared for the acceptance of its individual address by pressing a
programming button on the bus device. The programming LED is lit during this process.
The individual address is permanently assigned to the bus device by means of ETS. ETS is
now able to forward all required data (application, configuration, parameters, group
address assignments) via the bus to the device.
If the commissioning including all customization and diagnostic steps have been carried out,
the communication (e.g. light on/off) is exclusively done via group addresses.
1 Synonym for “physical address”
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3.2 Group address
Figure 4: Structure of group addresses
The normal communication between devices in an installation is carried out via group
addresses. The project engineer defines for each function in the installation an appropriate
group address. He can freely select the group address structure.
65535 group addresses are available2. Only the group address 0/0/0 is reserved for so-called
broadcast communication (telegrams to all available bus devices). An example of a
broadcast message is the allocation of an individual address.
2 Only valid from ETS4 onwards. Until ETS3 the most significant bit was set to 0. Main groups were therefore
limited from 0….15. 32767 group addresses were available in total.
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For each ETS project it is possible to select the representation of group addresses in a:
 3-level structure (main group / middle group / subgroup)
 2-level structure (main group / subgroup)
 Freely defined structure
The levels only serve for a clearer overview of the functions / group addresses created in
ETS.
The default level is the 3-level structure. The level structure can be set for each project in
the project properties of ETS.
Example of a 3-level structure:
5/2/66
5/2/67
5/2/68
14/2/69
Etc.
Room 424, switch light 1
Room 424, switch light 2
Room 424, switch all lights together
Switch lighting building 4
The free group address structure offers the most flexible structuring option (see chapter
Project planning – Basic).
The meaning of each individual level can be freely defined by the ETS project engineer.
A common structure is however the following:
Main group
Floor number
Middle group
Functional domain (e.g. 1 = lighting, 2 = heating, 3 = Shading, …)
Subgroup
Function of load or group of loads
(e.g. Light 1 R424 on/off, Window bedroom open/close, Ceiling living
room on/off, Ceiling living room dimming, Blinds room 424
up/down,…)
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Figure 5: Example: structure of group addresses in ETS
It is recommended to define a company default group address structure and to stick to this
structure in all projects in order to facilitate the insight into different projects.
Each group address can be assigned to bus devices at one’s discretion, regardless where the
device is installed.
The group addresses are assigned to the group objects of the respective bus devices, either
with the help of ETS (S-mode) or automatically and invisible in E-mode.
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Summary:
The individual address is important for the commissioning and diagnostic in an installation
via ETS (in order to address individual devices).
Group addressing dominates however during “normal operation” of a KNX installation : in
that case, the individual address is of a lesser importance.
Address type
Application
See example letter post
Individual address
Target address in ETS „programming
telegrams“ in order to forward to one
single bus device new application – /
and parameter data.
To
John Smith
Samplestreet 12
US-12345 Tinseltown
Group address
Target address in „normal“ operation
telegrams like e.g. “Lighting room 424
on/off”
Bulk mail
To all households with a
photovoltaic installation
Important note3:
Actuators can listen / react to several group addresses.
Sensors can however send only one group address per telegram
Note:
 When using main groups 14 to 31 in ETS, one should take into account that these group
addresses could until now not be filtered individually by TP line -/ backbone couplers.
This could negatively influence the dynamics of the entire bus system. Consequently,
these main groups are to be used primarily for central functions.
 The number of group addresses that can be assigned to sensors and actuators is variable
and is limited by the memory size of the bus device. ETS will prevent that the available
memory space is exceeded and will give an appropriate warning to the ETS user.
3 These rules of thumb have been somewhat simplified. More precisely, one should state: group objects can
react to several group addresses, however - after an event (e.g. pressing a rocker) - only the first group address
assigned to a sensor object will be used during sending.
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3.3 Configuration steps
After mounting the devices, a KNX installation (especially for S-mode compatible products)
is not ready for operation until sensors and actuators have been loaded with the application
software via the ETS program. The project engineer first needs to carry out the following
configuration steps using ETS:
 assigning individual addresses to the different devices (for the unique identification of a
sensor or actuator in a KNX installation);
 selecting the appropriate application software for the bus devices;
 Setting the parameters for the bus devices;
 Assigning group addresses in order to logically connect sensors and actuators and by
doing so realize the desired functions.
In the case of E-mode compatible products, the same steps as above are applied, whereby
the settings for:
 the individual addresses, but also
 the parameters of the bus devices and
 the group addresses (for linking the functions of sensors and actuators)
is done either via local settings on the products or automatically or semi-automatically by a
central controller module.
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3.4 Function after commissioning stage
Figure 6: Function after commissioning stage
After configuration, the installation functions as follows:
 If the upper rocker of the single push button (1.1.1) is pressed, it sends a telegram
containing the group address (5/2/66) and the value (“1” = switch on)
 This telegram is received and evaluated by all connected bus devices.
 All devices that have the same group address will:
 synchronously send an acknowledgement telegram (reception correct / reception
incorrect);
 read the value and behave accordingly.
In our example, the switch actuator (1.1.2) will close its output relay because group
address 5/2/66 was also assigned to it.
When the lower rocker is pressed, the same happens except that this time the value is set to
“0” and the output relay of the actuator is opened.
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4 Group object
Push button 2-fold
No. 0 5/2/66
Switch Actuator 2-fold
Left rocker
No. 0 5/2/66
Channel A
No. 1 5/2/67 Right rocker
No. 1 5/2/67
Channel B
Individual address
1.1.1
Individual address
1.1.2
2
2
230 V
KNX
Figure 7: More detailed description of bus devices with group objects
In the previous introduction example, a group address was assigned directly to a bus device
(single Push button – single channel Actuator).
In reality, one needs to think one level deeper, as there can be several channels that can
communicate in a device. Obviously this is the case when a push button has more than one
rocker or when an actuator has more than one switching output.
The individual rockers of a push button or the several switching outputs of an actuator are
represented by so-called “group objects”.
KNX group objects represent memory locations in a bus device. The size of these objects can
vary between 1 bit and 14 bytes. The size of the group objects is defined by the
manufacturer and depends on the related function.
As only two states (0 and 1) are required for switching, 1 bit group objects are used in this
example. The data for text transmission is more bulky and therefore group objects with a
maximum size of 14 bytes are used.
ETS only allows linking by means of group addresses group objects with the same size.
Several group addresses can be assigned to one group object, but only one (the first one) is
the sending group address.
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Figure 7 shows the relation using a push button 2-fold and a switch actuator 2-fold as an
example.
A group communication in detail:
a) If e.g. the upper left rocker of a 2-fold push button is pressed, it will write a “1” to its
group object with the number 0. Consequently, the firmware in the device ensures that
a telegram is sent on the bus with the information “Group address 5/2/66, write value,
Value = “1”.
b) All bus devices mounted in the KNX installation, to which the group address 5/2/66 have
been assigned (and thus listen to 5/2/66) will then take over the “1” in their own group
object. In our example, the actuator will take over the value “1” in its group object with
number 0.
c) The application software of the actuator establishes that the value in this group object
has changed and executes the switching process.
5 Useful data of a TP telegram
Figure 8: Useful data of a TP telegram
The length of the data depends on the data point type used and can vary between 1 bit and
14 bytes.
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6 Standardised datapoint types
Figure 9: Standardised datapoint types (selection)
Several datapoint types were standardised to guarantee compatibility of similar devices
from different manufacturers (e.g. dimmer, clock).
Both the data format as well as structure of the group objects both for sensor and actuator
functions is part of the data point standardization.
The combination of several standardised datapoint types is called a functional block.
The name of a group object can be freely decided by the manufacturer. For instance, a
DPT_Step is sometimes, depending on the manufacturer, referred to as short operation or
as blind operation. This does however not imply that the use of the DPT is limited to this
area of application. For example “Scaling” (Type 5.001) can be used both for setting a
dimming brightness or for setting a heating valve position.
In the following pages examples of a number of data point types are presented. The full list
of all approved datapoint types can be downloaded from the KNX Association’s web site
(www.knx.org).
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6.1 On/Off (1.001)
Figure 10: DPT On/Off (1.001),...
DPT_Switch (on/off) is used for switching an actuator function. Other one bit datapoint
types are defined for logical operations (Boolean 1.002), for Enable/Disable (1.003), etc....
Other functions or extensions to the pure switching function (inversion, time delay and
toggle switch functions etc.) are not part of the datapoint type, but are parameters of the
functional block specification, in which this DPT is used (e.g. functional block light switch).
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6.2 Functional block „Shutter and blinds actuator - basic“
Figure 11: Functional block “shutter and blinds actuator – basic”
The functional block “Shutter and blinds actuator –basic ” is especially used for controlling
shutter and blind drive mechanisms and consists of two group objects with the underneath
mentioned datapoint types:
 Up/Down (DPT 1.008)
 Step/Stop (DPT 1.007).
By writing on the object with ”Up/Down”, a drive is set in motion from an idle state or
changes direction while moving.
By writing on the object “Step”, a drive which is already in motion is brought to a stop or a
halted drive is set in motion (slats adjustment) for short periods (step-by-step).
Important: Group objects using this function should never reply to read requests via the bus
as they may unintentionally stop moving drives or set halted drives in motion. The “read”
flag should therefore be deleted in the relevant group objects – both in sensors as well as
actuators. This especially applies for central functions.
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6.3 Functional block „Dimming“
Figure 12: Functional block Dimming
Apart from the 4 bit object (Relative dimming - DPT_Control_Dimming [3.007]), the
functional block dimming consists of at least a switching object (corresponds to DPT_Switch
[1.001]) and a value object (corresponds to DPT_Scaling – [5.001]).
6.3.1 Switching - On/Off (1.001)
Explained in § 6.1.
6.3.2 Relative dimming (3.007)
A dimming command, relative to the current brightness setting, is transmitted to the
dimming actuator using the relative dimming object DPT_Control_Dimming.
Bit 3 of the useful data determines whether the addressed device dims down or up
compared to the current brightness value.
Bits 0 to 2 determine the dimming step. The smallest possible dimming step is 1/64th of 100
% (1 % in the ETS group monitor).
Figure 13: Dimming steps in ETS
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6.3.3 Absolute dimming – Scaling (5.001)
Figure 14: Scaling – Absolute dimming
With “Absolute dimming” (DPT_Scaling), a brightness value between 0,4 % (minimum) and
100 % (maximum) is set directly.
Depending on the manufacturer‘s application, it may be possible to switch on
(0,4 % <= value <= 100 %) or off (value = 0) a connected device using this DPT.
This group object has a size of 1 byte.
6.4 2-octet float value (9.0xx)
Figure 15: 2-octet float value (9.0xx)
With this data format positive or negative float values with a maximum resolution of 0,01
can be transmitted. This data format is used in many datapoint type definitions e.g. for
transmitting room temperatures in DPT „Temperature (°C)“ or „Speed (m/s)“.
Group objects with this data format have a size of 2 bytes.
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7
TP bit structure
Figure 16: TP bit structure
A “bit” can have two logical states, i.e. “0” and “1”.
Technical logic in KNX TP:


During logical state “1” no signal voltage
During logical state “0”  signal voltage
This means that if several bus devices transmit simultaneously, the logical state “0” will
prevail!
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8 Telegram collision
Figure 17: Telegram collision
A bus device with data to transmit may start transmission immediately if it detects that the
bus is unoccupied.
The simultaneous sending request of several bus devices is controlled by the CSMA/CA
procedure (Carrier Sense Multiple Access with Collision Avoidance).
The bus devices listen to the bus while transmitting. As soon as a bus device with the logical
state “1” detects the logical state “0” (= flow of current on the line), it stops transmitting to
give way to the other sending device.
The bus device that terminated its transmission continues to listen to the network to wait
for the end of the telegram transmission and then retries its transmission.
In this way, if several bus devices attempt to transmit simultaneously, the CSMA/CA
procedure ensures that only one of these bus devices can terminate its transmission
without interruption. The data throughput is therefore not reduced.
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9 Symmetrical signal transmission
Figure 18: Symmetrical signal transmission
The data is transmitted symmetrically over the pair of wires. Not any of the wires is
connected to the ground or PE or has a fixed potential.
The bus device only evaluates the difference of the AC voltage between both wires.
As radiated noise affects both wires with the same polarity, it has no influence on the
difference in the signal voltage.
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10 Superimposing data and supply voltage
Figure 19: The transformer-IC in the bus device separates DC supply voltage and AC Information voltage
Data is transmitted in the form of AC voltage. It is superimposed onto the DC supply voltage.
Both voltage parts are separated by the transformer-IC.
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11 Connection of the power supply unit to the TP bus
Figure 20: Connection of power supply to TP bus
The power supply feeds the bus via the choke. A voltage regulator is included in the power
supply, which tries to immediately correct deviations in the 30 V nominal voltage. If the
installation were connected directly to the power supply, the voltage regulator would try to
also correct the AC information voltage. This would result in a “tug of war” between the
sending bus device and the regulator included in the power supply.
The choke with its inductance brings some “inertia” into the system.
It allows short-time deviations to the 30 V voltage and at the same time allows the
regulation of the DC supply voltage.
The second task of the choke is the generation of the second (positive) half of the AC
voltage pulse. Only the first (negative) half is generated by the sending bus device. The
cooperation between bus device and choke results in an AC signal voltage without a DC
part. This is important for the correct signal evaluation in receivers.
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12 Cable lengths
Figure 21: cable lengths
Power Supply Unit - Bus device ....................................................................... max. 350 m
Bus device - Bus device .................................................................................... max. 700 m
Total bus line length ....................................................................................... max. 1000 m
Distance between 2 power supply units in one line………See manufacturer instruction
If using decentralised power supply, check the chapter ‘installation’.
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12.1 Cable length between TP power supply unit – TP bus device
Figure 22: Cable length between TP power supply unit – TP bus device
A bus device only transmits a half wave (shown in the picture as the negative half wave at
the positive wire).
The choke as part of the power supply unit produces - together with the transformers of the
bus devices - the positive equalisation pulse.
As the choke plays a significant role in the forming of the equalisation pulse, the bus devices
may only be installed up to 350 m cable length away from the choke (power supply unit).
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12.2 Cable lengths between two TP bus devices
Figure 23: Cable lengths between two TP bus devices
A telegram transmission over the cable requires a certain transit time.
If several bus devices try to transmit simultaneously, a possible collision can only be
resolved up to a distance of 700 m (delay time of the signal tv = 10 µs).
12.3 Total cable length per TP line segment
The signal of the sending bus device will be damped by the continuous loading and
unloading of the cable capacity. At the same time, the signal edges are rounded by the cable
capacity. The signal level drops due to the resistive load (bus cable and device).
To ensure that data is reliably transmitted despite these two effects, the total cable length
per line segment may not exceed 1,000 m. The maximum number of devices per line
segment depends on their total power consumption.
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Futurasmus Zentrum
KNX++ TRAINING CENTER
C/ de la Nit. 1, Bloque 7, Local 1 03110
Mutxamel (Alicante)
T: +34 965959511
E: info@futurasmus-knxgroup.com
www.futurasmus-knxgroup.org
N
F
220V AC
29V AC
KNX
29V DC
P=
29V DC
0
104 μS
1
1
0
1
VI
1
Powered by TCPDF (www.tcpdf.org)
1.1.2
ON
INSTALACIÓN ALICANTE
100%
1/1/1
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1/1/1
1 bit
1 bit
INSTALACIÓN MADRID
1/1/1
1/1/1
4 bit
0 0 0 1
CAMPO DE CONTROL
1 0 1 1 1 1 0 0
K
N
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R K P
E N R
P X I
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P
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A
M
B
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L
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DIRECCIÓN DE ORIGEN
DIRECCIÓN DE DESTINO
0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0
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1
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PRIO = 0 0 = SISTEMA
1 0 = ALARMA
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1/1/1
T
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L + 1 = LONG D.U.
Ej. L = 1 = LONG D.U. - 1
LONG D.U. = L + 1 = 1 + 1 = 2
COMANDO
0000 = LEER VALOR
0001 = RESP. VALOR
0010 = ESCR. VALOR
1010 = ESCR. MEM.
(B.S.)
4
1.1.2
ON
INSTALACIÓN ALICANTE
100%
1/1/1
-
1/1/1
1 bit
1 bit
INSTALACIÓN MADRID
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1/1/1
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0 0 0 1
CAMPO DE CONTROL
1 0 1 1 1 1 0 0
K
N
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R K P
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P X I
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P
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A
M
B
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L
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DIRECCIÓN DE ORIGEN
DIRECCIÓN DE DESTINO
0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0
1
A
1
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PRIO = 0 0 = SISTEMA
1 0 = ALARMA
ETS MOD. 
0 1 = ALTA
1 1 = NORMAL / BAJA
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0 = SI
0 0 0 1
2
C8
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0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 1
1/1/1
T
I
P
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0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1
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D
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T.
TD = 1 = DG
0 = D.F. = D.I.
C
O
M
A
N
D
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L = LONG D.U. - 1
L + 1 = LONG D.U.
Ej. L = 1 = LONG D.U. - 1
LONG D.U. = L + 1 = 1 + 1 = 2
COMANDO
0000 = LEER VALOR
0001 = RESP. VALOR
0010 = ESCR. VALOR
1010 = ESCR. MEM.
(B.S.)
4
1.1.2
ON
INSTALACIÓN ALICANTE
100%
1/1/1
-
1/1/1
1 bit
1 bit
INSTALACIÓN MADRID
1/1/1
1/1/1
4 bit
0 0 0 1
CAMPO DE CONTROL
1 0 1 1 1 1 0 0
K
N
X
R K P
E N R
P X I
O
P
R
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A
M
B
U
L
O
DIRECCIÓN DE ORIGEN
DIRECCIÓN DE DESTINO
0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0
1
A
1
L
PRIO = 0 0 = SISTEMA
1 0 = ALARMA
ETS MOD. 
0 1 = ALTA
1 1 = NORMAL / BAJA
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0 = SI
0 0 0 1
2
C8
D.U.
0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 1
1/1/1
T
I
P
O
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0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1
L
D
E
S
T.
TD = 1 = DG
0 = D.F. = D.I.
C
O
M
A
N
D
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L = LONG D.U. - 1
L + 1 = LONG D.U.
Ej. L = 1 = LONG D.U. - 1
LONG D.U. = L + 1 = 1 + 1 = 2
COMANDO
0000 = LEER VALOR
0001 = RESP. VALOR
0010 = ESCR. VALOR
1010 = ESCR. MEM.
(B.S.)
4
CR
AA
AL
APT
AA
AA
CR = 2
CR = 4
AL
AL
CR = 5
AML
CR = 1
INCORRECTO
CR = 6
APT
AML
CR = 0
APT
= Contador de Ruta
= Acoplador de áreas
= Acoplador de líneas
= Aparato bus
1.1.2
ON
INSTALACIÓN ALICANTE
100%
1/1/1
-
1/1/1
1 bit
1 bit
INSTALACIÓN MADRID
1/1/1
1/1/1
4 bit
0 0 0 1
CAMPO DE CONTROL
1 0 1 1 1 1 0 0
K
N
X
R K P
E N R
P X I
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P
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A
M
B
U
L
O
DIRECCIÓN DE ORIGEN
DIRECCIÓN DE DESTINO
0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0
1
A
1
L
PRIO = 0 0 = SISTEMA
1 0 = ALARMA
ETS MOD. 
0 1 = ALTA
1 1 = NORMAL / BAJA
REP = 1 = NO
0 = SI
0 0 0 1
2
C8
D.U.
0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 1
1/1/1
T
I
P
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L
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TD = 1 = DG
0 = D.F. = D.I.
C
O
M
A
N
D
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L = LONG D.U. - 1
L + 1 = LONG D.U.
Ej. L = 1 = LONG D.U. - 1
LONG D.U. = L + 1 = 1 + 1 = 2
COMANDO
0000 = LEER VALOR
0001 = RESP. VALOR
0010 = ESCR. VALOR
1010 = ESCR. MEM.
(B.S.)
4
DATOS ÚTILES 1 BYTE
0
0
1
L
0
0
0
0
0
0
0
0
0
C
O
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A
N
D
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1
0
0
0
0
0
0
1
1
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0
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1
(B.S.)
1.1.2
ON
INSTALACIÓN ALICANTE
100%
1/1/1
-
1/1/1
1 bit
1 bit
INSTALACIÓN MADRID
1/1/1
1/1/1
4 bit
0 0 0 1
CAMPO DE CONTROL
1 0 1 1 1 1 0 0
K
N
X
R K P
E N R
P X I
O
P
R
E
A
M
B
U
L
O
DIRECCIÓN DE ORIGEN
DIRECCIÓN DE DESTINO
0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0
1
A
1
L
PRIO = 0 0 = SISTEMA
1 0 = ALARMA
ETS MOD. 
0 1 = ALTA
1 1 = NORMAL / BAJA
REP = 1 = NO
0 = SI
0 0 0 1
2
C8
D.U.
0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 1
1/1/1
T
I
P
O
CR
0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1
L
D
E
S
T.
TD = 1 = DG
0 = D.F. = D.I.
C
O
M
A
N
D
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L = LONG D.U. - 1
L + 1 = LONG D.U.
Ej. L = 1 = LONG D.U. - 1
LONG D.U. = L + 1 = 1 + 1 = 2
COMANDO
0000 = LEER VALOR
0001 = RESP. VALOR
0010 = ESCR. VALOR
1010 = ESCR. MEM.
(B.S.)
4
1.1.2
ON
INSTALACIÓN ALICANTE
100%
1/1/1
-
1/1/1
1 bit
1 bit
INSTALACIÓN MADRID
1/1/1
1/1/1
4 bit
0 0 0 1
CAMPO DE CONTROL
1 0 1 1 1 1 0 0
K
N
X
R K P
E N R
P X I
O
P
R
E
A
M
B
U
L
O
DIRECCIÓN DE ORIGEN
DIRECCIÓN DE DESTINO
0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0
1
A
1
L
PRIO = 0 0 = SISTEMA
1 0 = ALARMA
ETS MOD. 
0 1 = ALTA
1 1 = NORMAL / BAJA
REP = 1 = NO
0 = SI
0 0 0 1
2
C8
D.U.
0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 1
1/1/1
T
I
P
O
CR
0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1
L
D
E
S
T.
TD = 1 = DG
0 = D.F. = D.I.
C
O
M
A
N
D
O
L = LONG D.U. - 1
L + 1 = LONG D.U.
Ej. L = 1 = LONG D.U. - 1
LONG D.U. = L + 1 = 1 + 1 = 2
COMANDO
0000 = LEER VALOR
0001 = RESP. VALOR
0010 = ESCR. VALOR
1010 = ESCR. MEM.
(B.S.)
4
KNX PARTNER
TRAINING COURSE
KNX TP Telegram
KNX Association
KNX BASIC COURSE
Table of Contents
1
2
3
4
5
TP Telegram: general ................................................................................................ 3
TP Telegram structure ............................................................................................... 3
TP Telegram: time requirement ................................................................................. 4
TP Telegram acknowledgement ................................................................................. 5
Chapter telegram: “Informative annex” ..................................................................... 6
5.1
5.1.1
5.1.2
5.1.3
6
7
8
9
Numbering systems...................................................................................................... 6
Decimal system ............................................................................................................................... 6
Binary system .................................................................................................................................. 6
Hexadecimal system ........................................................................................................................ 6
TP Telegram: control field ......................................................................................... 8
TP Telegram: source address ..................................................................................... 9
TP Telegram: target address .................................................................................... 10
TP Telegram: check byte .......................................................................................... 11
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1
TP Telegram: general
Figure 1: TP telegram: general
When an event occurs (e.g. when a pushbutton is pressed), the bus device sends a telegram
to the bus. The transmission starts after the bus has remained unoccupied for at least the
time period t1.
Once the transmission of the telegram is complete, the bus devices use the time t2 to check
whether the telegram has been received correctly.
All “addressed” bus devices acknowledge the receipt of the telegram simultaneously.
2 TP Telegram structure
Figure 2: TP telegram: structure
The telegram consists of bus-specific data and the actual useful data, which provides
information about the event (e.g. pressing a push button).
The entire information is transmitted in the form of 8-bit long characters.
Test data for the detection of transmission errors is also included in the telegram: this
guarantees an extremely high level of transmission reliability.
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3 TP Telegram: time requirement
Figure 3: TP telegram: time requirement
The telegram is transmitted at a bit speed of 9600 bit/sec, i.e. one bit occupies the bus for
1/9600 sec or 104 µs.
A character consists of 11 bits. Together with the pause of 2 bits in between characters, this
adds up to a transmission time of 1,35 ms (13 bits) per character.
Depending on the length of the payload, the telegram consist of 8 to 23 characters, the
acknowledgement is only one character (11 bit). Taking into account the priority-dependent
waiting time of t1 (50 bits) and a time between telegram and acknowledgment t2 (15 bits), a
message will occupy the bus between 20 to 40 ms.
A switching telegram (including acknowledgement) occupies the bus for about 20 ms.
Telegrams for text transmission occupy the bus for up to 40 ms.
Example:
(t1 50 bit) + (8x13 bit) + (1x13 bit = CRC) + (t2 15 bit) + (Ack.11 Bit) = 193 bit
193 Bit x 0,104 ms = 20.07 ms
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4 TP Telegram acknowledgement
Figure 4: Telegram acknowledgement
The receiving bus device checks on the basis of the check byte contained in the telegram the
correct reception of information and acknowledges accordingly.
If a negative acknowledgement (NACK [transmission error detected] or BUSY [device unable
to process new information]) is received to a telegram sent on the bus, the sender will
repeat the telegram. The number of repeated telegrams is typically limited to three times.
This is also the case when an acknowledgement is missing.
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5 Chapter telegram: “Informative annex”
Figure 5: Numbering systems
5.1 Numbering systems
The terms ‘base’ and ‘digit’ are used in the classification of numbering systems.
In every numbering system, the largest digit is smaller than the base by 1.
5.1.1 Decimal system
This is the most common numbering system. People think in terms of decimal numbers. If
no details are given about the numbering system, the decimal system is assumed.
5.1.2 Binary system
This numerical representation is very important in computing as a storage location in
memory can only assume two states (0, 1). The content of such a storage location in
memory is called a bit.
5.1.3 Hexadecimal system
A combination of 4 bits of the binary system produces a hexadecimal number. This results in
a clearer representation of data.
Figure 6: Data formats
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Data formats
Different data formats are necessary for processing data. The contents of the data formats
can be presented in binary, decimal or hexadecimal form.
Number conversions
In order to be able to switch between the different numbering systems, values must be
converted.
Converting a binary or hexadecimal number into a decimal number
The number is split up into its individual powers, which are then added up.
e.g.: 0A9HEX = 0 x 162
+ 10 x 161 + 9 x 160
= 0 x 16 x 16 + 10 x 16
+9x1
= 169DEC
Converting a decimal number into a binary or hexadecimal number
The number is constantly divided by the base of the target numbering system (binary or
hexadecimal) until the original number equals zero. The remainder of each division form the
digits of the converted number, when read from back to front.
e.g.:
Division
Remainder
169 : 2 = 84
1
84 : 2 = 42
0
42 : 2 = 21
0
21 : 2 = 10
1
Reading order
10 : 2 =
5
0
5:2=
2
1
2:2=
1
0
1:2=
0
1
169DEC = 1010 1001BIN
Converting binary numbers into hexadecimal numbers
Often binary numbers can be converted more quickly if they are split into tetrads. Each
tetrad then corresponds to a number in the hexadecimal system. Leading zeros may be
added.
e.g.:
0000
1010
1001 BIN
0
A
9 HEX
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6 TP Telegram: control field
Figure 7: TP Telegram: control field
If one of the addressed bus devices has returned a negative acknowledgement and the
telegram transmission is repeated, the repeat bit is set to 0.
In this way, it is ensured that bus devices that have already executed the appropriate
command will not execute the command again.
The transmission priority is only observed if several bus devices attempt to transmit
simultaneously.
The required priority (apart from system priority) can be set for every group object using the
ETS. The standard setting is low operational priority.
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7 TP Telegram: source address
Figure 8: TP Telegram: source address
In the above example 3.10.20 represents the individual address of the bus device 20 in line
10 in area 3.
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8 TP Telegram: target address
Figure 9: TP Telegram: target address
The target address is normally a group address.
The target address can also be an individual address (system telegrams). On the basis of bit
17 the receiver can determine whether the target address is a group or individual address:
If the 17th = 0
The target address is an individual address. Only one bus device is
addressed.
If the 17th bit = 1
The target address is a group address. All bus devices with this address
are addressed.
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9 TP Telegram: check byte
Figure 10: TP Telegram: check byte
In order to detect errors in telegram transmission, test data is transmitted in the form of
parity bits (character check) and check bytes (telegram check).
Each character of the telegram is checked for even parity i.e. the parity bit P gets the value 0
or 1 to make the sum of all the bits (D0-D7 plus Pz) equal to 0.
In addition all characters of the telegram are checked for odd parity for each bit position, i.e.
the check bit S7 gets the value 0 or 1 to make the sum of all data bits D7 equals 1.
The combination of character check and telegram check is called cross check.
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700m
1.1.1
2/1/2
PAUSA
SP
P
7
6
5
2/1/2
1.1.4
< 10 μS
2/1/2
1.1.5
2/1/3
1.1.10
700m
350m
FA
TOTAL= 1000m
2
1
0
SP
I
1
1
1
0
1
1
1
1
0
0
0
I
1
0
0
0
0
1
0
0
0
1
0
I
1
1
0
0
0
0
0
0
0
1
0
I
1
0
0
0
0
1
0
0
0
1
0
I
1
1
0
0
0
0
0
0
1
0
0
I
1
0
1
1
1
0
0
0
0
1
0
I
1
0
0
0
0
0
0
0
0
0
0
I
1
0
1
0
0
0
0
0
0
1
0
I
1
1
0
0
1
0
0
0
0
0
0
B.S
C.C
1
0
0
0
A.C K
D.O 1.1.1
D.D. 2/1/2
? D.D. C.R. L.
D.U
13 BITS
I
350m
3
50 BITS
1.1.3
2/1/2
4
1
0
1
1
0
0
1
700m
1.1.1
2/1/2
PAUSA
SP
P
7
6
5
2/1/2
1.1.4
< 10 μS
2/1/2
1.1.5
2/1/3
1.1.10
700m
350m
FA
TOTAL= 1000m
2
1
0
SP
I
1
1
1
0
1
1
1
1
0
0
0
I
1
0
0
0
0
1
0
0
0
1
0
I
1
1
0
0
0
0
0
0
0
1
0
I
1
0
0
0
0
1
0
0
0
1
0
I
1
1
0
0
0
0
0
0
1
0
0
I
1
0
1
1
1
0
0
0
0
1
0
I
1
0
0
0
0
0
0
0
0
0
0
I
1
0
1
0
0
0
0
0
0
1
0
I
1
1
0
0
1
0
0
0
0
0
0
B.S
C.C
1
0
0
0
A.C K
D.O 1.1.1
D.D. 2/1/2
? D.D. C.R. L.
D.U
13 BITS
I
350m
3
50 BITS
1.1.3
2/1/2
4
1
0
1
1
0
0
1
KNX PARTNER
TRAINING COURSE
KNX Bus Devices
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Table of Contents
1
2
3
4
Introduction .............................................................................................................. 3
Internal structure of a Bus Coupling Unit ................................................................... 5
Type definition of an application module................................................................... 8
Overview of the most important KNX standardised system profiles............................ 9
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
5
Access control ............................................................................................................................... 10
Serial number ................................................................................................................................ 10
Interface objects............................................................................................................................ 10
Memory size .................................................................................................................................. 10
Classical application functions ................................................................................. 11
5.1
5.2
5.3
5.4
5.5
6
System profiles ............................................................................................................ 9
Detailed description of the above features ................................................................. 10
Dimming with start/stop telegram ............................................................................. 11
Dimming with cyclical telegrams ................................................................................ 12
Application function: 'dimming actuator' .................................................................... 13
Application function: drive control sensor .................................................................. 14
Application function: drive control ............................................................................. 15
Drive control object structure .................................................................................. 16
In this chapter the following abbreviations are used:
PEI = Physical External Interface
BCU = Bus coupling unit
AM = Application module
TRC = Transceiver
SR = Shift register
DAC = Digital-Analogue Converter
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1 Introduction
KNX
Bus device
BCU
AM
AM
PEI
Figure 1: Bus device
A functioning bus device (e.g. dimming/shutter actuator, multi-functional push button, fire
detection sensor…) principally consists of three interconnecting parts:
 bus coupling unit (BCU)
 application module (AM)
 application program (AP)
Bus coupling units and application modules are offered on the market either separated or
built into one housing. They must however always be sourced from the same manufacturer.
When separated, the application module can be connected to the BCU via a standardised or
a manufacturer-specific Physical External Interface (PEI). This PEI serves as
 an interface to exchange messages between both parts
 the power supply of the application module
Whether the application module and bus coupling unit fit together – also whether they can
be connected mechanically – has to be checked with the respective manufacturer. In case of
TP devices, the connection to the bus is mostly ensured via the standardised bus connector
(dark grey/red). In case of DIN rail devices, connection to the bus is sometimes also ensured
via contact blocks to a so-called data rail (see chapter “Installation”).
When the BCU is an integrated part of the bus device, it is takes either the shape of a BIM
(Bus Interface Module) or a chip set. A BIM is a bus coupling unit without programming
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button and LED (these are added to the application module). A chip set consists of the core
of a BIM, i.e. the controller and the transceiver1.
BCUs are currently available for connection to three different media: Twisted Pair (Safety
Extra Low Voltage), Powerline 110 (mains power) and RF (KNX-RF). The classical bus coupling
unit contains apart from the physical coupling function (sending and receiving bus
telegrams), also the application program memory. Newer developments are however also
available that only assume the task of sending and receiving bus telegrams. The
“intelligence” or the operating system and application program are in this case an
integrated part of the application module.
Each bus device has its own intelligence thanks to the integrated operating system and
program memory in the BCU or in the application module: This is the reason why KNX is a
decentralised system and does not need a central supervising unit (e.g. a computer). Central
functions (e.g. supervision) can however if needed be realized via visualisation and control
software installed on PCs.
Depending on their main function, bus devices can basically be divided into three classes:
sensors, actuators and controllers. It is rare to have devices with pure sensor or actuator
functionality nowadays. E.g. each push button with LED status display also has an “actuator”
function and each actuator with status information has a “sensor” function.
 In the case of a sensor, the application module transfers information about its actual
inputs (digital / analog) to the BCU. The latter codes this data and sends it on the bus.
The BCU therefore regularly checks the state of the inputs of the application module.
 In the case of an actuator, the BCU receives telegrams from the bus, decodes them and
passes this information on to the application module, which then controls the actual
available outputs (digital / analog).
 A controller regulates the interaction between sensors and actuators (e.g. logical
module) and has no physical inputs and outputs.
In the case of S-mode compatible KNX devices, a device receives its predetermined function
once the appropriate application program for the application module has been loaded into
the program memory (via the ETS). An S-mode compatible KNX push button mounted on
a BCU can only generate dimming signals, after the suitable application program has been
programmed into the device via the ETS.
In the case of E-mode compatible KNX devices, a device is normally shipped with loaded
application program. The linking of such KNX devices and the setting of the relevant
parameters is either ensured via appropriate hardware settings or via a central controller.
1 This can be a discrete solution, an ASIC or in case of TP, the so called TP-UART.
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2 Internal structure of a Bus Coupling Unit
(Flash)ROM: System software
RAM:
Current values
EEPROM:
Application program,
addresses, objects, parameters
-
Black
PEI
RAM
(Flash)ROM
Red
+
TRC
EEPROM
µP
µC
KNX
+
-
Figure 2: Internal structure of a bus coupling unit
There are two types of KNX bus coupling units:
 A BCU with program memory (microcontroller and a transceiver suitable for the
connected medium) and with PEI to the AM.
 A BCU without program memory (only a medium specific transceiver with digital
interface to the application microcontroller)
In the different types of a memory of the microcontroller, the following data is stored:
 The system software: the different standardised KNX system software profiles (also
referred to as “system stack”) are identified by their “mask version” or “device
descriptor type 0”. A mask cannot be changed. The mask version consists of 2 bytes
where:
 The first digit y refers to the corresponding medium – 0 for TP, 1 for PL110, 2 for RF
and 5 for KNXnet/IP. Not all software profiles are available on all before-said media.
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 The last digit x refers to the current version of the software profile.
ETS is informed about the underneath mentioned system profiles through the
following mask versions:
o
o
o
o
o
o
o
o
o
y01xh: System 12
y02xh: System 23
y70xh: System 74
y7Bxh: System B
y300h: LTE
091xh: TP Line/backbone coupler – Repeater
190xh: Media coupler TP-PL110
2010h: RF bi-directional devices
2110h: RF unidirectional devices
Unidirectional devices can basically not be configured by ETS. Only e.g. gateways which
communicate with these devices can be configured by ETS. Bi-directional RF-BCUs can be
configured since the introduction of ETS 5.
 Temporary values of the system and the application: These are lost when there is a bus
power down (if not stored earlier in non-volatile memory by the device).
 the application program, the physical and group addresses: these are usually stored in
memory that can be overwritten.
In the case of S-mode compatible devices, the manufacturer makes the application program
available to the installer as an ETS product entry, who then loads it into the device. The
manufacturer code of the application program and the bus coupling unit must match to be
able to load the application program.
In the case of E-mode devices, the device reports the supported functionality (as regards
supported “Easy” channels) by means of the device descriptor 2.
2 previously referred to as BCU 1
3 previously referred to as BCU 2
4 previously referred to as BIM M 112
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-
Red
Black
+
Save
< 18 V
20 V
RPP
20 V
5V
5V
µC
< 4,5 V
Reset
0V
Driver
Logic
Receive
Send
Enable
KNX
+
-
Bus Coupling Unit
Figure 3: Transceiver
The TP transceiver has the following functions:







Separation or superimposing of the direct current and data
Reverse voltage protection (RPP)
Generation of stabilised voltages of 5 V DC respectively 20 V DC
Initiating a data back-up if the bus voltage drops below 18 V
Triggering a processor reset if the voltage drops below 4,5 V
Driver for transmitting and receiving
Sending and receiving logic
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3 Type definition of an application module
BCU
PEI
Analogue
6
AM
R-Typ
+5 V
2
3
Data
4
7
9
1/10
0V
+5 V
+20 V
5
+5 V
8
+20 V
Figure 4: Type definition of an application module
Via a resistor (R-Type) in the application module, the bus coupling unit is able to detect via
pin 6 of the PEI, whether the application module mounted on the BCU fits to the loaded
application program. When the R-Type does not correspond to the one indicated in the
application program, the BCU automatically halts the application program. However, this
rarely applies to more recent bus devices, as for products without a PEI and with a fully
integrated BCU, such a check is no longer required. So, consequently such a PEI check is
mainly limited to flush-mounted bus coupling units. The underneath table gives an overview
of the principal PEI types.
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4 Overview of the most important KNX standardised system
profiles
4.1 System profiles
A system profile can be compared to the operating system of a PC.
The System 1 technology was introduced with the first generation of KNX devices (in 1991),
but which is still available. A few years later products based on System 2 and System 7 were
introduced. System 7 was then further developed to System B in order to get rid of the
limitations with regard to the number of group objects and group addresses. The table
below gives an overview of the most important features of these KNX system profiles:
Mask version
Maximum number of group objects5
System 1
System 2/7
System B
E.g. 0012h
E.g. 0025h, 0705h
E.g. 07B0h
12
254
65536
Support of interface objects
Support serial number
No
Yes
Support access control
5 The actual number of available group objects or group addresses which can be assigned depends on the used
microcontroller
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The System 7 technology is especially intended for more complex bus devices, which assume
centralised functions (e.g. application controllers, gateways...).
Application programs designed for System 1 technology can also be loaded into certain
System 2 devices (upwards compatibility).
4.2 Detailed description of the above features
The features of System 2, System 7 and system B outlined above are explained here again in
detail:
4.2.1 Access control
When a tool wants to access memory of System 2, 7 and B devices (reading and/or writing),
it must first get authorisation by means of an authorisation key of 4 byte.
A manufacturer can define keys for such devices: however some of these are reserved for
access to system relevant memory (amongst others the highest access key 0) and are
therefore not communicated to the customers.
The ETS can apply these access mechanisms for not system related memory in the devices
with the before-mentioned system profiles. Access control is never needed for normal
communication via group addresses. In this case, access is always possible.
4.2.2 Serial number
System 2, 7 and System B devices use a serial number: this number, which is assigned to
each device before leaving the factory, allows writing or reading the individual address of a
device without having to press the programming button of the device. This feature is
however not yet supported in ETS.
4.2.3 Interface objects
Interface Objects contain certain system and application properties (e.g. address table,
parameters …), which can be read and/or written by a tool (e.g. ETS during download)
without explicit knowledge of the device’s memory map. The ETS end user cannot
manipulate such objects but can read them by means of the ETS “Device Editor” App. More
in-depth system knowledge explained during the tutor course is required in order to do this
kind of manipulation.
4.2.4 Memory size
When looking at the number of group objects and group addresses one can see that the
memory size increases with the listed mask version: the memory of system 2 is bigger than
1, and 7 is bigger than 2, especially for profile “B”. For more than 10 years, 255 group
objects were considered as a large number but with the development of new touch panels,
application controllers and gateways this number became too small again. That is why
system 7 was extended with 1 byte as regards number of addresses and objects. Because of
this, 65536 and 65535 have now become the maximum values, normally not reached by
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current applications. In other words, this is s a pure theoretical value, especially when one
compares this to the total possible address capacity of a KNX system (which is just as big).
5 Classical application functions
5.1 Dimming with start/stop telegram
DIMMING ACTUATOR SWITCHES TO LAST REACHED VALUE (PARAMETER DEPENDENT)
100%
0%
START DIMMING
LONG OPERATION
STOP DIMMING
RELEASE DIMMING
ROCKER
SWITCH OFF
SHORT OPERATION OF
ROCKER
SWITCH ON
START DIMMING
SHORT OPERATION OF
LONG OPERATION
ROCKER
STOP DIMMING
RELEASE ROCKER
Figure 5: Dimming with start/stop telegram
The duration of the rocker operation determines whether the switching function or the
dimming function via the same rocker is activated. If the time the rocker is pressed is
shorter than the time parameterized in the application program of the push button (e.g. <
500 ms), a switch telegram is transmitted. If one operates the rocker longer than the time
parameterized, a 'start dimming' telegram is transmitted. As soon as the rocker is released
again, a 'stop dimming' telegram is transmitted.
Different group addresses are used for the switching and dimming telegrams to ensure that
the dimming actuator executes the correct functions.
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5.2 Dimming with cyclical telegrams
DIMMING SPEED OF THE ACTUATOR SHALL BE ADAPTED TO THE CYCLICAL TRANSMISSION OF DIMMING TELEGRAMS
Brightness
100%
7/8
6/8
5/8
4/8
3/8
2/8
1/8
+ 12,5 %
+ 12,5 %
+ 12,5 %
+ 12,5 %
+ 12,5 %
+ 12,5 %
+ 12,5 %
+ 12,5 %
Time
Figure 6: Dimming with cyclical telegrams
In a system controlled by wireless remote controls, e.g. infrared senders, the transmission
signal might be interrupted as somebody passes through the IR beam. In order to avoid a
situation where the dimming actuator does not receive important telegrams (e.g. the stop
telegram), in most cases one will choose the setting 'cyclical dimming' during
parameterisation of a remote control. The transmitter in these settings transmits the
telegram “increase brightness by 12,5 %”. The consequences of losing such a telegram are
not as serious as the loss of a stop telegram, which is only sent once.
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5.3 Application function: 'dimming actuator'
PEI
230 V AC
SR
0 – 10 V
DAC
20 V
5V
BCU
AM
Dimming
Electronic
ballast
Figure 7: Application function: 'dimming actuator'
The counterpart to the sensor function dimming is the dimming actuator. There are various
types of dimming actuators, depending on the dimming concept and the lamps or the
ballasts used. In this example a passive 1 – 10 V analogue interface is shown. But all
dimming actuators have something in common: They have a parameterized dimming speed.
The dimming speed is therefore an exclusive matter of the actuator!
In the example shown above, the BCU transmits a control signal to the application module.
This signal has to be electronically adapted to the control input of the electronic ballast. The
dimmer's electronic ballast uses the voltage to control the light emission of a fluorescent
tube. The relay in the application module is used to (dis)connect the mains voltage.
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5.4 Application function: drive control sensor
Release rocker
Start operation of rocker
PEI
Brief operation of
rocker
Up
t1
Down
Slats 1. level Open/Close
Telegram
Long operation of
rocker
t2
Blinds
Up/Down
Telegram
Operation of rocker > Parameterized time
t
BCU
AM
Figure 8: Application function: drive control sensor
The blinds but also the shutter operation functions similarly to the dimming operation: A
distinction is made between a brief and a long operation of the rocker.
The time t2 (e.g. 500 ms) acts as a "boundary" between the commands “slats step
open/close” and “blinds up/down”.
T1 is the debouncing time that can be set for push button interfaces and binary inputs. For
push buttons there is normally no debouncing time.
An important difference with dimming is however that if one releases the rocker once the
drive has started, the drive will continue to work until one has again shortly presses the
rocker.
This makes sense as blinds / shutters have basically much longer travel times compared to
the time a dimming actuator needs for to dim up to 100%.
The short operation of the rocker has also two different implications – when the drive is not
in motion, it will cause a moving of the slats (only meaningful for blinds with adjustable
slats). When sending the step command to a moving drive, this will cause the drive to stop.
This shows that in any case for blinds control both commands i.e. shorter or longer
operation of rocker are required, also when there is no need to adjust the slats.
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5.5 Application function: drive control
PEI
24 / 230 V AC
S1
S2
AM
BCU
M
Figure 9: Application function: drive control
Depending on the telegram received, the BCU passes on the command “up” or the
command ”down” to the relay S2. On receiving the telegrams “slats open/close 1 step”', the
BCU energises the relay S1 for the appropriate duration. If the motor was already switched
on, this telegram halts the blind (S1 opens). On receiving the telegram “blinds up/down”,
the BCU energises the relay S1 for a period longer than the total time the blind is in
movement from the very top until the very bottom and vice versa. As usual, the limit
switches of the blinds bring the motor to a halt when the limit position is reached, even if
there is still voltage at the motor.
A blind actuator never has the task to take care of the safe deactivation of the blinds. This
always needs to be ensured by the device itself in order to guarantee interlocking!
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6 Drive control object structure
Telegram from:
Automatic Group 2/1/31
Push button Group 2/1/12, 2/1/13
Wind sensor Group 2/1/99
Group object table
2/1/99
2/1/31
2/1/13
2/1/12
Object 1
SAFETY
Telegram gale:
Blinds control disabled
Blinds e.g. Up
Object value = 1
Object 2
UP / DOWN
Object 3
SLATS
Telegram blinds
Up / Down
(Long operation)
Telegram slats
Up / Down
(Short operation)
Gate: Open when 0
Gate: Open when 0
Telegram gale end:
Control enabled
Object value = 0
Object value = 1:
Up
Disable normal operation
Execution
Figure 10: Drive control object structure
The figure above shows the basic functionality of a blind actuator. Apart from the normal
operation each blind/shutter actuator can for instance have a safety function.
If, for example, the sensor responsible for measuring the position of the sun triggers the
telegram “blinds down” using the group address 2/1/31, the object group "up/down" is
addressed and the corresponding command is executed.
Brief operation of the push button transmits the 2/1/13 telegram “adjust slats” and long
operation of the key sensor sends the 2/1/12 telegram “open/close blinds completely”.
Telegram 2/1/99 triggered by the wind sensor addresses the object group “safety”. If a gale
is developing, telegram 2/1/99 orders the blinds to go up/down (depending on the
parameterization) and disables any further operation. When the storm has eased off, a
telegram is sent that enables blind operation again. The de-activation of the alarm does not
mean that the actuator is lowering the blinds again by itself (in the position before the gale).
This makes no sense as the actuator has no information about the duration of the alarm or
whether the blind really has to go down again.
New actuators have of course a variety of further functions and group objects, which cannot
be explained during the basic course due to time constraints. These more complex
functionalities, e.g. weather station, are explained in detail in the advanced course.
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Futurasmus Zentrum
KNX++ TRAINING CENTER
C/ de la Nit. 1, Bloque 7, Local 1 03110
Mutxamel (Alicante)
T: +34 965959511
E: info@futurasmus-knxgroup.com
www.futurasmus-knxgroup.org
t = 0 seg
ON / +
t corta / larga = 0,5 seg
1/2/1 = 1
1 bit
1/2/1
4 bit
1/2/2
1/2/2 - 9
1/2/2 - 8
1/2/2 - ‘1’
1/2/2 - ‘0’
1/2/1 = 0
OFF / 1 bit
1/2/1
4 bit
1/2/2
1/2/1
1/2/2
1/2/3
1 bit
4 bit
1 byte
t = 0 seg
t = 0,5 seg
t corta / larga
t2
1/3/1 STOP / LAMAS
1/3/1 = 0
/ STOP
1/3/2 MOVIMIENTO
X
t MOV = 30 seg
t LAMAS = 0,3 seg
t CAMBIO SENTIDO = 0,5 seg
‘0’
1/3/1
1/3/2
1/3/1 = 0
1/3/2 = 0
X
1/3/1 = 0
1/3/1 = 1
Fase
X
/ STOP
‘1’
1/3/1
1/3/2
1/3/1 = 1
1/3/2 = 1
X
N
1/3/1 = 1
M
KNX PARTNER
TRAINING COURSE
KNX TP Installation
KNX Association
KNX BASIC COURSE
Table of Contents
1
2
3
4
5
6
7
Safety Low Voltage Networks .................................................................................... 3
SELV Safety Extra Low Voltage Network .................................................................... 4
Types of Bus cable ..................................................................................................... 5
Installation of cables ................................................................................................. 7
Bus Devices in distribution boards ............................................................................. 8
Power supply unit...................................................................................................... 9
Power supply for two lines ...................................................................................... 11
7.1
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Two power supply units in one line............................................................................. 12
Distributed power supply ........................................................................................ 13
Bus cables in wall boxes .......................................................................................... 14
Installation of flush-mounted bus devices ................................................................ 15
Standardised TP Bus connector ................................................................................ 16
Lightning protection measures ................................................................................ 17
Bus cables installed between buildings .................................................................... 19
The prevention of loops ........................................................................................... 20
Basic immunity of bus devices ................................................................................. 21
Bus devices on cable ends ........................................................................................ 21
The overvoltage arrester terminal ........................................................................... 22
Recommendations to the use of overvoltage arresters ............................................. 23
Checking the installation ......................................................................................... 24
Information to the use of data rails ......................................................................... 26
Power supply unit with data rail .............................................................................. 27
Power supply unit for two lines with data rail .......................................................... 28
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1 Safety Low Voltage Networks
SELV (Safety Extra Low Voltage)
 Safety transformer
 Voltage range less than/
identical to 120 V DC or 50 V AC
 Safe insulation to e.g.
230 / 400 V AC
 SELV may not be earthed!
Figure 1: Safety Low Voltage Networks
General: for the bus and mains installation the relevant installation requirements of the
respective country shall be observed.
SELV stands for Safety Extra Low Voltage
Clearance and creepage distances: The clearance and creepage distances indicated above
apply for:
 Pollution degree 2 (offices)
 Overvoltage category 3 (permanently connected to mains, high availability)
 Insulation material class 3
Permitted voltage range:
 Alternating current (AC):  50 V
 Direct current (DC):  120 V
No special protection against direct contact is required if the voltages do not exceed 25 V AC
or 60 V DC.
Earthing:
 A SELV network may not be earthed!
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2 SELV Safety Extra Low Voltage Network
User
No insulation
Mains network
230 / 400 V
SELV – Network
for KNX: 30 V DC
Other networks
E.g.
telecommunication
PE
Safe insulation
Basic insulation
Figure 2: SELV Safety Extra Low Voltage Network
A power supply with secure mains separation generates the SELV voltage for the KNX TP
bus.
Voltage used:
 30 V DC
Insulation:
 Safe insulation from other networks.
 Basic insulation to earth.
 No insulation on the user’s side.
Attention:
 The SELV network may not be earthed!
 Cables that are intended for the installation of mains networks may not be used for the
installation of TP networks!
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3 Types of Bus cable
YCYM 2×2×0,8
- Fixed installation: dry, humid and wet rooms; wall-mounted, flush-mounted, in conduits;
- Outdoor: If protected against direct sun radiation;
- Test voltage: 4 kV according to EN 50090
J-Y (St) Y 2×2×0,8
- Fixed installation: dry and humid industrial sites; wall-mounted, flush-mounted, in conduits;
- Outdoor: Flush-mounted and conduits
- Test voltage: 2,5 kV according to EN 50090
Synthetic Material
Tracer
- (white)
KNX
+ (yellow)
- BUS (black)
Synthetic foil
Metalised synthetic foil
+ BUS (red)
Figure 3: Types of bus cable
Cable fulfilling the KNX requirements in volume 9 of the KNX Specifications (e.g. YCYM
2×2×0,8 or J-Y(St)Y 2×2×0,8 in TP design) can be approved (without KNX logo) or certified
(with KNX logo) by KNX Association1.
Only the standard green KNX TP cable guarantees:
 max. cable length of a line
 max. distance between two bus devices in a line
 max. number of bus devices per line
The requirements for instance include a loop resistance of 75  and a loop capacitance of
100 nF per 1000 m. For all other cables types, the maximum length given in the data sheet
of the cable must be observed.
Normally, it is not necessary to connect the shielding of the cables.
1 For the current list of KNX certified/approved cable types, please consult the KNX web site (www.knx.org)
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When installing a standard cable with a test voltage of 4 kV, the following conditions apply.
Used wire pair:
 Red: plus
 Black: minus
Spare wire pair: Permitted use of the spare wire pair:
 no connection at all
 for other SELV low voltage networks
Test voltage according to EN 50090:
The specified test voltage must be applied to all connected wire cores (shielding drain wire
included) and the outer surface of the cable sheath.
Note:
Please make sure that all installed cables are properly identified and marked!
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4 Installation of cables
230 V e.g. NYM
Overall insulated single core
230 V adjacent to the sheath of
the bus cable
KNX TP
YCYM or J-Y(St)Y (2,5 kV)
KNX TP
YCYM or J-Y(St)Y (2,5 kV)
*
Overall insulated single core of
the bus adjacent to the sheathed
mains cable
230 V e.g. NYM
230 V e.g. NYM
KNX TP
*
Exposure of two single cores
YCYM or J-Y(St)Y (2,5 kV)
>= 4 mm separation or
*identical insulation
Figure 4: Installation of cables
The requirements for the installation of bus cables are generally the same as for the
installation of 230/400 V AC networks.
Special requirements:
 Insulated wire cores of sheathed mains cables and KNX TP bus cables may be installed
next to each other without any clearance space.
 A minimum clearance space of 4 mm must be observed between the insulated wire
cores of KNX TP bus cables and those of sheathed 230 V AC mains cables. Alternatively,
the wire cores must be provided with an equivalent insulation, such as a spacer or
insulation sleeving. This also applies to wire cores of other cables that are not part of
SELV/PELV circuits.
 An adequate distance to the external lightning protection system (lightning arrester)
must be ensured.
 All cables should be permanently marked as KNX TP or BUS cables.
A terminating resistor is not required.
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5 Bus Devices in distribution boards
Standardised power
distribution boards
Requirements
50 U
 Use of standardised distribution
boards
 Install bus cables with sheath up to
the terminal
 Do not install bus devices above mains
devices with significant power losses
 Cover unused section of data rail
Figure 5: Bus devices in distribution boards
Any commercial, standardised electric power distribution board equipped with EN 50022
35x7.5 mm DIN rails may be used, on which KNX TP DIN rail mounted devices can be
mounted.
Some of these KNX TP DIN rail mounted devices use spring contact blocks to a standard data
rail glued into DIN rails, others have the normal bus connector (see below) for connection to
the bus.
When using data rails unused parts of the data rail must be protected by cover strips.
If the mains section is separated from the bus installation, no special installation
requirements need to be observed.
If the mains section is not separated from the bus installation, the bus cables must be
sheathed up to the terminals.
Possible contact between mains cores and bus cable cores must be prevented by adequate
wiring and/or mounting.
Bus devices should not be mounted above mains devices with significant power losses, as
this could cause excessive heat development in the installation.
When a lightning arrester is installed on a DIN rail containing a data rail, the following
requirements must be met:
 Overall insulation of the arrester (e.g. no use of uncovered air spark gaps).
 As DIN rails may not be used for earthing, arresters must have a separate earthing
terminal.
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6 Power supply unit
TP Connector
DVC
>= 21 V DC
DVC
>= 21 V DC
230 V
50/60 Hz
Power supply unit / Choke
30 V DC 640 mA
Bus line
> 100 ms
buffer
Figure 6: Power supply unit (with TP connectors)
Note: if not explicitly said below, the following applies to centralised power supply units.
Power supply units produce and monitor the system voltage of 30 V DC necessary for the
operation of a KNX TP installation.
Each line needs an own power supply unit to supply the connected bus devices.
The power supply unit has an integrated voltage and current control and is therefore
resistant to short circuits.
The power supply unit is able to bridge short power gaps of minimum 100 ms.
Bus devices require a minimum of 21 V DC for safe operation. The energy demand of the
device can be read in the data sheet of the respective manufacturer.
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Features
Example of a power supply unit
 Earth connection prevents static
charging
230 V
L
DIN-Rail
N
Mains
Technical information
230 V
50...60 Hz
Power Supply Unit
 100 ms buffer time bridges brief
interruptions of the mains
 Optional LEDs for displaying
Overload
Mains
Overvoltage
Overload
Mains
Overvoltage
30 V DC
0...45 °C
Ancillary voltage
KNX voltage
 Additional output for supplying other
line (needs extra choke !)
Figure 7: Example and features of a power supply unit (on DIN rail without data rail)
To prevent from static charges on the bus side, the power supply unit includes high ohmic
resistances connected from each bus core to earth. The power supply unit should be
earthed. To do so, connect the earth point of the low voltage installation to the power
supply unit. This connection should be marked yellow/green. This does not result in
protective effects according to safety regulations and does not contradict the conditions
that apply for SELV networks.
Some power supply types or external chokes have a reset switch and a red control LED. The
connected line can be set to 0 V with this switch. The chokes prevent the short-circuiting of
bus telegrams (alternating voltage 9600 Hz) by the DC controller of the power supply unit.
Many types of power supply units are available, depending on the supplied output current
(160 mA, 320 mA, 640 mA). It goes without saying that the number of installable devices in a
line depends on the type of PSU used and the individual power consumption of the devices
in that line. Some PSU types have an integrated choke; some need an additional external
choke.
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Modern power supply units are DIN rail mounted, whereby the bus voltage is available via
an included bus connector. Some types have an ancillary voltage output, with which it is
possible to supply other lines using a separate choke. Uninterruptible power supply types
are also available. Some PSU types have a floating relay output providing information about
normal operation/mains failure for evaluation purposes. Most of the PSU types have LEDs,
indicating the operating mode of the power supply unit e.g.
 Green: The power supply is active.
 Red: The power supply unit is overloaded, possibly due to a short circuit between bus
wires.
 Yellow: An external voltage higher than 30 V has been applied to the bus side.
7 Power supply for two lines
230 V
50/60 Hz
Power supply unit / choke
30 V DC 640 mA
Choke
> 100 ms buffer
White
Line 2
Yellow
Line 1
Figure 8: Power supply for two lines (DIN rail without data rail)
If additional current is needed and depending on the load, one power supply unit can feed
two lines. An additional choke may be required depending on the type of power supply unit.
The bus voltage is available via the dark grey/red bus connector and the ancillary power via
a white/yellow connector.
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7.1 Two power supply units in one line
DVC
DVC
DVC
DVC
DVC
DVC
DVC
KNX
Ps / Ch
Ps / Ch
Minimum distance between power
supplies as specified by the manufacturer
Figure 9: Two power supply units in one line
If more than 30 bus devices are connected at a short distance from one other (e.g. in a
distribution board), the power supply unit should be installed in the vicinity of this group of
devices.
If an additional power supply unit needs to be installed, the minimum distance between the
two power supply units shall be taken from the power supply unit specifications of the
manufacturer.
It is not allowed to have more than two power supply units in one line.
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8 Distributed power supply
Figure 10: Cable length
In this case, instead of a centralised bus power supply, the bus is powered in a distributed
way by of the some devices connected to the line containing each of them a Decentralised
Power Supply Unit (DPSU) with integrated choke module. Stand-alone DPSU (noncommunicating) devices are also possible.
A DPSU is especially intended for small installations with few devices.
Different types of DPSU exist, depending on the supply current (25, 40 and 80 mA).
In most cases, it is possible to combine DPSU with up to two standard central PSUs.
The DPSU can be located at any point in the bus line. There are no limitations concerning
minimal distances between two DPSUs or a DPSU and a standard central PSU.
Up to eight DPSUs can be mounted in one single bus line. More than eight can have a
negative effect on communication. In case of mounting up to 8 DPSUs in a single line
together with a central PSU, the maximum resulting short circuit current of these devices (as
given in the product data sheet and/or ETS database) shall not exceed 3 A.
In most cases it is possible to manually disable the DPSU on the device (e.g. by jumper or
configuration of a parameter).
The cable length that needs to be observed in conjunction with the use of central and
decentralised power supply units is given in the above figure.
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9 Bus cables in wall boxes
Mains and bus wires should be installed either in:
 Separate installation / wall junction boxes or;
 Common installation boxes with a partition, guaranteeing the required clearance / creepage
distances
Figure 11: Bus cables in wall boxes
SELV circuits require double or reinforced insulation (protective separation) between mains
and bus cables, i.e. unsheathed bus cable cores should never be in contact with mains
cables. Junctions can be installed:
 in separate boxes or
 in a common box with a partition, ensuring 5,5 mm clearance and creepage distances
e.g. towards 230 V / 400 V AC TN/TT networks in office buildings.
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10 Installation of flush-mounted bus devices
Area
Area
230 / 400 V
Line
Device
Line
Device
 Use of wall boxes for screw mounting
 Permitted use of flush-mounted devices in combination with mains devices depends on the
environmental conditions and the design of the bus devices (e.g. pollution degree, overvoltage
category).
Figure 12: Installation of flush-mounted bus devices
Only wall boxes suitable for screw mounting may be used. Clamp mounting is in most cases
not possible.
In order to provide sufficient room for cables, wall boxes with e.g. a depth of 66 mm should
be installed.
“Combinations” refer to the use of mains devices (e.g. socket outlets) and bus devices (e.g.
push buttons) or other electric circuits underneath a common cover.
Both components must be safely insulated from each other. This can be achieved by using
basic insulation for the power devices and basic 230 V insulation for the bus device.
Do not forget to enquire with the manufacturer of the bus device whether this particular
device may be installed together with power devices.
Please note:
 The installation of a bus device in combination with power devices must be explicitly
approved by the manufacturer of the bus device!
 The manufacturer may specify certain bus installation requirements, which must be
strictly observed (e.g. connection of the frame to the protective earth conductor).
 Mains devices must at all times be protected against accidental contact, even when the
common box cover is removed.
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11 Standardised TP Bus connector
Bus connector
Usage
 Joints, extensions or connections are realised by means of
bus connectors
 Bus cable shall only end either at the device itself or at this
terminal
 Removal of bus devices without interrupting the bus
 Mechanical protection against reverse polarity
Figure 13: Bus connector
The bus connector is used for




branching the bus cable
extending the bus cable
protecting the bus cable ends
connecting the bus cable to bus devices
To avoid confusion with other electrical circuits, the bus connector should only be used for
KNX TP.
The bus connector consists of two parts:
 the plus part (red) and
 the minus part (dark grey)
which are mechanically linked by means of a dovetail joint. Up to four bus wires (6 mm
stripped) can be connected to each part by means of screwless terminals.
Standardised TP bus connectors allow the removal of bus devices without interrupting the
bus line.
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12 Lightning protection measures
Figure 14: Lightning protection measures
The KNX TP bus network should be integrated into the protection measures of the mains
power network.
The need for lightning protection for buildings may be the result of:
 the local building regulations;
 a risk analysis of the construction (e.g. in Germany according to EN 62305)
 a requirement from an insurance company.
In general, lightning protection measures are required for buildings that can be easily struck
by lightning or to which lightning can inflict heavy damage. These especially include
conference rooms, public buildings etc.
The internal lightning protection constitutes the most indispensable part of a lightning
protection system. Its most significant component is the lightning protection equipotential
bonding bar.
All conducting elements or systems, such as the water supply system, gas pipes, central
heating system, metal walls, etc. must be connected to the equipotential bonding strip
(EBS). In the currently valid guidelines (EN 62305, IEC 1024-1, IEC 61312-1), the lightning
protection equipotential bonding strip is a binding requirement also for active conductors;
they must be indirectly connected by means of lightning surge arresters. This is referred to
as ‘primary protection’.
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Primary protection is achieved by using:
 For the 230/400 V AC mains:
 nominal discharge current at least 12,5 kA (10/350 µs) per conductor
 protection level: < 4 kV
 Surge protection device (SPD) Type 1 according EN 61643-11:2012
 For the bus line
 nominal discharge current at least 2,5 kA (10/350 µs) per conductor
 protection level: < 600 V
 Surge protection device (SPD) Category Type 3 according 61643-11:2012
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13 Bus cables installed between buildings
Figure 15: Bus cables installed between buildings
If lightning protection measures have been installed, special measures must be taken if the
installation contains bus cables that extend over more than one building. It is recommended
to take these measures even if such lightning protection systems are not installed.
Either a lightning current arrester should be installed at the next corner of the building
(which should be connected to the main equipotential bonding), or the bus cable should be
installed in-between the buildings in a metal conduit or duct, which should be connected to
earth on both sides, at the entrance to the building. In order to discharge parts of the
lightning current, a minimum cross-sectional area of 16 mm2 CU or 25 mm2 Al or 50 mm2 FE
is required according to EN 62305-3.
In either case, the connected bus devices in the building should be connected to an
overvoltage arrester terminal for secondary protection. The bus devices and the overvoltage
arrester terminal should be mounted apart at a distance of some (cable) metres to make
sure that the overvoltage arrester terminal is not forced to accommodate parts of the
primary protection.
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14 The prevention of loops
230 V AC
Water pipe
Bonding Bar
Power
supply
Power
supply
Bus
Bus
DVC
Loop between bus – 230 V AC
Consisting of DVC and power supply
DVC
Loop between bus – water supply system
consisting of DVC, power supply and
bonding bar
Figure 16: Prevention of loops
As a consequence of the impact of lightning, major overvoltages are generated in loops,
which can cause flash-overs in bus devices. The larger the loop area, the larger the (peak)
overvoltage to be expected.
Loops are created when for instance both the bus cable and the 230 V cable are connected
to one bus device, as in this case also the power supply unit is connected to both networks.
Both devices are therefore at risk when struck by lightning.
However, loops are also created when a connection is made to the water supply system, the
central heating system, metal walls etc. The loop is closed by means of the equipotential
bonding strip.
If possible, care should be taken as early as the planning stage to prevent the creation of
loops. Bus and mains cables should be installed as close to each other as possible. An
appropriate distance should be observed from the water supply or central heating system,
etc. If line-crossing loops occur in a KNX TP installation, it may under certain circumstances
not be possible to properly program the installation.
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15 Basic immunity of bus devices
The basic immunity of bus devices is tested according to the standard EN 50491-3 by
applying a 2 kV surge voltage core to earth. As a consequence, bus devices are protected
against overvoltages often caused by switching operations.
In general this provides sufficient protection. More significant interference can however be
caused:
 when bus cables and high-power mains are installed in parallel over a longer distance,
 in the vicinity of lightning rods and arresters,
 when bus lines and conductive parts of an installation (through which lightning current
can flow) are installed in parallel,
 in loops,
 in bus devices connected to conductive sections such as metal walls, central heating
pipes etc.
16 Bus devices on cable ends
In this case, additional secondary protection should be provided.
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17 The overvoltage arrester terminal
Bus overvoltage arrester
Recommended usage
 To bus devices with 230 V mains connection
 To line and area couplers on both lines
 To bus devices installed in conductive walls or in
the vicinity of water pipes, gas pipes etc.
 To bus cable ends
 At the edge of buildings
Figure 17: The overvoltage arrester terminal
The overvoltage arrester terminal should be used as a secondary protection and shall meet
the following requirements:
 nominal discharge current at least 5 kA (8/20 µs)
 protection level: < 350 V
 KNX certified
The overvoltage arrester terminal is a symmetrical safety device discharging both bus wires,
thus preventing large voltage differences. Single pole arresters should not be used. Due to
their higher capacity, varistors are also not suitable for this purpose.
Via the connection wires sticking out of the bus overvoltage arrester (which have an
identical colour marking as the bus cable, i.e. red and black), the arrester can be connected
by means of a conventional bus connector to the bus cable or directly to a bus device.
However, the bus overvoltage arrester cannot be used to branch the bus cable. The third
green connection wire is the earthing conductor, which should be connected to the nearest
earthing point of the installation (i.e. protective earth conductor).
In the case of flush-mounted bus devices and couplers, the overvoltage arrester terminal is
directly connected to the bus device instead of using a bus connector.
In this case, the connection between wires is ensured by means of an externally mounted
bus connector.
The arrester terminal also replaces the bus connection block when couplers are to be
connected in the main line.
In the case of DIN rail mounted bus devices in general, e.g. power supply units and
secondary lines of couplers, the overvoltage arrester terminal should be connected to a data
rail connector, if the devices are fed via a data rail.
The earthing conductor of the distribution board must be connected to the protective earth
conductor (PE) by means of a non-earthed DIN rail terminal.
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18 Recommendations to the use of overvoltage arresters
The use of overvoltage arresters is recommended for:
 bus devices with protection class 1
 bus devices with more connections than just bus (230/400 V AC and/or pipes of the
heating system)
In distribution boards, it is sufficient to equip each bus line with one overvoltage arrester. In
this case also the outer conductor and the neutral conductor need to be equipped with
overvoltage arresters.
For luminaries with built-in switching actuators the installation of overvoltage arresters is
only necessary when the bus and the mains form large-surface loops.
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19 Checking the installation
Checking an installation
1. Check whether permitted cable lengths have been observed
2. Run a visual check of the marking of the bus cable ends
3. Check installation for inadmissible cable connections
4. Measure the insulation resistance of the bus cables
5. Check polarity of all bus devices
6. Measure voltage at each bus cable end (minimum 21 V)
7. Record your test results
Figure 18: Checking the installation
1. Voltage drops and increase of the transmission duration of telegrams are the result of
ohmic resistance, capacity and inductance of bus cables. This again causes the physical
limits of a KNX TP installation as outlined below.
Length of a line segment
max. 1000 m
Distance between power supply unit - bus device
max. 350 m
Distance between two power supply units, including
chokes
As specified by the
manufacturer
Distance between two bus devices
max. 700 m
It may be helpful to measure the loop resistance of the bus line under test.
2. The ends of the bus cables should be clearly identified as KNX TP by marking them KNX
TP or BUS. An extra indication of the area and line will make it easier to locate a specific
bus cable for testing, commissioning or maintenance purposes.
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3. Bus cables from different lines may never be connected together. Inadmissible
connections between the individual lines can be checked by switching off the power
supply unit of the line under test. If the power LED of the line coupler continues to light,
an inadmissible connection has been detected.
4. The measurement of the insulation resistance of the bus cable should be carried out at
250 V DC. The insulation resistance shall be at least 500 k. The measurement is carried
out as conductor against PE and not conductor against conductor.
Please note: Overvoltage arrester terminals should always be removed before carrying
out the test, so that the measurement is not influenced and the overvoltage arrester is
not damaged.
5. A polarity check should be carried out on all bus devices. To do so, set the bus device
into programming mode by pressing the programming button. If the programming LED
lights up, the bus device is correctly connected. To finish the check, press the
programming button again. This switches the bus device back to normal operating mode
and resets the programming LED.
6. After having mounted all bus devices, check the bus voltage at the end of each bus cable
using a voltmeter. The voltage should be at least 21 V DC.
7. Record all test results and add them to the documents of the KNX TP installation.
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20 Information to the use of data rails
Data rails, data rail covers in certain installations
Self adhesive data rail for 35 mm DIN rail
The data rail is offered in various standardized
lengths:
KNX Data rail 243 mm
Make sure that:



Data rail cover

Keep the data rail clean
Do not cut the data rail
Do not solder the data rail
Cover unused sections
Figure 19: Data rail, data rail covers
In some installations data rails are required to connect DIN rail type bus devices, such as
binary outputs, dimmers, power supply unit etc.to KNX TP.
The self-adhesive data rail is mounted on the 35 mm DIN rail according to EN 50022.
The lengths of the data rails match the various widths of the standardised electric power
distribution boards. These lengths may not be changed afterwards, for instance by cutting it
shorter, as this would change the creepage and clearance distances.
When DIN rail mounted KNX TP bus devices use the data rail to connect to the TP bus when
snapped on the DIN rail, they do so by means of a pressure contact mechanism.
In order to protect unused sections of data rail from pollution or from accidental contact
with mains cables, they should be covered by a data rail cover.
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21 Power supply unit with data rail
DVC
>= 21 V DC
Connection with
screwless terminals
TP Connectors
DVC
>= 21 V DC
Bus line
Spring contacts
PS +
Bus +
Bus PS -
Power supply unit
Choke
Connector
230 V
50/60 Hz
DIN Rail with data rail
30 V DC 640 mA
> 100 ms buffer
Figure 20: Power supply unit (on DIN rail with data rail)
The above figure shows the bus connection of the power supply unit connected via spring
contact blocks to the printed conductors of the data rail. This type of connection i.e. the
standard data rail glued into the DIN rail can be found in old installations. The bus cable is
connected to flush mounted bus devices via a 2-pole data rail connector.
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22 Power supply unit for two lines with data rail
Connection with
screwless terminals
DVC
>= 21 V DC
230 V
50/60 Hz
Line 1
Power supply unit
DIN Rail with data rail
Connector
2-pole
PS +
Bus +
Bus PS -
Choke
30 V DC 640 mA
> 100 ms buffer
Spring contacts
PS +
Bus +
Bus PS -
Line 2
DVC
>= 21 V DC
Connector 4-pole
30 V DC Ancillary voltage
White
Yellow
Choke
Bus voltage
Figure 21: Power supply unit for two lines (on DIN rail with data rail)
A power supply unit of e.g. 30 V DC and 640 mA with pins connecting to data rail can be
used for feeding two lines.
By means of the integrated choke, the 30 V DC voltage is fed to the DIN rail devices via pins
and the two inner printed conductors of the data rail.
The connection to the TP bus cable is realized via a data rail connector (2-pole or 4-pole
connectors are available).
Via the ancillary voltage output (white/yellow) it is possible to feed the ancillary voltage to
the outer printed conductors of the data rail by means of a 4-pole data rail connector.
A separate choke then feeds the ancillary voltage via the inner printed conductors of the
data rail as 30 V DC bus voltage to the DIN rail devices. It is also possible here to connect the
bus cable by means of a 2-pole or 4-pole data rail connector.
The 2-pole data rail connectors have screwless terminals and the 4-pole data rail connectors
are connected to the TP bus cable by means of the standardized bus connectors.
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Mutxamel (Alicante)
T: +34 965959511
E: info@futurasmus-knxgroup.com
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