EN 61175:2005

SLOVENSKI SIST EN 61175:2006
STANDARD
marec 2006
Industrijski sistemi, inštalacije, oprema in industrijski proizvodi – Oznake
signalov (IEC 61175:2005)
Industrial systems, installations and equipment and industrial products –
Designation of signals (IEC 61175:2005)
ICS 29.020 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 61175
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2005

ICS 29.020 Supersedes EN 61175:1993

English version
Industrial systems, installations
and equipment and industrial products -
Designation of signals
(IEC 61175:2005)
Systèmes, installations, appareils  Industrielle Systeme, Anlagen und
et produits industriels - Ausrüstungen und Industrieprodukte -
Désignation des signaux Kennzeichnung von Signalen
(CEI 61175:2005) (IEC 61175:2005)

This European Standard was approved by CENELEC on 2005-11-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61175:2005 E
Foreword
The text of document 3/753/FDIS, future edition 2 of IEC 61175, prepared by IEC TC 3, Information
structures, documentation and graphical symbols, was submitted to the IEC-CENELEC parallel vote
and was approved by CENELEC as EN 61175 on 2005-11-01.
This European Standard supersedes EN 61175:1993.
It includes the following significant technical changes with respect to EN 61175:1993:
The structure of the signal designation has been extended and specified in more detail:
– the term “item designation” has been replaced by “reference designation” with the same meaning
as before;
– the term “basic signal name” has been extended. It has been replaced by “signal name”; then
subsequently consisting of “class”, “short name” and “basic signal name”, where “basic signal
name” has the same meaning as before;
– classification codes have been introduced in order to facilitate the understanding of the signal
name, for example the type of signal and hence the “signal direction” can be recognized by the
code;
– the concept of “signal name domain” has been introduced for improved identification of signal
name in relation to an applicable object;
– the term “version identifier” has been changed to “variant” with the same meaning as before;
– the earlier possibility to provide additional information on “signal level” has been generalized to an
area of “additional information” to be used to supplement information on “version”, “time stamp”,
“level” and other system related parameters. The additional information is stated to belong to a
variant of the signal (not to the signal designation in general).
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-11-01
Annex ZA has been added by CENELEC.
__________
- 3 - EN 61175:2005
Endorsement notice
The text of the International Standard IEC 61175:2005 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60227 NOTE The HD 21 series is related to, but not directly equivalent with the
IEC 60227 series.
IEC 61355 NOTE Harmonized as EN 61355:1997 (not modified).
IEC 61850-4 NOTE Harmonized as EN 61850-4:2002 (not modified).
__________
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
NOTE NOTEWhere an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60417 data- Graphical symbols for use on equipment - -
base
1) 2)
IEC 60445 - Basic and safety principles for man- EN 60445 2000
machine interface, marking and
identification - Identification of equipment
terminals and of terminations of certain
designated conductors, including general
rules for an alphanumeric system

1) 2)
IEC 60447 - Basic and safety principles for man- EN 60447 2004
machine interface, marking and
identification - Actuating principles

3) 3)
IEC 61082-1 - Preparation of documents used in EN 61082-1 -
electrotechnology
Part 1: Rules
IEC 61131 Series Programmable controllers EN 61131 Series

IEC 61346 Series Industrial systems, installations and EN 61346 Series
equipment and industrial products -
Structuring principles and reference
designations
ISO/IEC 646 1991 Information technology - ISO 7-bit coded - -
character set for information interchange

ISO/IEC 8859-1 1998 Information technology - 8-bit single-byte - -
coded graphic character sets
Part 1: Latin alphabet No.1
1)
Undated reference.
2)
Valid edition at date issue.
3)
To be published.
NORME CEI
INTERNATIONALE
IEC
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2005-09
Systèmes, installations, appareils
et produits industriels –
Désignation des signaux
Industrial systems, installations and
equipment and industrial products –
Designation of signals
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For price, see current catalogue

61175  IEC:2005 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11

1 Scope.13
2 Normative references .13
3 Terms and definitions .15
4 Basic rules .17
4.1 Structure of the signal designation .17
4.2 Recommended characters .23
5 Signal classification.25
5.1 General .25
5.2 Signal classes .25
5.3 Reporting signal kind.25
5.4 Controlling signal kind .33
6 Rules for the identification of the signal transfer .37
6.1 General .37
6.2 Variants.37
6.3 Binary logic representation .41
6.4 Numerical data communication and software programming.45
7 Signal presentation.45
7.1 Human System Interface, HSI .45
7.2 Documentation .47
8 Application .47
8.1 Presentation of signals in signal property lists .47
9 Conformance classes .53
9.1 Conformance class 1.53
9.2 Conformance class 2.55

Annex A (informative) Letter codes and mnemonics for use in signal names.57
A.1 Letter codes for variables .57
A.2 Special letter codes for electrical variables.57
A.3 Letter codes used as modifiers .59
A.4 Identification of terminations of certain designated conductors .59
A.5 Mnemonics for use in the basic signal name.61

Annex B (informative) The signal concept .75
B.1 Description and clarification of the signal concept .75
B.2 Signal information model .75
B.3 Signal transfer (connection).85

Bibliography.91

61175  IEC:2005 – 5 –
Figure 1 – Signal naming structure .19
Figure 2 – Examples of typical reporting signals .27
Figure 3 – Example of an indication signal .27
Figure 4 – Example of an event signal .29
Figure 5 – Example of measuring signals.29
Figure 6 – Example of an analogue signal.31
Figure 7 – Example of additional information .31
Figure 8 – Example of parts of an analogue signal.33
Figure 9 – Example of constant level signals .33
Figure 10 – Examples of typical controlling signals .35
Figure 11 – Example of a command signal.37
Figure 12 – Example of a signal for setting value .37
Figure 13 – Signal variants in a signal connection chain .39
Figure 14 – Signal variants using manufacturer defined signal names.41
Figure 15 – Signal states of binary signals.43
Figure 16 – Example of a negated signal .45
Figure 17 – Signal property presentation list and a corresponding XML file.47
Figure 18 – Voltage measurement, reporting signal class ( M ) .51
Figure 19 – Command signal for a disconnector, controlling signal class ( C ) .53
Figure 20 – Example of signal designation corresponding to conformance class 1 .55
Figure 21 – Example of signal designation corresponding to conformance class 2 .55
Figure B.1 – Reporting signal.77
Figure B.2 – Controlling signal.79
Figure B.3 – Use of signal designations within objects .81
Figure B.4 – Example of signal designation with “time stamp”.83
Figure B.5 – A typical signal connection chain .85
Figure B.7 – The static representation of the signal transfer .87
Figure B.8 – The dynamic appearance of the signal transfer .87

Table 1 – Letter codes for signal classes .25
Table A.1 - Letter codes for variables .57
Table A.2 – Special letter codes for electrical variables .59
Table A.3 – Letter codes used as modifiers .59
Table A.4 – Identification of certain designated conductors.59
Table A.5 – Mnemonics for use in descriptive signal messages .61

61175  IEC:2005 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL SYSTEMS, INSTALLATIONS AND
EQUIPMENT AND INDUSTRIAL PRODUCTS –
DESIGNATION OF SIGNALS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61175 has been prepared by IEC technical committee 3:
Information structures, documentation and graphical symbols.
This second edition cancels and replaces the first edition published in 1993. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition.
The structure of the signal designation has been extended and specified in more detail:
– the term “item designation” has been replaced by “reference designation” with the same
meaning as before;
– the term “basic signal name” has been extended. It has been replaced by “signal name”;
then subsequently consisting of “class”, “short name” and “basic signal name”, where
“basic signal name” has the same meaning as before;

61175  IEC:2005 – 9 –
– classification codes have been introduced in order to facilitate the understanding of the
signal name, for example the type of signal and hence the “signal direction” can be
recognized by the code;
– the concept of “signal name domain” has been introduced for improved identification of
signal name in relation to an applicable object;
– the term “version identifier” has been changed to “variant” with the same meaning as
before;
– the earlier possibility to provide additional information on “signal level” has been
generalized to an area of “additional information” to be used to supplement information on
“version”, “time stamp”, “level” and other system related parameters. The additional
information is stated to belong to a variant of the signal (not to the signal designation in
general).
The text of this standard is based on the following documents:
FDIS Report on voting
3/753/FDIS 3/779/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
61175  IEC:2005 – 11 –
INTRODUCTION
The intention of this International Standard is to make rules and requirements for the
designation of signals, and furthermore to make recommendations on useful presentations of
these.
Basically, a signal designation is associated to the signal over its whole lifetime, which
means: from the beginning of the design stage until the signal is no more needed.
Designation of a signal, in accordance with this standard, means that the source and the
destination of the signal are identified, also in intermediate interfaces where the signal is
delivered from one system/media to another, but the identification itself is independent of the
media used for transfer of the signal.
To comply with rules and procedures for different systems and media transferring signals, it is
described in this standard how to handle special information in a system and/or in between
systems as “additional information” if needed.
The change of medium for the transfer of a signal because of a physical rebuilding of an
installation will not cause a change of the identification of this signal if its meaning is
maintained. The kind of physical transportation of a signal has no influence on the
identification of it, unless this physical transportation is a part of the signal purpose.
Rebuilding of installations might lead to wishes to transfer more signals in the same physical
medium. All of such additional signals will be identified in accordance with their purpose and
the rules stated in this standard.
As the identification of a signal has nothing to do with the physical transportation of it, the
lines in the figures in this standard will be read as “signals” more than “connections”.

61175  IEC:2005 – 13 –
INDUSTRIAL SYSTEMS, INSTALLATIONS AND
EQUIPMENT AND INDUSTRIAL PRODUCTS –
DESIGNATION OF SIGNALS
1 Scope
This International Standard provides rules for the composition of designations and names for
the identification of signals and signal connections. This includes the designation of power
supply circuits.
The standard is applicable to all types of signals within an industrial system, installation and
equipment.
The standard is not applicable for the identification of wiring, terminals and other hardware for
connections.
The standard does not establish rules for
• the graphical/physical representation of a signal on devices, nor
• the graphical representation of signals in documentation.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60417, Graphical symbols for use on equipment
IEC 60445, Basic and safety principles for man-machine interface, marking and identification
– Identification of equipment terminals and of terminations of certain designated conductors,
including general rules for an alphanumeric system
IEC 60447, Basic and safety principles for man-machine interface, marking and identification
– Actuating principles
IEC 60747, Semiconductor devices - Discrete devices
IEC 61082-1 , Preparation of documents used in electrotechnology – Part 1: Rules
IEC 61131 (all parts), Programmable controllers
IEC 61346 (all parts), Industrial systems, installations and equipment and industrial products
Structuring principles and reference designations
ISO/IEC 646: 1991, Information technology ISO 7-bit coded character set for information
processing interchange
ISO/IEC 8859-1: 1998, Information technology – 8-bit single-byte coded graphic character
sets – Part 1: Latin alphabet No. 1
———————
To be published.
61175  IEC:2005 – 15 –
3 Terms and definitions
For the purposes of this document, the following definitions apply.
3.1
signal
unit of information conveyed from one object to another
NOTE Messages (units of signals) may be sent in a communication network in the form of telegrams. Such
messages may represent one or several signals.
3.2
signal designation
unambiguous identifier of a signal within a system
3.3
signal connection
path on which the signal is transferred between the interface points
NOTE The connection can be identified as logical or physical, and can be realized in different connection media.
A complete signal connection chain may include different media.
3.4
signal connection chain
group of coherent signal connections belonging to the same signal
NOTE The signal connection chain will typically describe the complete connection of the signal transfer.
3.5
signal connection medium
medium in which the signal is transferred from one point to an other
NOTE The medium can be identified as logical or physical, and a complete signal connection chain may include
different media.
Examples:
- Physical media: electric wire, optic fibre.
- Logical media: single data transfer, communication bus or network.
3.6
signal name domain
chosen object in which each signal name is unambiguous without using the reference
designation
3.7
signal presentation
way of presentation of a reporting signal
NOTE 1 Example: digital display, analogue indication, lamp, semaphore.
NOTE 2 The complete signal designation does not have to be used in the presentation (but it can be). It is
recommended that the complete signal designation should be possible to find from the signal presentation.
3.8
signal kind
super-type of the signal class defining direction of information in the signal connection
NOTE Two signal kinds are used:
- reporting signals; and
- controlling signals.
61175  IEC:2005 – 17 –
3.9
signal class
groups of signals defined in accordance with a classification scheme based on the purpose of
the signals
NOTE The signal class is indicated by a code in the signal designation.
3.10
signal variant
identified section of the signal connection chain
NOTE There is always at least one variant in a signal connection chain.
3.11
object
entity treated in the process of design, engineering, realization, operation, maintenance and
demolition
[IEC 61346-1:1996, definition 3.1]
3.12
object designation
identifier of a specific object
[IEC 61355:1997, definition 3.12]
3.13
reference designation
identifier of a specific object with respect to the system of which the object is a constituent,
based on one or more aspects of that system
[IEC 61346-1:1996, definition 3.7]
3.14
data point
physical point in the signal connection chain, where a message can be inspected and the
current value of a signal can be accessed
3.15
data object
signal group composed of one or more data items (signals)
NOTE A data object is used to represent the specific elements of functionality of a device.
3.16
version
identification of a specific edition/version of the information
NOTE Example:
- Version 1 is the message for time 0; and
- Version 2 is the message for time 0 + 1 s.
4 Basic rules
4.1 Structure of the signal designation
A signal designation shall unambiguously identify a signal among a set of points (terminal,
junction, data point) within a system (see IEC 61346-1) and may also classify the signal.

61175  IEC:2005 – 19 –
The structure of a signal designation shall be based on standardized and system related parts
and their sub-parts for identification and classification, following each other in an organized
and specified way. All parts may be represented for different purposes textually for human
presentation or by codes for other purposes according to a documented principle.
OBJECT SIGNAL
OBOBJECJECTT ; ;
SISIGNAGNALL
OBJET SIGNAL
RReeffeerrencence dese desiignatgnatioion n ofof the the objecobjectt
wiwithithinn wh whiicch thh the e ssiignalgnal nnaammee i iss
ununamambibiguousguous ( (ssiiggnalnal nam name dome domainain)).
DDeesisiggnnaattioionn a anndd cl claassissiffiicacattiioonn ooff
ssiignalgnal wi witthhin in ththe obe objecjectt
IIddententiiffiierer f foorr sseeccttioion ofn of t thhe e ssiignalgnal
ccoonnecnnecttiion con chhaiainn
CCllasasssiiffiiccaatition on and dand deessccrriippttiion ofon of
ththee v vaarriiaanntt:: V Veerrssiioonn,, ti timmee ssttaammpp,,
systsysteemm in inffoo,, li limimittss ((lleevveell),), vavalluuee
anand und unitit
SiSignalgnal desi designatignationon ::  REFREF DESI DESIGN GN ;; SIGSIGNNAALL NAMNAME E : V: VAARIRIAANNT (T (ADDIADDITTIIOONAL INAL INNFORFORMMATIOATION)N)
SiSignalgnal name name ::  CCLLAASSS_S_SHSHOORRTT NA NAMMEE__BBAASSICIC SSIIGNAGNALL NNAAMEME
CCllaassssiiffiiccaattiion con code:ode:
ffoorr Repo Reporrttiing Sng Siigngnalsals s see ee ttaable Bble B1 .11
ffoorr Cont Contrroolllliing Sng Siiggnalsnals ssee ee ttablablee B B.22
SShorhort t exextetensnsionion t too t the he objecobjectt de deffiinniingng
tthhee re rellaatteedd ppaarrtt o off t thhee systsysteemm
MMnemnemononicicss ac accc. ttoo ttable Aable A.55
DDeessccrriptiptiionon ofof tthe she siigngnal mal meessssage usage use e
mmnemnemononicicss ac accc. ttoo ttable Aable A.5 5 oorr c conconcerernniing ng
mmaarrkkiing ofng of c conduconducttoorrss acaccc. t too ttable Aable A.4 4
oror i iff ccoded:oded:
11sst lt leetttteerr acaccc. t too  ttable Aable A.1 or1 or A A.22
IEC  1619/05
2nd2nd l leetttterer acaccc. t too ttable Aable A.3 or3 or A A.44

Figure 1 – Signal naming structure
The structure of the signal designation shall be:
REF. DES. ; SIGNAL NAME : VARIANT (ADDITIONAL INFORMATION)
See Figure 1, where:
REF. DES. is the designation of the object (the signal name domain) inside which
the signal name is unambiguous and valid (see 4.1.1);
; is the prefix of SIGNAL NAME;
SIGNAL NAME is the unambiguous designator of a signal, valid inside a specified
object (the signal name domain) (see 4.1.2);
: is the separator between SIGNAL NAME and VARIANT or ADDITIONAL
INFORMATION if a variant is not used;

61175  IEC:2005 – 21 –
VARIANT is the designation of the variant of the signal (see 4.1.3);
( ) indicates a additional information;
ADDITIONAL INFORMATION
is the description and possible subclass of the variant of the signal (see
4.1.4).
4.1.1 Reference designation
The signal name domain shall be represented by a reference designation. This shall
preferably be in accordance with IEC 61346-1 (see also descriptions in Annex B). This
reference designation shall not be part of the signal name used inside the signal name
domain.
4.1.2 Signal name
The signal name shall designate, and may classify and describe the signal generally. The
signal name shall include a basic signal name and may include a short name and a class as
described below. The signal name shall be preceded by the prefix (;) The prefix shall be
presented in documents. The prefix may be omitted in a document in which signal names are
undoubtedly identified as such, for example in a signal list.
The structure of the signal name shall be:
CLASS _ SHORT NAME _ BASIC SIGNAL NAME
where
CLASS is the code of the signal class (see Clause 5);
NOTE Subclasses are to be placed (found) in ADDITIONAL INFORMATION
SHORT NAME is a short textual description of the reporting object respectively the
controlled object;
BASIC SIGNAL NAME is the short description of the signal defining the special function of
the signal (see Annex A for abbreviations recommended to be used
in BASIC SIGNAL NAME).
NOTE For enhanced readability, it is recommended to use the underscore sign for separation between the sub-
parts of the signal name.
4.1.3 Variant
The variant part of the signal designation shall be used to identify a section of the signal on
the way from the source to the destination where necessary. If there is only one section, it is
not required to use variant numbers or codes, but the separator in front of the variant part
shall be used if additional information is added to the signal name. See also the description of
variants in 6.2 and Clause B.3.

61175  IEC:2005 – 23 –
Examples of cases where the separation in different variants is applicable are:
• from one functional representation to another;
• from one electrical net to another;
• from one component to another;
• from one signal connection medium to another.
4.1.4 Additional information
The additional information of the signal designation shall describe the characteristics of the
signal variant. See also Figure 7 and B.2.1.3.
NOTE The additional information part should be used only where necessary.
The additional information of a signal variant, if used, may include data for
• version, time stamp or level, etc.;
• system information, for example protocol related parameters; and also
• other system information.
Version number or time stamp in the additional information may be used to create an
unambiguous identifier of a specific version.
4.2 Recommended characters
Signal designations should be composed from standard character sets.
Different mnemonics, abbreviations, identifiers, suffixes, etc. within a name may be separated
by a single space or by an underscore (_) to enhance readability. To maintain compatibility
with computer processing, character sets should be restricted to those characters in the
ISO/IEC 646 7-bit character set, basic code table, excluding control characters and national
replacement characters.
If the computer and communication systems that are to be used are restricted to those that
can process 8-bit character sets, ISO 8859-1 is recommended for supplementary characters.
The recommended characters include the following:
• capital letters A through Z;
• lower case letters a through z;
• digits 0 through 9;
• negation: see 6.3.2;
• spacing characters: underscore (_) or space;
• name prefix: semicolon (;);
• variant separator: colon (:);
• indicator of additional information: ( );
• Boolean operators: raised dot (.);
• special characters: ! ‘‘ % & ‘ *, . / < = > – + ?

61175  IEC:2005 – 25 –
5 Signal classification
5.1 General
It is recommended to use signal classification based on the kind and the purpose of the
signal.
5.2 Signal classes
If used, the signal class shall be represented by a letter code in the signal name (see 4.1.2).
The code shall be selected in accordance with this clause.
NOTE The use of the classification code was not a part of the first edition of this standard.
Two major kinds of signals can be recognized, reporting signals and controlling signals;
the two kinds being characterized based on the direction of the signal information between
controlling and controlled object.
The following letter codes shall be used as introduction to the signal name to identify the
signal class.
Table 1 – Letter codes for signal classes
Code Class Kind Reference
A Alarm signal Reporting signal See 5.3.2
C Command Controlling signal See 5.4.1
E Event signal Reporting signal See 5.3.2
I Indication signal Reporting signal See 5.3.1
L Constant level signal Reporting signal See 5.3.4
M Measuring signals Reporting signal See 5.3.3
S Setting value Controlling signal See 5.4.2
X(n) Additional class Reporting signal
Y(n) Additional class Controlling signal
NOTE “Additional class” is specified and documented for a specific application, and numbers are used if more
then one additional class is requied.
The classification, including additional class, shall not be related to the appearance of a
specific variant of the signal, but to the signal itself. If a signal representation in a variant of
the signal should be classified, it may be identified by a code (subclass) in “Additional
Information” (see 4.1).
5.3 Reporting signal kind
A reporting signal shall transfer information from the reporting object (source) to one or more
destinations (receivers of the message). The reference designation of the signal name domain
in which the reporting object is situated shall be used to identify a reporting signal.
The destination of a reporting signal will often be a human person but can also be a
mechanical or computerized system, etc.
Figure 2 shows examples of
a) different reporting signals from one soure to several destinations, and
b) several variants of the same reporting signal to two destinations.

61175  IEC:2005 – 27 –
RReeff. d deessiigngn ; ; Si Signgnaall nanammee 1 1
DeDessttininatatiioonn 1 1
ReReportingporting oobbjjeectct

RReeff. d deessiigngn ; ; Si Signgnaall nanammee 2 2
a)a)
SensSensoror DDeessttiinnaattion 2ion 2
a)
RReeff. de dessiigngn ;; Si Signgnal naal nammee 3 3
DDeessttiinnaattion 3ion 3
EExxaammplple ofe of SSiiggnalnal N Naammee o off::
EvEventent s siiggnalnal ;;EE_P_Pumumpp__SSttartart
IInndidiccaattiioonn s siignagnall ;;II__EE--SSww_Ope_Openn
ConsConsttaanntt l leevveel sl siiggnalnal ;;LL__DDCC55_M11_M110+0+
MeasMeasurinuringg s siiggnalnal ;;MM_CT_CT2_I2_I1L1L33
ClClasasssiiffiiccaattiionon c codeode
ShShorortt n naammee
BBaassiicc s siignagnal nal nammee
DeDeststinainattioionn 1 1
==MMAA11;;EE__MMotot_S_Sttaarrtt:: 2 2
=M=MA1A1
PanelPanel
RReepoporrttiningg ob objjeectct

;E;E__MMoott__SStatarrt: 1t: 1
b)b)
MoMotortor
b)
DestiDestinationation 2n 2
==MMAA11;;EE__MMotot_S_Sttartart : : 33
DeDesskk
SiSigngnaall na nammee dom domaaiinn

IEC  1620/05
Figure 2 – Examples of typical reporting signals
5.3.1 Indication signal ( I )
An indication signal is a reporting signal that has two states, active or not active. The basic
signal name shall be related to the active state. If information about two positions is needed,
two signals have to be defined.
NOTE The two states may be indicated by one device and transmitted by one electric conductor where energised
conductor means one position and non-energised means the opposite position. However, this method of
transferring indication signals is not recommended because the non-energised conductor will both indicate a
position and loss of connection.

RefRef. Desig Designn. ;;II_E_E-S-Sww__OOppenen
RefRef. Desig Designn. ;I;I__EE--SSww__CClloossee
RefRef. Des Desiign.gn. ;;LL_D_DC_110C_110VV

IEC  1621/05
Figure 3 – Example of an indication signal

61175  IEC:2005 – 29 –
5.3.2 Alarm and event signals ( A and E )
Alarm and event signals are reporting signals with two states as indication signals, but used
to notify the receiver about a specific event when it happens or, via attached data, what has
happened and/or when it happened.
NOTE Typically, these types of signals are created by the signal source in the case of changed status, for
example a in process supervisory device.
An alarm signal shall be used to indicate an event of an abnormal situation in a supervised
system and shall be specified (by the receiver) for specific treatment (alarm purposes) in the
receiving system.
The event of other situations shall be indicated by event signals.
Event list
EEvvenent Lit Lisstt
RefRef. Desig Designn. ;;EE_Pu_Pummpp__SSttarartt
PuPummpp No No. 1. 1
##
IIndicndicaattiionon,, St Startart

IEC  1622/05
Figure 4 – Example of an event signal
The difference between the classes indication signal, alarm signal and event signal is not
obvious from the position of the signal source. The class ( I ) should be used in cases where
the purpose of the signal is not completely clear.
5.3.3 Measuring signal ( M )
A measuring signal is a reporting signal used to represent a value considered to be
continuously variable. The physical signal itself can be analogue or consist of a number of
levels and/or time dependent discrete indications.
If the basic signal name needs to be coded, letter codes according to Table A.1 or A.2 should
be used as the first character, and letter codes according to Table A.3 should be used as
second character (for examples, see Figure 5).
;;MM_C_CTT2_I2_I11LL33
;M_C;M_CTT2_I1L32_I1L3
wwherheree::
;;MM_C_CTT2_I2_I11LL22
MM i iss MMeasurineasuring sig signal gnal
;;MM_C_CTT2_I2_I11LL11
CCTT2 i2 iss sh shorort nt naamme e ffoorr
currentcurrent t trransfansfoorrmmer 2er 2
I iI iss C Cuurrrrentent ;;MM_C_CTT2_I2_I11NNEE
1 is Core 11 is Core 1
L3 is PL3 is Phasehase L3L3
IEC  1623/05
Figure 5 – Example of measuring signals

61175  IEC:2005 – 31 –
Analogue signals have a continuous range of possible physical values; the name for such
signals should describe “the variable or function” represented by the signal.
The basic signal name for an analogue signal can be plain language or coded (see Annex A).

TrTranansdsduucercer
RReeff. Desig Designn.;M_V;M_VT1_ULT1_UL11++ ;;MM_V_VT1_ULT1_UL11
Ref.Ref. Desi Desiggnn.;.;MM__VVTT1_U1_ULL11-- ;;MM__VVT1_UNET1_UNE
~~
Analogue d.c. signal
Analogue a.c. signal
AAnnaallogueogue D DCC s siignagnall AnAnaalloogguuee AC AC ssiiggnnaall

Figure 6 – Example of an analogue signal
IEC  1624/05
The measuring device that generates the measuring signal, the transportation medium and
the presentation, may represent the signal in different forms (see examples in Figure 7).
However, since the information is in all cases the same and therefore the same signal name
shall be used, the different forms shall be defined as variants of the signal.
The identification of the signal variant may include additional information about the form of
representation. Specific attributes related to the form, for example time stamps of digital
messages of analogue values may be added to the variant.

CoCoCommmmmmuuunininicacacatttiiion meon meon messa
...