oSIST prEN IEC 60073:2026

• Status: Not Published
• Public Enquiry End Date: 30-Oct-2026
• ICS: 01.070 - Colour coding
• ICS: 13.110 - Safety of machinery
• ICS: 29.020 - Electrical engineering in general
• Technical Committee: EDO - Documentation and graphical symbols
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 18-Aug-2026
• Due Date: 05-Jan-2027
• Ref Project: prEN IEC 60073:2026 - Basic and safety principles for man-machine interface, marking and identification - Coding principles for indicators and actuators

• Revises: SIST EN 60073:2003 - Basic and safety principles for man-machine interface, marking and identification - Coding principles for indicators and actuators
• Effective Date: 11-Jun-2024

oSIST prEN IEC 60073:2026 is the Slovene adoption of IEC prEN IEC 60073:2026, published by SIST. It sets coding principles for indicators and human-machine interface (HMI) actuators by using visual, acoustic and tactile signals to support safe monitoring, control and maintenance of equipment and processes.

The standard is for engineers, safety specialists and technical committees that need a common HMI signalling language. It tells users how to assign meanings to colours, shapes, sounds and tactile cues so that controls and indicators are easier to recognise and less likely to be confused.

What does oSIST prEN IEC 60073:2026 specify?

oSIST prEN IEC 60073:2026 establishes general rules for assigning meanings to certain visual, acoustic and tactile indications. Clause 1 says the aim is to improve safety, support proper monitoring and maintenance, and help operators recognise control conditions and HMI actuator positions quickly.

The standard applies from simple devices such as indicator lights, push-buttons, mechanical indicators, light emitting diodes (LEDs) and video display screens up to larger control stations. It is also intended for cases where a technical committee assigns a specific coding scheme to a special function.

The document is organised into clauses 1 to 5, with three annexes and a bibliography. Annex A is normative and Annexes B and C are informative.

Annex	What it covers
Annex A	Special requirements for mechanical indicators
Annex B	Example of indication coding using colours
Annex C	Examples of visual, acoustic and tactile signals

The standard is also identified as a Basic safety publication, so it is meant to be used as a foundation when preparing safety-related publications.

What are the key requirements of oSIST prEN IEC 60073:2026?

Choosing a coding method

Clause 4.1 says coding principles should be decided early in system design and kept consistent across the same plant or process. The selected code must fit the task, the operating conditions and the information that needs to be communicated, and its meaning must be explained in the equipment or plant documentation.

Clause 4.1 also allows more than one coding method at the same time. Table 2 lists the characteristics to consider for visual, acoustic and tactile codes, such as hue, brightness, position, sound type, vibration and surface roughness. In practice, this means a single cue should not be chosen just because it is available - it has to work in the real operating environment.

Visual signals and colour coding

Clause 4.2.1 says colour and flashing are the most effective visual means for attracting attention, but colour must not be the sole means of coding. Where safety of persons or the environment is involved, supplementary coding shall be provided, and if colour cannot be used, the standard turns to shapes, position or other indication methods.

Clause 4.2.2 assigns meanings to RED, YELLOW, GREEN, BLUE, WHITE, GREY and BLACK. Red is linked to danger, emergency and faulty conditions; yellow to warning or abnormal conditions; green to safe or normal conditions; and blue to mandatory significance. Other colours may be used, but their meanings are not defined here, so users should not rely on them for a shared meaning unless they define that meaning themselves.

Clause 4.2.2 and 4.2.3 also require adequate contrast, consistent use and clear distinction from the background and from other assigned colours. Shapes may be used as the main code or as a backup to colour, which is important where colour vision is limited or lighting conditions are poor.

Clause 4.2.4 uses changing characteristics over time, especially flashing, to request immediate action, show a mismatch, or show a transition. The faster flashing frequency carries the higher-priority meaning, so the flashing pattern becomes part of the message and has to be controlled consistently.

Acoustic and tactile signals

Clause 4.3 limits acoustic signals to cases where attention, rapid response or redundancy is needed. Acoustic signals must be audible and clearly distinguishable in the intended reception area, and they must not be confused with the emergency evacuation signal. The clause also keeps the number of different sounds low to avoid overloading operators.

Clause 4.4 allows tactile signals only in restricted cases and only where there is direct and continuous contact with the body. They are not to be the only source of information and are intended for skilled or instructed persons. In practice, this means vibration or force can support other signals, but should not replace them.

Application to indicators and HMI actuators

Clause 5.1 groups indication into alerting, indication and confirmation. Tables 7 to 9 assign meanings for safety of persons, process condition and equipment state, so the same colour or signal type is not reused casually for a different message.

Clause 5.2 applies the same logic to actuation. Non-illuminated HMI actuators have specific colour rules for emergency stopping, STOP/OFF, START/ON, alternating START-STOP use and RESET. The purpose is to make the actuator’s function visible before a person presses it.

Clause 5.2.3 covers illuminated HMI actuators of types a, b and c. The light can indicate that the operator should act, confirm that an action was received, or show stepwise progress, but the standard warns against mixing the indication and confirmation meanings on the same display unless they are clearly differentiated.

Clause 5.3 applies the rules to HMI actuators shown on video display terminals. Emergency operations must remain visible and reachable from the operator’s working and operating position, which matters for adaptive interfaces where the control exists on screen rather than as a fixed device.

Annex A adds special rules for mechanical indicators. Where possible, they should be marked with IEC 60417 symbols, otherwise with IEC 60617 or ISO 7000 symbols, or with a text description or recognised abbreviation. When colour is used on its own, the general colour coding rules of Clause 5.1 apply.

What terms does oSIST prEN IEC 60073:2026 define?

• Coding - A systematic way of representing specific signals or values by another set of signals under defined rules.
• Indicator - A mechanical, optical or electrical device, or part of a device, that provides visual, acoustic or tactile information.
• Acoustic signal - A signal that uses hearing to convey information.
• Tactile signal - A signal that uses touch perception to convey information.
• Visual signal - A signal that uses vision to convey information.
• HMI actuator - The part of the human-machine interface that is directly operated by a person, such as a push-button, knob or touch sensitive screen area.
• Mechanical indicator - An indicator built into a mechanical or electromechanical switching device that shows OPEN, CLOSED or an intermediate position and is not itself an HMI actuator.
• Illuminated actuator - An HMI actuator with an integrated light source that provides a visual signal by illumination.
• human-machine interface (HMI) - A system that lets a person communicate directly with a process or equipment in order to monitor and control it.

Who uses oSIST prEN IEC 60073:2026?

oSIST prEN IEC 60073:2026 is used by technical committees when they prepare safety publications, because the foreword identifies it as a Basic safety publication. It is also used by designers and specifiers of control panels, machinery interfaces, plant control rooms and operator stations.

In practice, the main users are machine builders, electrical engineers, HMI designers, safety engineers, maintenance planners and quality or procurement teams that need a consistent signalling scheme. The standard matters wherever people need to recognise alarms, machine states, control positions or emergency functions quickly and without ambiguity.

What changed in oSIST prEN IEC 60073:2026 from the previous edition?

oSIST prEN IEC 60073:2026 is the seventh edition and it cancels and replaces the sixth edition published in 2002. The foreword states that it is a technical revision.

The documented changes are:

• the title was made gender neutral
• term definitions were updated
• the term information was added
• requirements based on outdated technology were removed
• wording was improved for clarity
• the word actuator was replaced throughout by HMI actuator

Which standards are used with oSIST prEN IEC 60073:2026?

Referenced document	What it contributes
IEC Guide 104	Framework for safety publications and basic safety publications
ISO/IEC Guide 51	General guidance for including safety aspects in standards
IEC 60027 (all parts)	Letter symbols used in electrical technology
IEC 60050(845)	Vocabulary for lighting terms
IEC 60417 (all parts)	Graphical symbols for use on equipment
IEC 60447	Man-machine interface actuating principles
IEC 60617 (all parts)	Graphical symbols for diagrams
ISO 3864	Safety colours and safety signs, including colour coding rules
ISO 7000	Graphical symbols for use on equipment
ISO 8201	Audible emergency evacuation signal
ISO 11429	Auditory and visual danger and information signals
CIE Publication No. 2-2 (TC 1.6)	Colours of light signals

The term definitions also draw on IEC 60050-181, IEC 60050-171 and IEC 60050-826 for HMI, computer-screen and emergency-stopping terminology.

What does the oSIST prEN IEC 60073:2026 document contain?

The document contains the coding rules themselves, plus the tables and examples that show how to apply them. Clause 4 and Clause 5 are the core of the standard, and Tables 2 to 10 set out the characteristics, meanings and application logic for colours, shapes, sounds and tactile signals.

Annex A gives the marking and colour rules for mechanical indicators. Annex B shows a worked example for a test station using colour and time coding, and Annex C collects examples of visual, acoustic and tactile signals so that users can see how the coding ideas translate into real indicators and actuators.

SLOVENSKI STANDARD
01-oktober-2026
Osnovna in varnostna načela za vmesnik človek-stroj, označevanje in
identifikacijo - Načela kodiranja za indikatorje in aktuatorje
Basic and safety principles for man-machine interface, marking and identification -
Coding principles for indicators and actuators
Grund- und Sicherheitsregeln für die Mensch-Maschine-Schnittstelle, Kennzeichnung -
Codierungsgrundsätze für Anzeigengeräte und Bedienteile
Principes fondamentaux et de sécurité pour l'interface homme-machine, le marquage et
l'identification - Principes de codage pour les indicateurs et les organes de commande
Ta slovenski standard je istoveten z: prEN IEC 60073:2026
ICS:
01.070 Barvno kodiranje Colour coding
13.110 Varnost strojev Safety of machinery
29.020 Elektrotehnika na splošno Electrical engineering in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

3/1785/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60073 ED7
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-08-14 2026-11-06
SUPERSEDES DOCUMENTS:
3/1695/CD, 3/1778/CC
IEC TC 3 : DOCUMENTATION, GRAPHICAL SYMBOLS AND REPRESENTATIONS OF TECHNICAL INFORMATION
SECRETARIAT: SECRETARY:
Sweden Mr Mikael Törnkvist
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
TC 3 Horizontal Basic Safety
TC 2,SC 3C,TC 9,SC 17A,TC 18,TC 22,SC 22G,SC
22H,TC 23,SC 23B,SC 23E,SC 23H,SC 23J,TC 27,TC
31,SC 31M,SC 34D,SC 37A,TC 44,SC 45A,TC 61,TC
62,TC 64,SC 65B,TC 66,TC 69,TC 72,TC 79,TC 80,TC
85,TC 88,TC 96,TC 100,TC 108,TC 116,SC 121A,SC
121B
ASPECTS CONCERNED:
Safety
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submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Basic and safety principles for man-machine interface, marking and identification - Coding principles
for indicators and actuators
PROPOSED STABILITY DATE: 2032
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IEC CDV 60073 © IEC 2026
CONTENTS
Contact . 2
CONTENTS . 1
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Coding principles . 9
4.1 General . 9
4.2 Visual signals . 11
4.2.1 General . 11
4.2.2 Coding by colours . 11
4.2.3 Codingby shapes or position or both . 13
4.2.4 Coding by changing of characteristics over time . 14
4.3 Acoustic signals . 14
4.4 Tactile signals . 15
5 Application requirements . 16
5.1 Indication modes . 16
5.2 Actuation modes . 7
5.2.1 General . 7
5.2.2 Non-illuminated HMI actuators . 7
5.2.3 Illuminated HMI actuators . 8
5.3 HMI actuators as a part of pictorial presentation on a video display terminal . 9
5.3.1 Identification of HMI actuators . 9
5.3.2 Emergency operations . 9
Annex A (normative) Special requirements for mechanical indicators . 10
A.1 Marking . 10
A.2 Colours . 10
A.2.1 Mechanical indicators with graphical symbols or words . 10
A.2.2 Mechanical indicators without graphical symbols or words . 10
Annex B (informative) Example for the application of indication coding (using colours) . 11
Annex C (informative) Examples of visual, acoustic and tactile signals . 13
Bibliography . 16

Figure B.1 – Indicators and actuators associated with a test station . 11

Table 1 – . 4
Table 2 – Means of coding and their characteristics to be considered . 10
Table 3 – Meaning of colours – General principles . 12
Table 4 – Meaning of shapes – General principles . 13
Table 5 – Meaning of acoustic codes – General principles . 15
Table 6 – Meaning of tactile signals – General principles . 16
Table 7 – Meaning of indication signals with respect to the safety of persons, property
aor the environment . 1
IEC CDV 60073 © IEC 2026
Table 8 – Meaning of indication signals with respect to the condition of the process . 2
Table 9 – Meaning of indication signals with respect to the state of equipment . 4
Table 10 – General meaning of the signals for HMI actuators . 5
Table B.1 – Information to be coded . 12
Table B.2 – Complete information concept for the example . 12
Table C.1 – Examples of visual signals . 13
Table C.2 – Examples of acoustic signals . 14
Table C.3 – Examples of tactile signals . 15

IEC CDV 60073 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Basic and safety principles for man-machine interface, marking and
identification - Coding principles for indicators and actuators

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 itself does not provide any attestation of conformity. Independent certification bodies
provide conformity assessment services and, in some areas, access to IEC marks of conformity.
IEC is not responsible for any services carried out by independent certification bodies.
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) IEC draws attention to the possibility that the implementation of this document may involve
the use of (a) patent(s). IEC takes no position concerning the evidence, validity or applicability
of any claimed patent rights in respect thereof. As of the date of publication of this document,
IEC [had/had not] received notice of (a) patent(s), which may be required to implement this
document. However, implementers are cautioned that this may not represent the latest
IEC CDV 60073 © IEC 2026
information, which may be obtained from the patent database available at https://patents.iec.ch.
IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60073 has been prepared by IEC technical committee 3: Basic and
safety principles for man-machine interface, marking and identification. It is an international
standard.
This seventh edition cancels and replaces the sixth edition published in 2002. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the title of the document has been modified to be gender neutral
b) definition of terms has been updated
c) definition of the term "information" is provided
d) requirements based on out-dated technology has been removed;
e) wording improved to make requirements clearer;
f) the word "actuator" is replaced by "HMI actuator" throughout the document.
It has the status of a Basic safety publication in accordance with IEC Guide 104.
The text of this International Standard is based on the following documents:
Table 1 –
FDIS Report on voting
3/XX/FDIS 3/XX/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English [change
language if necessary].
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
Annex A forms an integral part of this standard.
Annex B and Annex C are for information only.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
IEC CDV 60073 © IEC 2026
INTRODUCTION
Supervision and intervention are the principal tasks of personnel engaged in the monitoring and
control of equipment or processes.
Indicators for the representation of conditions, and actuating devices to enable intervention
under normal and fault conditions, are essential to this purpose.
The information presented should meet the needs of the users for the monitoring and control
tasks which they are required to perform, for example, in extensive industrial processes.
Safety and ergonomic aspects should also be taken into account. The use of only a single
means of coding is often insufficient to ensure unambiguous representation of information.
Apart from an unambiguous marking of the indicating and actuating devices, there is a
requirement for a clear and consistent system of coding.
The choice of a code will depend on the information which it is intended to impart. This may
relate to the state of equipment (or part of it), to the condition of a process, and/or to the effects
which this condition has on persons, property and the environment.
The user is required to decide on which of these criteria the coding for the relevant application
is to be based.
IEC CDV 60073 © IEC 2026
1 Scope
This International Standard establishes general rules for assigning particular meanings to
certain visual, acoustic and tactile indications in order to
a) increase the safety of persons, property or the environment through the safe monitoring and
control of the equipment or process;
b) facilitate the proper monitoring, control and maintenance of the equipment or process;
c) facilitate the rapid recognition of control conditions and HMI actuator positions.
This standard is for general application:
– from simple cases such as single indicator lights, push-buttons, mechanical indicators, light
emitting diodes (LEDs) or video display screens to extensive control stations which may
include a wide variety of devices for controlling an equipment or process;
– where the safety of persons, property or the environment is involved, and also where the
above-mentioned codes are used to facilitate the proper monitoring and controlling of
equipment;
– where a particular kind of coding is to be assigned by a technical committee to a special
function.
This BASIC SAFETY PUBLICATION focusing on SAFETY essential requirement is primarily
intended for use by technical committees in the preparation of SAFETY publications in
accordance with the principles laid down in IEC Guide 104 and ISO/IEC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications in the preparation of its publications.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 Guide 104, The preparation of safety publications and the use of basic safety publications
and group safety publications
IEC 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050(845), International Electrotechnical Vocabulary (IEV) Lighting
IEC 60417 (all parts), Graphical symbols for use on equipment
IEC 60447, Man-machine interface (MMI) – Actuating principles
IEC 60617 (all parts), Graphical symbols for diagrams
ISO/IEC Guide 51, Safety aspects – Guidelines for their inclusion in standards
ISO 3864, Safety colours and safety signs
ISO 7000, Graphical symbols for use on equipment – Index and synopsis
ISO 8201, Acoustics – Audible emergency evacuation signal
IEC CDV 60073 © IEC 2026
ISO 11429, Ergonomics – System of auditory and visual danger and information signals
CIE (International Commission on Illumination): Publication No. 2-2 (TC 1.6), Colours of light
signals
3 Terms and definitions
For the purposes of this standard, the following definitions apply.
3.1
coding
systematic representation of specific signals or values by another set of signals, which
has to conform to a definite set of rules
[SOURCE: IEC 660050-181:—, 181-14-11]
3.2
indicator
mechanical, optical or electrical device or a part of device providing visual, acoustic or tactile
information
[SOURCE: IEC 60050-181:—, 181-14-12]
3.3
acoustic signal
audible signal
phenomenon utilizing auditory perception in humans to convey information
[SOURCE: IEV 60050-181:—, 181-14-09, modified — The synonym added.]
3.4
tactile signal
phenomenon utilizing tactile perception in humans to convey information
[SOURCE: IEV 60050-181:—, 181-14-10]
3.5
visual signal
phenomenon utilizing visual perception in humans to convey information
[SOURCE: IEV 60050-181:—, 181-14-08]
3.6
HMI actuator
part of the human-machine interface which is subject to a direct human intervention
EXAMPLE Knob, push-button, push-push button, push-pull button, roller, plunger, mouse, light pen, keyboard,
touch sensitive screen, voice actuator.
Note 1 to entry: For the purposes of this standard, the HMI actuator in the case of an interactive screen display is
considered to be that part of the screen display which represents the HMI actuator function.
[SOURCE: IEC 60050-181:—, 181-14-02]
IEC CDV 60073 © IEC 2026
3.7
mechanical indicator
indicator, forming an integral part of a mechanical or electromechanical switching device, that
indicates whether the switching device is in the OPEN, CLOSED or an intermediate position,
and is not intended as an HMI actuator
[SOURCE: IEC 60050-181:—, 181-14-13]
3.8
human-machine interface
HMI
system enabling a direct means of communication between a human and a process or
equipment, enabling the human to monitor and control the equipment or process
Note 1 to entry: Such systems can include manually operated HMI actuators, indicators and screens
[SOURCE: IEC 60050-181:—, 181-14-01]
3.9
signal light
device designed to emit a light signal
[SOURCE: IEC 60050-845:2020, 845-31-004]
3.10
light emitting diode
LED
solid-state device embodying a p-n junction, emitting optical radiation when excited by an
electric current
[SOURCE: IEC 60050-845:2020, 845-27-050, modified - Notes to entry removed.]
3.11
illuminated actuator
HMI actuator with an integrated light source providing a visual signal by illumination
Note 1 to entry: The operation of the light source can be related to or independent of the HMI actuator action.
[SOURCE: IEC 60050-181:—, 181-14-06]
3.12
hue
attribute of a visual perception according to which an area appears to be similar to one of the
colours red, yellow, green, and blue, or to a combination of adjacent pairs of these colours
considered in a closed ring
[SOURCE: IEC 60050-845:2020, 845-22-067, modified - Note 1 to entry removed.]
3.13
brightness
attribute of a visual perception according to which an area appears to emit, transmit or reflect,
more or less light
[SOURCE: IEC 60050-845:2020, 845-22-059, modified - Notes to entry removed.]
3.14
saturation
colourfulness of an area judged in proportion to its brightness
IEC CDV 60073 © IEC 2026
Note 1 to entry: For given viewing conditions and at luminance levels within the range of photopic vision, a colour
stimulus of a given chromaticity exhibits approximately constant saturation for all luminance levels, except when the
brightness is very high.
[SOURCE: IEC 60050-845:2020, 845-22-073, modified - Note 2 to entry removed.]
3.15
contrast
perceived contrast
assessment of the difference in appearance of two or more parts of
a field seen simultaneously or successively
EXAMPLE Brightness contrast, lightness contrast, colour contrast, simultaneous contrast, successive contrast
[SOURCE: IEC 60050-845:2020, 845-22-089, modified - Note 1 to entry removed.]
3.16
information
knowledge represented for communication, storage or processing
Note 1 to entry: Information can be represented, for example, by signs, symbols, pictures or sounds.
[SOURCE: IEC 60050-181:—, 181-01-03]
3.17
computer screen
video display terminal
screen
display
monitor
VDT
device that gives a visual representation of data
[SOURCE: IEC 60050-171: 2019, 171-04-39, modified – visual display terminal and VDT added
as synonyms and "output device" replaced by "device".]
3.18
emergency switching-off
operation intended to initiate the remove electric power from an equipment, machine, system
or installation to avert or alleviate a hazardous situation
[SOURCE: IEC 60447:—, 3.20]
3.19
emergency stopping
operation intended to stop as quickly as possible a movement which has become dangerous
[SOURCE: IEC 60050-826:2022, 826-17-03]
4 Coding principles
4.1 General
Coding principles shall be established at an early stage of system design and shall be consistent
with those used for other equipment within the same plant or process.
For the selection of a specific code, consideretions shall be taken to the task to be performed
of the personell and the operating conditions.
IEC CDV 60073 © IEC 2026
One or more of the following means of indication coding should be applied:
Visual signals:
– by colour;
– by shape;
– by position;
– by changing characteristics over time (flashing).
Acoustic signals:
– by type of sound;
– by pure tone;
– by changing characteristic over time.
Haptic signals:
– by shape;
– by force;
– by vibration;
– by position;
– by changing characteristic over time.
Table 2 provides examples of characteristics to be considered for different codings
The meaning of the selected codes shall be unambiguous and shall be explained in the
associated documentation of the equipment , process or plant.
Table 2 – Means of coding and their characteristics to be considered
Means Characteristic
Visual signals
– Hue
Colour
– Saturation
– Brightness
– Contrast
– Figure (alphanumeric, pictographs, graphical symbols, lines)
Shape
– Form (character font, size, line width)
– Texture (line type, shading, dotting)
– Location (absolute, relative)
Position
– Orientation (with or without reference system)
Time Changing over time (flashing):
– Brightness
– Colour
– Shape
– Position
Acoustic signals
– Tone
Type of sound
– Noise
– Spoken message
– Selected frequency
Pure tone
IEC CDV 60073 © IEC 2026
Means Characteristic
Time Change of
– Frequency composition over time
– Sound volume over time
– Total duration
Tactile signals
– Form
Shape
– Surface roughness
– Amplitude
Force
– Amplitude
Vibration
– Frequency
– Location (absolute, relative)
Position
– Orientation (with or without reference system)
Time Change of:
– Force over time
– Vibration over time
4.2 Visual signals
4.2.1 General
For visual signals, colour and changing of elements over time (flashing) are the most effective
visual means of attracting attention. Therefore these means shall be used with consistent
meanings; colours for giving priority and flashing for attracting attention.
Colour shall not be the sole means of coding. The colour shall be within the chromaticity
boundary specified in ISO 3864-4 during the expected life of the indicators and HMI actuators
under the specified operating conditions.
Where the meaning of colour relates to the safety of persons or the environment (see 4.2.2.2)
supplementary means of coding shall be provided.
Where operating conditions prohibit the application a colour with a specific information, either:
– other means for visual signals (see 4.2.3), or
– other indication methods (see the following subclauses of Clause 4),
shall be provided
4.2.2 Coding by colours
4.2.2.1 General
Specific meanings are assigned to specific colours (see Table 3) and these colours shall be
easily identifiable and distinguishable from the background colour and any other assigned
colours. Certain colours are reserved for safety applications.
The number of colours used in a given application should be kept to a minimum.
The following colours for indicators and HMI actuators are specified in this document:
RED, YELLOW, GREEN, BLUE, BLACK, GREY, WHITE.
Other colours may be used but their meanings are not defined in this document.
IEC CDV 60073 © IEC 2026
A colour shall be specified by an appropriate combination of íts hue, saturation, brightness or
contrast charactistics in accordance with the requirements of ISO 3864 series.
Where colour is the sole means of coding, the colour shall be within the chromaticity boundary
specified in ISO 3864-4 during the expected life of the indicators and HMI actuators under the
specified operating conditions.
For the exact definitions see:
– for surface colours:, see ISO 3864;
– for emitted lights, see CIE S 004/E:2001
NOTE 1 Perceived colour is due to the combined effects of emitted light, if any (e.g. of a signal light) and incident
light (e.g. of the working place).
NOTE 2 The colour GREY is not defined in ISO 3864.
4.2.2.2 Choice of colours
The general principles for the meaning of colours for the indication of information are specified
in Table 3.
Table 3 – Meaning of colours – General principles
Colour Meaning
Safety of persons or Condition of process State of equipment
environment
RED Danger Emergency Faulty
YELLOW Warning/caution Abnormal Abnormal
GREEN Safe Normal Normal
BLUE Mandatory significance
WHITE No specific meaning assigned
GREY
BLACK
Where indicators connected in parallel, mounted at different locations, have different meanings
in their location context, different colours may be used for the indicators (see Annex B).
The colour to be displayed by indicators shall be chosen with regard to the information to be
imparted.
The colour coding shall be selected according :
– Table 7 when the coding is related to safety of persons or the environment;
– Table 8 when the coding is related to the condition of the process;
– Table 9 when the coding is related to state of the equipment.
The colour coding applied shall not shall cause risk of confusion
4.2.2.3 Colours on video display screens
The application of colours listed in 4.2.2.1 shall be restricted to that purpose as given in 4.2.2.2.
Other kind of information may be transmitted using other colours provided no misunderstanding
may arise.
Colours shall contrast adequately with adjacent colours and with the background of the display.
oSIST prEN
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