kSIST FprES 203 408 V1.2.1:2026

• Abstract:

  RES/EE-02111

• Status: Not Published
• ICS: 01.070 - Colour coding
• ICS: 19.040 - Environmental testing
• ICS: 29.060.20 - Cables
• Technical Committee: SPN - Services and Protocols for Networks
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 10-Aug-2026
• Due Date: 28-Sep-2026
• Completion Date: 10-Aug-2026
• Ref Project: ETSI ES 203 408 V1.2.1 (2026-08) - Environmental Engineering (EE); Colour and marking of DC cable and connecting devices

Overview

kSIST FprES 203 408 V1.2.1:2026, developed by SIST and aligned with ETSI standards, addresses best practices for the colour and marking of DC cables and connecting devices, specifically for telecom and ICT infrastructure up to 400 VDC. This standard aims to ensure the safe and unambiguous identification of DC power distribution components in data centers, telecom sites, and corresponding facilities. By following established norms such as IEC 60445, it minimizes risks, avoids confusion with AC systems, and facilitates installation and maintenance operations for operators, manufacturers, installers, and end-users.

Key Topics

• Cable and Conductor Identification:
  Ensures clear marking and consistent use of colours, graphical symbols, and alphanumeric labels for individual conductors, multiwire cables, and connectors throughout ICT and facility installations.

• Harmonization with International Standards:
  Emphasizes alignment with existing IEC (e.g., IEC 60445, IEC 60757) and ITU-T L.1200/L.1203 recommendations for global interoperability and safety.

• Scope and Application:
  Covers DC power distribution for interfaces up to 400 VDC (A3 or P), existing -48 VDC systems (A), and distinguishes these from AC power systems, including specific protocols for new installations, extensions, or modifications.

• Avoiding Ambiguity and Error:
  Mandates the use of clear and non-ambiguous identifiers, helping reduce wiring errors, promote safety, and streamline site management, especially where AC and different DC voltages coexist.

• Marking of Distribution Devices:
  Requires uniform marking for distribution boxes, sub-distribution boards, and interconnection boxes, including use of both colour coding and textual labels in line with IEC and ETSI guidance.

Applications

Practical benefits and use cases for this standard include:

• Telecommunications Sites and Data Centers:
  Reliable management and identification of complex DC cabling networks, supporting both legacy (-48 VDC) and modern (up to 400 VDC) power architectures.

• Facility and Building Services:
  Mitigates risks associated with misidentification in environments where AC and DC systems are in proximity, aiding installers and maintenance staff.

• Equipment Manufacturing and System Integration:
  Provides a clear framework for manufacturers to mark cables and connectors, enhancing product safety and user understanding, and streamlining certification processes.

• Upgrades and Expansions:
  Facilitates seamless expansion or modification of existing infrastructure by prescribing how new and existing colour and marking schemes should coexist and be documented.

• International Projects:
  Promotes interoperability for multinational deployments by harmonizing identification practices with widely accepted international norms.

Related Standards

Organizations implementing kSIST FprES 203 408 V1.2.1:2026 may also refer to the following complementary standards:

• IEC 60445:
  Basic and safety principles for man-machine interface, marking and identification of equipment terminals, conductor terminations, and conductors.
• IEC 60757:
  Code for the designation of cable and conductor colours.
• IEC 60417/IEC 60617:
  Graphical symbols for use on equipment and diagrams, supporting visual clarity in marking.
• ETSI EN 300 132-2/-3:
  Environmental Engineering standards for DC power supply interfaces in ICT equipment (-48 VDC and up to 400 VDC).
• ETSI EN 300 253 & EN 301 605:
  Earthing and bonding of ICT equipment powered by DC voltages.
• Recommendation ITU-T L.1200 & L.1203:
  Cover technical guidelines for DC power interfaces and colour identification.
• IEC 60050-195:
  Terminology and vocabulary relating to earthing and electric shock protection.

By adhering to this ETSI-aligned standard, stakeholders in telecommunications, data centers, and related infrastructure projects ensure compliance, increase operational safety, and facilitate efficient maintenance and upgrades of DC power systems.

Final draft ETSI ES 203 408 V1.2.1 (2026-08)

ETSI STANDARD
Environmental Engineering (EE);
Colour and marking of DC cable and connecting devices

2 Final draft ETSI ES 203 408 V1.2.1 (2026-08)

Reference
RES/EE-02111
Keywords
cable, identification, power
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ETSI
3 Final draft ETSI ES 203 408 V1.2.1 (2026-08)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 5
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definitions, symbols and abbreviations . 9
3.1 Definitions . 9
3.2 Symbols . 9
3.3 Abbreviations . 9
4 Electrical Distribution identification coverage . 10
5 Identification principle . 12
5.1 General rules . 12
5.2 Colour and marking of up to 400 VDC conductor wires and cables for A3 or P interface . 13
5.3 Additional recommendations for other DC voltage distribution cabling excluding up to 400 VDC
interface A3 or P . 15
6 DC distribution devices additional colour and marking . 15
6.0 Colour and marking of up to 400 VDC distribution devices, other than wires and cables . 15
6.1 General requirements . 16
6.2 DC outputs from DC power systems with protective devices . 16
6.3 DC sub-distribution boards (with protective devices) . 17
6.4 DC power plugs strips inside ICT equipment rooms and cabinets . 17
7 Durability of Marking and reading errors limitation . 17
Annex A (informative): Review of Standards or common use of colour and marking of
distribution cabling in AC and DC in buildings and equipment . 18
A.1 Recommended colours for wires in IEC 60757 and IEC 60445 . 18
A.2 Other Norms or specifications . 18
A.2.0 Introduction . 18
A.2.1 Single and bicolour cables used in transportation sector . 18
A.2.2 Cables used in flying aircrafts, ground works machines and boats . 19
A.2.3 Colour of personal computer power cables . 19
A.2.4 Machine Cabling . 19
A.2.5 Family of cables coding . 19
A.3 Building distribution cable colour and marking standards . 20
A.3.1 Introduction . 20
A.3.2 Low frequency cable and wire reference insulation colour in IEC 60304 . 21
A.3.3 IEC 60445 . 21
A.3.3.0 General information on IEC 60445 . 21
A.3.3.1 Old Cable Colour Code reminder . 21
A.3.3.2 Harmonized Cable colours . 21
A.3.3.3 Marking and alteration for cohabitation of harmonized and old Cable colours . 21
A.3.4 DC coding evolution . 22
A.3.4.1 Colours and marking of DC cables in the UK . 22
A.3.4.2 Colours and marking of DC cables in China . 22
A.3.4.3 Colours and marking of DC cables in Republic of Korea . 23
Annex B (informative): Bibliography . 24
ETSI
4 Final draft ETSI ES 203 408 V1.2.1 (2026-08)
History . 25

ETSI
5 Final draft ETSI ES 203 408 V1.2.1 (2026-08)
Intellectual Property Rights
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Foreword
This final draft ETSI Standard (ES) has been produced by ETSI Technical Committee Environmental Engineering (EE),
and is now submitted for the ETSI Membership Approval Procedure (MAP).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The present document has been developed to assist the ICT industry in their development and wider use of DC
powering solutions above the DC voltage range mainly used until now for Telecommunication network equipment
(-48 VDC ETSI EN 300 132-2 [7]).
The present document has been jointly developed by ETSI TC EE and ITU-T Study Group 5 in order to ensure
equivalent technical content. It is published respectively by ITU as Recommendation ITU-T L.1203 [1] and ETSI
Standard ETSI ES 203 408.
DC power has been the main source of power for the Telecommunication industry since the very beginning as it is
efficient, reliable and easily scalable.
ETSI
6 Final draft ETSI ES 203 408 V1.2.1 (2026-08)
This solution is a well proven arrangement that has been used for over a century in almost all telecommunication
network equipment sites in cohabitation with AC for servers and other buildings services (lighting, facility plugs, lifts,
etc.).
It is recognized that DC power has many potential applications further to those for ICT equipment and that such
applications could benefit from the standards defined in ITU/ETSI. It is also recognized that further standardization
activities on LVDC are now starting in other standardization organizations such as IEC. Thus ITU-T/ETSI will pursue
cooperation with such organizations to reach maximum international alignment.
ETSI and ITU-T have standardized the widespread DC power interface at inputs of Telecom/ICT equipment used in
Telecom networks, Data centers, and customer sites. The legacy interface for billions of equipment is the SELV voltage
range so called -48 VDC, where the positive pole is grounded as defined for example for interface "A" in ETSI
EN 300 132-2 [7]. Other complementary ETSI standards define a whole DC distribution including earthing and bonding
such as ETSI EN 300 253 [9].
Higher voltages than -48 VDC are already widely used in Telecom networks for remote powering of signal repeaters on
copper or optical Telecom transmission lines, with a usual operation in symmetrical voltage up to ±200 V in RFT-C or
RFT-V telecom remote power feeding standardized in ETSI EN 302 099 [i.1].
The higher power density of ICT equipment and overall site power in MW for Data centers have led to the use of higher
voltage levels, firstly in AC single or 3 phases up to 400 VAC at the input of servers. The need for resilience, energy
efficiency and cost optimization has pushed the introduction of the up to 400 VDC power feeding interface standardized
in ETSI EN 300 132-3 [8] and in Recommendation ITU-T L.1200 [2]. This is now available on many servers and
Telecommunication network equipment.
As there is a progressive introduction of the new DC power interface in cohabitation with existing -48 VDC and AC
distribution, ETSI EN 301 605 [10] has been introduced to ensure safety and proper operation, especially in mass
bonding of EMC sensitive equipment and correct earthing connection to the building structure earthing network.
There is also a requirement for Telecom/Data center operators, equipment manufacturers, installers and end customers
to clarify the colour and marking of cables in their installations. This avoids confusion and errors between the different
AC and DC power interfaces and distribution equipment used in the building and inside ICT systems.
Considering the user side, and very long background experience in use of DC of the Telecom sector, the present
document makes recommendations directly contributing to safety principles laid down in IEC Guide 104 [i.9] and
ISO/IEC Guide 51 [i.10]. It accelerates and encourages the preparation of international standards of cable identification
intended for use by manufacturers, users or certification bodies.
With reference to safety, it is important there is no ambiguity with respect to cable colours and identification. The
present document therefore recommends harmonisation with existing IEC standards including IEC 60445 [3] and
IEC 60050-195 [i.2], allowing a standardized industry approach.
For useful information, colours of cables inside equipment are considered in annex A as DC is already widely used for a
multitude of applications, e.g. ICT equipment, car and trucks electric circuits, solar PV, etc.
ETSI
7 Final draft ETSI ES 203 408 V1.2.1 (2026-08)
1 Scope
The scope of the present document is to define common practice for identification of cabling or parts of the DC power
distribution for the Telecom sites (buildings/rooms) feeding ICT and facilities equipment (power plant, cooling,
building access systems, monitoring, etc.).
This applies to 400 VDC cabling for ICT equipment and environment equipment using interface defined in ETSI
EN 300 132-3 [8] or Recommendation ITU-T L.1200 [2] and avoids confusion between the DC colour and marking of
up to 400 VDC distribution (interface A3) and the other power interfaces identification: -48 VDC distribution interface
A, AC interface A1 and uninterrupted AC given by inverters or UPS systems used in the building.
To ensure safety, it is important there is no ambiguity with respect to cable colours and identification, The present
document therefore recommends harmonisation with existing IEC standards including IEC 60445 [3] and
IEC 60050-195 [i.2], allowing a standardized industry approach.
The Recommendation defines:
• requirements for the colour and identification of separate wires used in DC distribution systems and
installations, and as much as possible inside equipment between A or P interface and end use;
• marking and identification of DC multiwire cables, connectors and any associated equipment for DC power
distribution;
• marking identification for sui-distribution boards and interconnection boxes;
• harmonisation with IEC 60445 [3].
For DC wires in multiwire cables, recommendations are given for harmonization with separate individual wire
requirements.
Recommendations are given on other distribution items (wires, cables and interconnection items) including the
functional earthing and bonding arrangement for distribution outside and inside equipment to avoid any confusion with
DC distribution identification of the present document.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found in the
ETSI docbox.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long-term validity.
The following referenced documents are necessary for the application of the present document.
[1] Recommendation ITU-T L.1203: "Colour and marking identification of up to 400VDC power
distribution for ICT systems".
[2] Recommendation ITU-T L.1200 (2012): "Direct current power feeding interface up to 400 V at the
input to telecommunication and ICT equipment".
[3] IEC 60445:2021: "Basic and safety principles for man-machine interface, marking and
identification - Identification of equipment terminals, conductor terminations and conductors".
[4] IEC 60757:2021: "Code for designation of colours".
ETSI
8 Final draft ETSI ES 203 408 V1.2.1 (2026-08)
[5] IEC 60417:2026 DB: "Graphical symbols for use on equipment".
[6] IEC 60617:2026 DB: "Graphical symbols for diagrams".
NOTE: IEC DB documents refer to Database of Graphical Symbol. Some are joint with ISO e.g. IEC 60417 and
ISO 7000.
[7] ETSI EN 300 132-2 (V2.8.1): "Environmental Engineering (EE); Power supply interface at the
input of Information and Communication Technology (ICT) equipment; Part 2: -48 V Direct
Current (DC)".
[8] ETSI EN 300 132-3 (V2.3.1): "Environmental Engineering (EE); Power supply interface at the
input of Information and Communication Technology (ICT) equipment; Part 3: Up to 400 V
Direct Current (DC)".
[9] ETSI EN 300 253 (V2.2.1): "Environmental Engineering (EE); Earthing and bonding of ICT
equipment powered by -48 VDC in telecom and data centres".
[10] ETSI EN 301 605 (V1.1.1): "Environmental Engineering (EE); Earthing and bonding of 400 VDC
data and telecom (ICT) equipment".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long-term validity.
The following referenced documents may be useful in implementing an ETSI deliverable or add to the reader's
understanding, but are not required for conformance to the present document.
[i.1] ETSI EN 302 099 (V2.3.1): "Environmental Engineering (EE); Powering of equipment in access
network".
[i.2] IEC 60050-195 (2021): "IEC Terminology International Electrotechnical Vocabulary - Part 195:
Earthing and protection against electric shock".
[i.3] IEC 60050-826 (2022): "International Electrotechnical Vocabulary - Part 826: Electrical
installations".
[i.4] BS 7671/A4 (2026): "Requirements for Electrical Installations. IET Wiring Regulations".
[i.5] HD 308 S2:2001: "Identification of cores in cables and flexible cords".
[i.6] HD 324 S1 (withdrawn) (1977): "Colored insulation and bare wire identification package".
[i.7] HD 384.5.514 (withdrawn): "Identification, including 514.3: Identification of conductors".
[i.8] IEC 60364-1 (2025): "Low-voltage electrical installations - Part 1: Fundamental principles,
assessment of general characteristics, definitions".
[i.9] IEC Guide 104: "The preparation of safety publications and the use of basic safety publications
and group safety publications".
[i.10] ISO/IEC Guide 51: "Safety aspects - Guidelines for their inclusion in standards".
[i.11] ISO 19642 (2023): "Road vehicles. Automotive cables".
[i.12] ISO 2574 (1994): "Flying machine electric cable - Identification marking".
[i.13] ISO 9247 (1990): "Ground work machine - electric wire and cables -- identification and marking
principles".
ETSI
9 Final draft ETSI ES 203 408 V1.2.1 (2026-08)
[i.14] IEC EN 60204-1 (2018): "Safety of machinery -Electrical equipment of machines -Part 1:General
requirements".
[i.15] IEC 60304 (1982): "Standard colours for insulation for low-frequency cables and wires".
[i.16] Void.
[i.17] Void.
[i.18] Void.
[i.19] IEC 60446 (withdrawn) (2007): "Basic and safety principles for man-machine interface, marking
and identification - identification of conductors by colours or alphanumerics".
[i.20] CCSA YD/T 2378 (2020): "240V Direct Current Power supply system for Telecommunications".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
cable identification: colour, graphical symbol, text in alphanumeric notation located on or adjacent to wire or cable
terminals or junction boxes
electrical equipment: item used for purposes like generation, conversion, distribution or utilization of electric energy
(e.g. electrical machines, transformers, switch gear and control gear, measuring instruments, wiring systems,
current-using equipment, etc.) (IEC 60050-826 [i.3])
IT (Isolation Terra): Isolation Terra earthing as defined in IEC 60364-1 [i.8].
NOTE: The two letters IT are coding one of the 3 families of electrical distribution where connection to earth is
made through high resistance or impedance device i.e. HRMG in ETSI EN 301 605 [10].
line conductor: AC phase conductor or DC pole conductor (deprecated) conductor which is energized in normal
operation and capable of contributing to the transmission or distribution of electric energy but which is not a neutral
conductor (IEC 60050-195 [i.2])
TN-S DC: Distribution earthing arrangements as defined in IEC 60364-1 [i.8] and ETSI EN 301 605 [10] where earth
and negative (DC) wires are separated
3.2 Symbols
For the purposes of the present document, the following symbols apply:
48 VDC -48 Volt Direct Current voltage as defined in ETSI EN 300 132-2 [7]
400 VDC up to 400 Volt Direct Current voltage as defined in Recommendation ITU-T L.1200 [2]
A (interface) ICT/Telecom equipment -48 VDC power interface as defined in in ETSI EN 300 132-2 [7]
A3 (interface) ICT/Telecom equipment up to 400 VDC power interface as defined in ETSI EN 300 132-3 [8]
P ICT/Telecom equipment up to 400 VDC power interface as defined in Recommendation
ITU-T L.1200 [2]
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternative Current
DC Direct Current
EMC Electro Magnetic Compatibility
HRMG High Resistance Mid-point Grounding
ETSI
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