kSIST FprEN IEC 60297-3-103:2026

• Status: Not Published
• Public Enquiry End Date: 31-Jan-2026
• ICS: 31.240 - Mechanical structures for electronic equipment
• Technical Committee: I11 - Imaginarni 11
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 17-Aug-2026
• Due Date: 05-Oct-2026
• Completion Date: 21-Aug-2026
• Ref Project: FprEN IEC 60297-3-103:2026 - Mechanical structures for electrical and electronic equipment - Dimensions of mechanical structures of the 482,6 mm (19 in) series - Part 3-103: Keying and alignment pin

• Revises: SIST EN 60297-3-103:2005 - Mechanical structures for electronic equipment - Dimensions of mechanical structures of the 482,6 mm (19 in) series -- Part 3-103: Keying and alignment pin
• Effective Date: 22-Jul-2025

SIST’s kSIST FprEN IEC 60297-3-103:2026 is the Slovenian publication for the IEC 60297 series on mechanical structures for electronic equipment in the 482,6 mm (19 in) format. It specifies the additional interface dimensions for a keying device and an alignment pin used with subracks and plug-in units, so that compatible units can be guided, coded and fitted correctly.

What does kSIST FprEN IEC 60297-3-103:2026 specify?

kSIST FprEN IEC 60297-3-103:2026 covers only the extra interface dimensions for alignment pin and keying features used with subracks and plug-in units according to IEC 60297-3-101. The document is organised into clauses 1 to 7, with figures that show the arrangements and one table for inspection dimensions.

The part is written for the conventional 19-inch subrack system. It works with the base dimensions in IEC 60297-3-101 and may also be used together with IEC 60297-3-102 for injector/extractor handle arrangements.

What are the key requirements of kSIST FprEN IEC 60297-3-103:2026?

Keying to prevent wrong insertion

Clause 4.1 says the keying arrangement is used to prevent misarrangement of board-type plug-in units in subracks. The keys are snap-in mounted so they can be changed or retrofitted, and the plug-in unit and the subrack guide rail both need a special retainer.

In practice, this is the mechanical coding that stops an incompatible plug-in unit from being inserted. That matters for system integrity, service work and field upgrades, because the wrong module can be blocked before it reaches the backplane or front-panel position.

Key positions and programming

Clause 4.4 says the key dimensions allow four positions within a subrack mounting chamber. The key is designed as a self-retaining snap-in part.

For 3U subracks, the document recommends keying on the lower side only. For 6U and 9U, keying on both the upper and lower side is needed. Clause 4.5 then explains that matching keying chambers are identified by the same letters, and that a matching identification number keeps insertion possible while a different one blocks insertion.

In practice, installers and designers must use the correct chamber coding, not just the correct physical part. That is what makes the keying system an actual fit-and-block mechanism rather than a visual label.

Keying chamber inspection

Clause 4.6 and Table 1 give the inspection dimensions for the subrack and plug-in unit keying chambers for 3U, 6U and 9U cases. The note points readers to IEC 60297-3-101 for bracketed and missing dimensions.

In practice, this is the part used for production checks and incoming inspection. It tells a manufacturer or quality team what to verify when checking whether the keying chamber will accept the intended plug-in unit.

Alignment and/or electrical contact

Clause 5.1 says the alignment and/or electrical contact feature is used either to keep front panels at a controlled distance in a subrack, for example when shielding gaskets are used, or to provide an electrical contact to the receptacle in the subrack.

In practice, this feature serves two jobs: it helps with mechanical alignment and it can provide grounding or contact continuity. That matters when the front panel must sit at a defined spacing or when the design needs contact to chassis ground.

Receptacle and contact details

Clause 5.2 covers the alignment and/or electrical contact receptacle in the subrack guide rail for printed board type plug-in units with width dimension ≥ 4 × 5,08 mm. The receptacle may be part of the guide rail, the hole guides the alignment pin, and within a defined 5 mm area an earth contact may be used to connect the pin to chassis ground.

In practice, designers use this clause to shape the rail, locate the hole and decide whether to add the earth contact. That is important when the alignment feature also has to support electrical bonding.

2,54 mm offset guide rail arrangement

Clause 6.1 says the guide rail offset does not change the position in the subrack, but it shifts the groove for the printed board 2,54 mm to the right. Clauses 6.2 and 6.3 give the related dimensions and the reference plane for printed boards with that offset position.

In practice, this gives a second mechanical arrangement for printed-board location without moving the rail in the rack. It is useful when a system needs a different board reference plane but must stay compatible with the subrack layout.

What terms does kSIST FprEN IEC 60297-3-103:2026 define?

• U - The coordination height unit, equal to 44,45 mm (1,75 in), used to describe rack height in this series.
• H - The mounting centre distance for plug-in units, front panels, backplanes and connector supports.
• Subrack - The rack frame that receives plug-in units and provides the mechanical interface described in the document.
• Plug-in unit - The inserted unit that mates with the subrack through the specified keying, alignment or guide-rail interfaces.
• Keying - The mechanical coding arrangement that prevents the wrong plug-in unit from being inserted into a subrack.
• Alignment pin - The pin and matching receptacle used to guide positioning and, where required, provide electrical contact.
• Guide rail - The rail that guides the plug-in unit or printed board and can also carry the alignment or contact feature.

Who uses kSIST FprEN IEC 60297-3-103:2026?

kSIST FprEN IEC 60297-3-103:2026 is used by engineers who design 19-inch subracks, plug-in units, front panels and guide rails. It is also used by manufacturers and assemblers who machine the keying chambers, fit the snap-in keys, and build the alignment-pin receptacles.

Quality and inspection teams use it to check chamber dimensions, verify fit, and confirm that the intended keying actually blocks the wrong unit. It is relevant in electronic equipment systems built around the 482,6 mm (19 in) subrack format, especially where printed board type plug-in units are involved.

What changed in kSIST FprEN IEC 60297-3-103:2026 from the previous edition?

This second edition cancels and replaces the first edition published in 2004. The foreword says it is a technical revision.

The listed technical changes are:

• It was created based on the technological schemes of the full modular structure of the 19 in standards series, clarified by IEC TR 60297-3-1:2023.
• All figures were improved so that the interface dimensions and definitions are clearer for users.

Which standards are used with kSIST FprEN IEC 60297-3-103:2026?

• IEC 60297-3-101 - Provides the base dimensions for subracks and associated plug-in units, and supplies the related dimensions that this part refers to when values are bracketed or omitted.
• IEC 60297-3-102 - Covers the injector/extractor handle, and this part may be used together with it.
• IEC 60917-1:2019 - Provides the terms and definitions used for the purposes of this document.
• IEC TR 60297-3-1:2023 - Cited in the foreword as the reference that clarifies the modular structure of the conventional 19-inch subrack system.

What does the kSIST FprEN IEC 60297-3-103:2026 document contain?

This document contains a foreword, an introduction, seven clauses, one table and thirteen figures. The figures cover the conventional 19-inch subrack structure, keying of plug-in units, subrack and plug-in unit interface dimensions, key dimensions, key programming, inspection dimensions, alignment and/or electrical contact arrangements, and the 2,54 mm offset guide-rail arrangement.

Table 1 gives the inspection dimensions for keying chambers, and clause 7 explains the dimensions used in the figures. In practice, the document is a drawing-and-dimension reference for design, manufacturing and inspection of compatible subrack interfaces.

SLOVENSKI STANDARD
oSIST prEN IEC 60297-3-103:2026
01-januar-2026
Mehanske konstrukcije elektronske opreme - Mere mehanskih konstrukcij v seriji
482,6 mm (19 in) - 3-103. del: Kodirni in poravnalni trn
Mechanical structures for electronic equipment - Dimensions of mechanical structures of
the 482,6 mm (19 in) series - Part 3-103: Keying and alignment pin
Bauweisen für elektronische Einrichtungen - Maße der 482,6-mm-(19-in-)Bauweise - Teil
3-103: Kodierung und Führungsstift
Structures mécaniques pour équipements électroniques - Dimensions des structures
mécaniques de la série 482,6 mm (19 pouces) - Partie 3-103: Codage et broche
d'alignement
Ta slovenski standard je istoveten z: prEN IEC 60297-3-103:2025
ICS:
31.240 Mehanske konstrukcije za Mechanical structures for
elektronsko opremo electronic equipment
oSIST prEN IEC 60297-3-103:2026 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN IEC 60297-3-103:2026

oSIST prEN IEC 60297-3-103:2026
48D/795/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60297-3-103 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2025-11-14 2026-02-06
SUPERSEDES DOCUMENTS:
48D/791/RR
IEC SC 48D : MECHANICAL STRUCTURES FOR ELECTRICAL AND ELECTRONIC EQUIPMENT
SECRETARIAT: SECRETARY:
Germany Mr Arno Bergmann
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

SC 48B
ASPECTS CONCERNED:
Safety
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of
which they are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some
Countries” clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is
the final stage for submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Mechanical structures for electronic equipment - Dimensions of mechanical structures of the
482,6 mm (19 in) series - Part 3-103: Keying and alignment pin

PROPOSED STABILITY DATE: 2029
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

oSIST prEN IEC 60297-3-103:2026
IEC 60297-3-103 ED2 © IEC 2025

Link to Committee Draft for Vote (CDV) online document:
https://osd.iec.ch/#/editor/archive/3877bc98-42bb-df99-e063-b912000a38e2/en/CCDV/1

How to access
This link leads you to the Online Standards Development (OSD) platform for National Mirror
Committee’s (NMC) comments. The project draft may be found further down this document.

Resource materials
We recommend NCs to review the available materials to better understand the member commenting
on the OSD platform. This includes the:
• OSD NC roles overview
• How to add and submit comments to the IEC

Contact
Should you require any assistance, please contact the IEC IT Helpdesk.

oSIST prEN IEC 60297-3-103:2026
IEC 60297-3-103 ED2 © IEC 2025

CONTENTS
CONTENTS . 1
FOREWORD . 3
INTRODUCTION . 5
1 Scope and object . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Arrangement overview: Keying of plug-in units in a subrack. 6
4.1 General . 6
4.2 Subrack interface dimensions for keying . 8
4.3 Plug-in unit keying interface dimensions . 8
4.4 Key dimensions . 8
4.5 Programming of keys . 9
4.6 Keying chamber inspection dimensions . 10
5 Arrangement overview: alignment and/or electrical contact of a plug-in unit to a
subrack . 11
5.1 General . 11
5.2 Alignment and/or electrical contact receptacle in the subrack guide rail for
printed board type plug-in units (width dimension ≥ 4 × 5,08 mm) . 12
5.3 Alignment and/or electrical contact interface inspection dimensions . 13
6 Arrangement overview: Subrack guide rail and printed board, 2,54 mm offset of
the printed board reference plane . 13
6.1 General . 13
6.2 Dimensions of the subrack guide rail with 2,54 mm offset of the printed
board reference plane . 15
6.3 Reference plane for printed boards with 2,54 mm offset position . 16
7 Dimensions used in the figures . 16
Bibliography . 17

Figure 1 – Conventional 19-inch subrack system mechanical structure . 5
Figure 2 – Keying of plug-in unit in a subrack . 7
Figure 3 – Subrack interface dimensions for keying . 8
Figure 4 – Plug-in unit keying interface dimensions . 8
Figure 5 – Key dimensions . 9
Figure 6 – Programming of keys . 10
Figure 7 – Front and/or rear subrack and plug-in unit keying chamber inspection
dimensions . 10
Figure 8 – Alignment and/or electrical contact of a plug-in unit to a subrack . 11
Figure 9 – Alignment and/or electrical contact receptacle position in the subrack . 12
Figure 10 – Alignment and/or electrical contact interface inspection dimensions . 13
Figure 11 – Subrack guide rail and printed board, 2,54 mm offset of the printed board
reference plane . 14
Figure 12 – Dimensions of the subrack guide rail with 2,54 mm offset of the printed
board reference plane . 15
Figure 13 – Reference plane for printed boards with 2,54 mm offset position . 16

oSIST prEN IEC 60297-3-103:2026
IEC 60297-3-103 ED2 © IEC 2025

Table 1 – Subrack and plug-in unit keying chamber inspection dimensions . 10

oSIST prEN IEC 60297-3-103:2026
IEC 60297-3-103 ED2 © IEC 2025

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Mechanical structures for electronic equipment - Dimensions of
mechanical structures of the 482,6 mm (19 in) series -
Part 3-103: Keying and alignment pin

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 refe
...