CLC/TR 50542-3:2026

• Abstract:

  The scope of this document is the definition of the functional interface between the TDC and other train systems. These "Other Train Systems" are the train systems interfacing with the TDC excluding the displays (CLC/TR 50542-2), ETCS/STM onboard (Subset-121) and already designed class B ATP systems. The functional interface deals with data exchanged between the TDC and these train systems as shown in Figure 1. The TDC is defined in document CLC/TR 50542-1. (...)

• Status: Published
• Publication Date: 04-Jun-2026
• ICS: 35.240.60 - IT applications in transport
• ICS: 45.020 - Railway engineering in general
• Technical Committee: CLC/TC 9X - Electrical and electronic applications for railways
• Drafting Committee: CLC/TC 9X/WG 12 - Communication means between safety equipment and man machine interface (mmi)
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 05-Jun-2026
• Due Date: 17-Jul-2026
• Completion Date: 05-Jun-2026
• Ref Project: SIST-TP CLC/TR 50542-3:2026 - Railway applications - Driver's cab Train Display Controller (TDC) - Part 3: Other Train Systems FIS

• Replaces: CLC/TR 50542-3:2016 - Railway applications - Driver's cab train Display Controller (TDC) - Part 3: Other train systems FIS
• Effective Date: 10-Dec-2024

CLC/TR 50542-3:2026 is a CENELEC Technical Report for railway applications about the Train Display Controller (TDC) in the driver's cab and its interface with Other Train Systems (OTS). It specifies the functional interface and the data exchanged between the TDC and OTS, excluding display systems, ETCS/STM onboard and already designed class B ATP systems. It is meant for engineers, suppliers and maintainers who need a common functional description of TDC-connected train systems.

What does CLC/TR 50542-3:2026 specify?

CLC/TR 50542-3:2026 defines the functional interface between the TDC and OTS. In practice, it tells readers what information flows between these systems and how the functions are grouped.

The document is organized into:

• Clause 1, Scope
• Clause 2, Normative references
• Clause 3, Terms and definitions
• Clause 4, Symbols and abbreviations
• Clause 5, General principles
• Clause 6, Functions
• Annex A, informative examples of OTS functions

The scope excludes the display interface covered in Part 2, ETCS/STM onboard, and class B ATP systems. The TDC itself is defined in Part 1. The scope also notes that conversion of physical signals into numerical representation is outside the document's scope, so implementers still need separate engineering decisions for signal acquisition.

What are the key requirements of CLC/TR 50542-3:2026?

Functional boundaries and what is covered

CLC/TR 50542-3:2026 focuses on the functional interface, not on physical equipment architecture. Clause 5 says the TDC and OTS are treated by their functions, which helps teams define interfaces even when hardware changes.

Clause 5 also states that ETCS-related data are outside this FIS to avoid conflicts with TSI CCS specifications. For readers, that means this report is for non-ETCS OTS behavior and should not be used to define ETCS/STM onboard interfaces.

The document also says performance characteristics such as transmission speed and availability are not defined. In practice, those topics must be agreed separately by the project or subsystem specification.

How the functions are structured

Clause 6 gives a common template for each function: functional description, direction, parameter, feedback, safety related, and status. This is useful because it gives integrators a consistent way to describe each interface behavior.

Clause 6.2 defines State as information going from OTS to the TDC. Clause 6.3 defines Command as a request from the TDC to an OTS. Clause 6.4 defines Provide Video for CCTV from OTS to the TDC, and Clause 6.5 defines TDS Status from the TDC to OTS. Practically, this lets engineers assign each exchanged message to a clear functional role.

Relationship to the display part and to real train functions

Clause 6.6 maps functions in CLC/TR 50542-2:2025 to the functions in this document. The mapping shows, for example, that display-related outputs in Part 2 are handled here mainly as State, while display-related inputs map to Command. That matters when a supplier has to connect one OTS function to a cab display function without mixing the two parts.

Annex A gives examples such as brake status, door opening request, CCTV video, passenger alarm and onboard hot box detection. These examples help readers see how the interface works on actual train systems and where safety-related behavior may apply.

What terms does CLC/TR 50542-3:2026 define?

• Other train system (OTS) - a train onboard system that interfaces with the TDC, excluding ETCS/STM onboard, class B ATP systems and displays.
• Train Display Controller (TDC) - the controller in the driver's cab that manages the interface with other train systems.
• Train Display System (TDS) - the display system associated with the TDC.
• input - information going from the OTS to the TDC.
• output - information going from the TDC to the OTS.
• Functional Interface Specification (FIS) - the functional description of the interface behavior between systems.
• Command - a TDC request sent to an OTS.
• State - information sent from an OTS to the TDC.

Who uses CLC/TR 50542-3:2026?

CLC/TR 50542-3:2026 is used by rolling stock designers, cab refurbishment teams, subsystem suppliers and maintenance engineers. It is especially relevant in new rolling stock development and driver's cab refurbishment, where several suppliers may need a shared interface definition.

It also supports maintenance and replacement work. By defining the function at the interface level, the report helps teams exchange or update an OTS or a TDC without redesigning the whole cab system.

What changed in CLC/TR 50542-3:2026 from the previous edition?

CLC/TR 50542-3:2026 supersedes CLC/TR 50542-3:2016. The foreword lists these changes:

• Clause 2 was updated and the normative references were deleted.
• A note was added to term entry 3.2.
• A note was added to term entry 3.3.
• TDS was added in Clause 4.
• Clause 5 now refers to Annex A.
• Clause 5.1 now describes direction clearly from the OTS and TDC point of view.
• Clause 5.2 adds clarification about use of the function.
• Clause 5.3 adds a note about the source of the request.
• Annex A clarifies CCTV application and adds an onboard hot box detecting system as an example of a safety-related OTS.

Which standards are used with CLC/TR 50542-3:2026?

The bibliography points to CLC/TR 50542-1, CLC/TR 50542-2 and Subset 121 as companion references.

• CLC/TR 50542-1 gives the general architecture of the TDC.
• CLC/TR 50542-2 defines the display systems FIS that this part maps to and from.
• Subset 121 is referenced for the DMI-EVC interface and the ETCS/STM onboard context.

These references provide the wider interface context, while CLC/TR 50542-3:2026 focuses on the OTS side of the TDC interface.

What does the CLC/TR 50542-3:2026 document contain?

The document contains two functional figures, one for the TDC-OTS interface and one for the definition of functional input and output. It also contains a function list in Clause 6 that explains State, Command, Provide Video and TDS Status.

Clause 6.6 includes a relationship table between Part 2 functions and the functions in this part. That table is useful when designing or checking message flows between cab displays and other train systems.

Annex A gives worked examples of OTS functions for design and integration work. The examples help readers relate the abstract interface definitions to brake systems, doors, CCTV and passenger alarm behavior.

SLOVENSKI STANDARD
01-oktober-2026
Nadomešča:
SIST-TP CLC/TR 50542-3:2017
Železniške naprave - Krmilnik vlakovnega prikazovalnika (TDC) v strojevodskem
prostoru - 3. del: Drugi vlakovni sistemi (FIS)
Railway applications - Driver's cab Train Display Controller (TDC) - Part 3: Other Train
Systems FIS
Bahnanwendungen - Display-Steuereinheit (TDC) für Führerräume - Teil 3: Andere
Zugsysteme FIS
Applications ferroviaires - Contrôleur d'écrans de cabine (TDC) - FIS pour autres
systèmes de train
Ta slovenski standard je istoveten z: CLC/TR 50542-3:2026
ICS:
35.240.60 Uporabniške rešitve IT v IT applications in transport
prometu
45.020 Železniška tehnika na Railway engineering in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT CLC/TR 50542-3

RAPPORT TECHNIQUE
TECHNISCHER REPORT June 2026
ICS 35.240.60; 45.020 Supersedes CLC/TR 50542-3:2016
English Version
Railway applications - Driver's cab Train Display Controller
(TDC) - Part 3: Other Train Systems FIS
Applications ferroviaires - Contrôleur d'écrans de cabine Bahnanwendungen - Display-Steuereinheit für Führerräume
(TDC) - FIS pour autres systèmes de train (TDC) - Teil 3: Andere Zugsysteme FIS

This Technical Report was approved by CENELEC on 2026-05-18.

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

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. CLC/TR 50542-3:2026 E

Contents Page
European foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
4 Symbols and abbreviations .6
5 General principles.6
6 Functions .7
6.1 General .7
6.2 State .7
6.3 Command .7
6.4 Provide Video .8
6.5 Management functions .8
6.5.1 TDS Status .8
6.5.2 OTS Status .8
6.6 Relationship between CLC/TR 50542-2:2025 and this document .8
Annex A (informative) Examples of OTS functions . 10
Bibliography . 11
European foreword
This document (CLC/TR 50542-3:2026) has been prepared by CLC/TC 9X “Electrical and electronic
applications for railways”.
This document supersedes CLC/TR 50542-3:2016.
3:2016:
— Clause 2: the normative references have been deleted.
— Note 1 added to term entry 3.2.
— Note 1 added to term entry 3.3.
— Clause 4: TDS added.
— Clause 5: addition of a reference to Annex A.
— 5.1: direction is clearly described from the OTS and TDC point of view.
— 5.2: clarification added about the use of the function.
— 5.3: a note has been added to clarify the source of the request.
— Annex A:
— application to CCTV has been clarified,
— OTS Onboard hot box detecting system added, as an example of safety related OTS.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A complete
listing of these bodies can be found on the CENELEC website.
Introduction
The extent of CLC/TR 50542-3 is the functional interface between the Other Train Systems (OTS) and the TDC.
The functional definition of this interface is a key feature in the process to increase market development, for
instance:
— by introducing more suppliers for new rolling stock development and for driver's cab refurbishment;
— by easing the control of maintenance and the replacement processes;
— by decreasing the related equipment Life cycle cost.
In this document, the train borne systems and the TDC are considered only regarding their functionalities and
not as physical devices.
The CLC/TR 50542 series consists of three documents:
— CLC/TR 50542-1, Railway applications — Driver's cab Train Display Controller (TDC) — Part 1: General
architecture;
— CLC/TR 50542-2, Railway applications — Driver's cab Train Display Controller (TDC) — Part 2: Display
systems FIS;
— CLC/TR 50542-3, Railway applications — Driver's cab Train Display Controller (TDC) — Part 3: Other train
systems FIS (this document).
This series of documents is not a standard but the result of a study on the future view of the system. They do
not describe an existing solution for the TDS.
These documents are not written to be used in call for tenders because they are not sufficient. However, they
can serve as a basis for future development and standardization including new technologies. These documents
are a first step and may be completed later.
NOTE In case of existing discrepancies between CLC/TR 50542-1:2025 and CLC/TR 50542-3:2026, the present
document prevails.
1 Scope
The scope of this document is the definition of the functional interface between the TDC and other train systems.
These “Other Train Systems” are the train systems interfacing with the TDC excluding the displays
(CLC/TR 50542-2), ETCS/STM onboard (Subset-121) and already designed class B ATP systems.
The functional interface deals with data exchanged between the TDC and these train systems as shown in
Figure 1.
The TDC is defined in document CLC/TR 50542-1.
...