SIST-TP 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: 01-Sep-2026
• ICS: 35.240.60 - IT applications in transport
• ICS: 45.020 - Railway engineering in general
• Technical Committee: ŽEN - Electrical applications for railways
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 11-Jun-2026
• Due Date: 16-Aug-2026
• Completion Date: 02-Sep-2026
• Ref Project: CLC/TR 50542-3:2026 - Railway applications - Driver's cab Train Display Controller (TDC) - Part 3: Other Train Systems FIS

• Replaces: SIST-TP CLC/TR 50542-3:2017 - Railway applications - Driver's cab train Display Controller (TDC) - Part 3: Other train systems FIS
• Effective Date: 01-Oct-2026

SIST-TP CLC/TR 50542-3:2026 is the Slovenian adoption of CLC/TR 50542-3:2026, a CENELEC Technical Report for railway applications. It defines the functional interface between the Train Display Controller (TDC) in the driver’s cab and Other Train Systems (OTS), so engineers can see which data and functions pass between them.

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

SIST-TP CLC/TR 50542-3:2026 specifies the functional interface between the TDC and OTS. It focuses on exchanged data and functions, not on the physical devices themselves or on the conversion of physical signals into numerical form.

The scope excludes the display interface covered by CLC/TR 50542-2, ETCS/STM onboard as covered by Subset 121, and already designed class B ATP systems. The document is organized into Scope, Normative references, Terms and definitions, Symbols and abbreviations, General principles, Functions, an informative annex, and a bibliography.

Annex	What it covers
A	Examples of OTS functions and how they use the interface

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

SIST-TP CLC/TR 50542-3:2026 sets out how the TDC and OTS exchange information so that systems can be replaced, updated, or maintained with less interface redesign. In practice, this helps integrators keep the cab system stable while changing a subsystem such as brakes, HVAC, traction, or CCTV.

Interface boundary and purpose

The report defines the interface only at the functional level. That means project teams should use it to agree what information moves between systems, not how a specific controller is built or wired.

It also states that ETCS-related data are out of scope for this FIS. This keeps the interface aligned with the railway control and signalling specifications used elsewhere.

Main function groups

• State - OTS sends state information to the TDC. This is the main path for status-type information, including optional safety-related information, and the TDC then passes the processed result to the relevant display(s).
• Command - The TDC sends a request to an OTS. The request may come from a display, from the TDC itself, or from another interface connected to the TDC, such as ETCS/STM onboard or maintenance systems.
• Provide Video - OTS provides CCTV video to the TDC. This covers internal or external train video and is linked to the display system’s Show Video function.
• TDS Status - The TDC provides Train Display System (TDS) status to OTS. This is useful only where an OTS needs health or system-status information from the cab display system.
• OTS Status - If needed, OTS status is carried through the State function. The report treats this as part of the information exchange rather than a separate mechanism.

How the functions relate to CLC/TR 50542-2

The report includes a mapping between the display functions in CLC/TR 50542-2 and the functions here. For users, this is the key integration aid: it shows whether a display action is supported by OTS-to-TDC State data, by TDC-to-OTS Command, or by Provide Video.

Operating assumptions

The document does not define interface performance such as transmission speed or availability. It also makes clear that flashing is handled by the TDC, not by the OTS functions described here.

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

• Other Train System (OTS) - a train on-board system connected to the TDC, excluding displays, ETCS/STM onboard, and class B ATP systems.
• Train Display Controller (TDC) - the cab controller defined in CLC/TR 50542-1 that manages the dialogue with OTS.
• Train Display System (TDS) - the display system whose status can be reported by the TDC.
• Functional Interface Specification (FIS) - the kind of interface description used in this report.
• Input - information flowing from OTS to the TDC.
• Output - information flowing from the TDC to OTS.
• Closed-Circuit Television (CCTV) - the video source that can be provided to the TDC.

Who uses SIST-TP CLC/TR 50542-3:2026?

SIST-TP CLC/TR 50542-3:2026 is used by rolling stock designers, cab system integrators, suppliers of onboard subsystems, and maintenance engineers. It is also relevant to refurbishment projects, where teams need a clear interface to replace or upgrade OTS without redesigning the whole cab system.

The document is useful when deciding how the TDC should handle brakes, doors, traction, HVAC, passenger alarms, CCTV, and similar onboard functions. It gives a common functional language for procurement, interface control, and system integration.

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

Compared with CLC/TR 50542-3:2016, this edition updates the technical report as follows:

• Clause 2 no longer contains normative references.
• Notes were added to term entries 3.2 and 3.3.
• TDS was added in Clause 4.
• Clause 5 now refers to Annex A.
• Clause 5.1 clarifies direction from both the OTS and TDC point of view.
• Clause 5.2 adds clarification on the use of the function.
• Clause 5.3 adds a note on the source of the request.
• Annex A clarifies CCTV application.
• Annex A adds an OTS onboard hot box detecting system as an example of a safety-related OTS.

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

The report points to related documents rather than building the interface on normative references. CLC/TR 50542-1 defines the TDC and its general architecture, which is the base for understanding the controller mentioned throughout this part. CLC/TR 50542-2 defines the display systems FIS and provides the matching functions for the display side of the interface. Subset 121 is cited for the DMI-EVC interface and for the ETCS/STM onboard context mentioned in the notes and bibliography.

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

The document contains a functional model of the TDC-OTS interface, including a figure that shows the interface boundary and a second figure that defines input and output directions. It also includes a table that maps functions in CLC/TR 50542-2 to the corresponding functions in this report.

Annex A gives worked examples of OTS functions such as brake status, door opening, CCTV video, passenger alarm, and onboard hot box detection. Those examples help users apply the interface to real train subsystems without turning the report into a procurement specification.

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.
...