The European Train Control System (ETCS) relies on precise and reliable trackside components to ensure safe and efficient railway operations. One of these components include:

Balises – a transponder placed between the rails on the railway track that communicates with onboard equipment on passing trains. Balises serve as data transmitters, providing essential information to trains for safe and efficient operations.

Key Features of a Balise 👀
Data Transmission: Balises transmit static data (e.g., location, track gradient, or speed restrictions) and dynamic data (e.g., signal aspects or temporary speed limits). This data is sent to the train’s onboard systems for processing.

Passive Operation: Most balises are passive; they are powered temporarily by the electromagnetic field generated by the passing train’s onboard antenna.

High Reliability: Balises are designed to function reliably in all weather conditions and can withstand heavy rail traffic.

Types of Balises 🚅
Fixed Balises:
Contain pre-programmed, unchanging information. Often used for location referencing or to indicate permanent speed restrictions.

Switchable Balises:
Linked to a Lineside Electronic Unit (LEU) and interlocking systems. Provide dynamic data, such as signal status or movement authority, based on track conditions.

Role in ETCS 🚅
Balises act as the “eyes” of the ETCS system, relaying precise location and operational data to trains. In ETCS Level 1, they are integral for transmitting trackside signal information, while in ETCS Levels 2 and 3, they support the Radio Block Centre (RBC) by confirming train positions.

Manufacturers of balises include Siemens Mobility, Alstom, Thales Group, Hitachi & CAF signalling.

Image credit: Network Rail Media Centre