From Balise to Voice Group Call Service -
An Experts' Glossary of GSM-R Related Terms


Read more on a short history and brief technical overview of GSM-R

An Experts' Glossary of GSM-R terms


A device installed on the railway track in order to communicate with trains passing by. A balise can be either active or passive.

Broadcast call

In GSM-R, groups can be defined within a certain geographical area to which calls can be placed. The person who started the call can talk; other members of the group can only listen.

Cab radio

The radio and associated user interface within the cab of a locomotive. The cab radio is principally used by the locomotive driver.

Direct mode

Direct mode, in the context of GSM-R, refers to set-to-set or back-to-back cellular radio communications in which no use is made of any infrastructure on the ground.

Driver safety device

A driver safety device is mounted in the train and monitors the alertness of the driver. In case of doubt of the alertness of the driver, the device sends out a warning signal to other systems in the GSM-R network.

Functional numbering

Functional numbering or functional addressing describes the process of placing a call using a number that refers to the function which a user is performing at a certain time, as opposed to simply identifying the terminal equipment used. For example: rather than to Mr. Jones, a call is placed to the Chief Conductor of a specific train.

Functional identity

The description of the function performed by a person called or placing a call, whereby the user is identified by function (role) and not by the specific radio equipment or subscription used. See also: functional numbering.

General purpose radio

A GSM radio based closely on commercially available units, rather than on specific GSM-R equipment. As implied by the name, a general purpose radio is normally put in place for general use.


The process by which connection between a GSM-R based device and the GSM-R network is maintained, as the device moves from area to area. The communication channel control is passed from one base station to another, or between different channels within one cell.

Link assurance signal (LAS)

During critical maneuvers such as shunting, a link assurance signal is periodically or even constantly transmitted in one direction, from one radio to another, in order for the receiving user to detect a break in radio transmission.

Location dependent addressing

Addressing a particular function (such as a controller) based on the current location of the user (such as a specific train).


A number which identifies a unique subscription in a GSM-R network (or any other GSM-based cellular radio network).

Multi-party call

A group call in which a number of parties (defined by the initiator of the call) can participate. All parties may talk simultaneously at any one time.

Multiple driver communications

Communications between the drivers of each active cab in a train, comprising multiple traction vehicles.

Operational communications

Railway communications which are directly concerned with the movement or operation of the train.

Operational radio

A handheld radio which can be used by people involved in railway operations, such as shunting team members.

Primary controller

The primary controller is responsible for the operation of a designated area of track and is usually the coordinator of train emergency calls. A primary controller can be uniquely identified by the location and direction of a train.

Radio Block Centre

This ERTMS/ETCS describes centralized safety unit that is used to establish and control train separation.

REC (Railway Emergency Call)

A Railway Emergency Call in GSM-R is a VGCS group call with a high priority (level 0), used to inform drivers, controllers and other personnel of a level of danger requiring all train movement in a certain area to stop.


The use of a GSM-R (or any other GSM based device) on any network which is not the home network of the user.

Routing database

This database contains the relationships between a functional number and the MSISDN.

Secondary controller

A secondary controller holds responsibility for the safe operations of the trains on a designated area of the track. Secondary controllers require communications with trains in every possible situation. The split of responsibilities between primary controllers and secondary controllers differs between various railway organizations.

Shunting emergency call

A railway emergency call used to instruct shunting teams to cease their work immediately.

Shunting team

A group of people maneuvering trains in order to change their composition. Communications for shunting are particularly critical when a driver at the front of a train is pushing it backwards towards buffers or other potential obstructions. Often, a lookout will report progress to the driver.

Support communications

All railway communications which are not immediately concerned with train movements or operation. Support communications in a GSM-R context can involve the passage of catering, maintenance or information to the passenger.

Train control system (TCS)

The process by which the movement of a train is influenced without any action of the driver. This includes automatic train protection, automatic train operation and in-cab signaling. The European Train Control System (ETCS) is a signaling, control and train protection system which, in GSM-R, replaces many incompatible safety systems which were previously used in and around Europe, in particular on high-speed routes.

Train controller

The person who has the responsibility for the safe movement of trains.

VGCS (Voice Group Call Service)

A call made to all members of a group within a certain geographical area. Only one member of the group can talk at any time, while the other group members listen. Unlike a broadcast call, all users can participate in the call. But other than in a multi-party call, only one user can talk at any one time. By pressing or releasing the so-called PTT (Push-to-Talk) button, a listener can take the word, or a talker can become a listener.