When talking about ERTMS, we presently talk about two systems (i.e. ETCS and GSM-R):

• ETCS (European Train Control System), a train control standard, based on onboard equipment able to supervise train movements at all times and to stop the train if it moves beyond the permitted stopping point. Information sent to the cab is received from the trackside equipment, Eurobalises or radio, depending on the operation level. The driver’s response is continuously monitored and, if necessary, ETCS takes control and activates the emergency brakes.
• GSM-R (Global System for Mobile Communications - Railways) is the European radio communications standard for railway operations. Based on GSM radio technology, GSM-R uses exclusive frequency bands for communications between the train and traffic control centres and the trackside devices (Radio Block Centres [RBCs]).

Therefore, ERTMS is a system contributing to interoperable railways throughout Europe. It allows a train equipped with an ERTMS onboard device produced by any supplier to run on track sections equipped with ERTMS devices made by other suppliers. This capability also implies the ability for any onboard equipment installed on any train to behave in the same way in the same circumstances.