use It is used to transmit data between trains and railway regulation centers with level 2 and 3 of ETCS. When the train passes over a Eurobalise, it transmits its new position and its speed, then it receives back agreement (or disagreement) to enter the next track and its new maximum speed. In addition, trackside signals become redundant. Other uses Like other GSM devices, GSM-R equipment can transmit data and voice. New GSM-R features for mobile communication are based on GSM, and are specified by EIRENE project. Call features are: PtP Call: Point-to-Point Call, the same type of call as a normal GSM call VGCS: Voice Group Call System, quite similar to walkie-talkie communication but with a single uplink handled by the network (only one person can speak at a time) VBS: Voice Broadcast System, like a VGCS but only the call initiator can speak (the other are only listeners) REC: Railways Emergency Call, is a special VGCS defined as 299 with the highest priority possible (0) SEC: Shunting Emergency Call, is a special VGCS defined as 599 with the highest priority possible (0) Priority control of all the different calls (PtP, VGCS, VBSm, REC and SEC calls) There are other additional features: Functional Addressing, alias system to call someone registered on the GSM-R network, only by knowing the temporary function user (engine driver of train such-and-such, ...) Location Dependent Addressing, routing system to call the most appropriate train controller regarding the current train position by dialling a pre-defined short code Shunting mode, when users work on the tracks. GSM-R features ASCI (Advanced Speech Call Items) features The following definitions are a part of the System Requirements Specification (SRS) as defined by the EIRENE standard. VGCS (Voice Group Call Service) VGCS allows a great number of users to participate in the same call. This feature imitates the analogue PMR (Private Mobile Radio) group call with the PTT key (Push-to-Talk). Three kinds of users are defined: the Talker, the Listener and the Dispatcher. The talker can become a listener by releasing the PTT key and a listener becomes a talker by pressing the PTT key. One advantage of VGCS compared to multi-party calls (the GSM conference call feature) is the spectrum efficiency. Indeed, when many users are in the same cell they will use only one frequency for all listeners and two frequencies for the talker (as in point-to-point call). In