a multi-party call, one timeslot is dedicated to each user. The second advantage compared to multi-party calls is that it is not necessary to know which mobiles are to take part in the call. A VGCS call is established on a purely geographic basis, subject to a mobile having previously enabled reception of the group concerned. VBS (Voice Broadcast Service) VBS is a broadcast group call: this means that compared to VGCS, only the initiator of the call can speak. The others who join the call can only be listeners. This kind of call is mainly used to broadcast recorded messages or to make announcements. REC (Railway Emergency Call) REC is a group call, or VGCS, dedicated to urgency. It is a higher priority call (REC priority is level 0 – see below : eMLPP). SEC (Shunting Emergency Call) The Shunting Emergency Call is a dedicated group call with the number 599. The call is established with an emergency level priority whose level is the highest possible priority 0. The SEC is enabled and used by devices registered for shunting operations. The establishment of such a call leads to automatic acceptance of the call on all enabled devices within the current area or cell-group configured. Multi-Level Precedence and Pre-emption Service (eMLPP) This defines the user's priority. The different priority levels are: A and B: Highest priority levels (not used by GSM-R networks) 0: Highest priority levels for ASCI and normal calls (mainly used for REC calls) 1: Lower priority than level 0 2: Lower priority than level 1 3: Lower priority than level 2 4: Lowest priority level (default priority, assigned to Point-to-Point calls) An Auto-Answering feature with a timer is also available for calls with priority 0, 1 and 2. GSM-R Numbering Plan The EIRENE SRS document defines a fixed numbering plan for GSM-R. It is defined by number prefixes. {| class="wikitable" ! Prefix ! Usage definition |- | 1 | Reserved for short codes |- | 2 | Train Function Number |- | 3 | Engine Function Number |- | 4 | Coach Number |- | 50 | Group calls |- | 51 | Broadcast calls |- | 52–55 | Reserved for international use |- | 56–57 | Reserved for national use |- | 58 | Reserved for system use |- | 59 | Reserved for system use |- | 6 | Maintenance and shunting team members |-