 it also includes high layer attributes (layers 4 to 7). The teleservice includes clear speech or encrypted speech in each of the following: Individual call (point-to-point) Group call (point-to-multipoint) Acknowledged group call Broadcast call (point-to-multipoint one way) A supplementary service modifies or supplements a bearer service or teleservice. PMR type supple- mentary services include: Access priority, preemptive priority, priority call Include call, transfer of control, late entry TETRA Network Planning Call authorised by despatcher, ambience listening, discreet listening Area selection Short number addressing Talking party identification Dynamic group number assignment Telephone type supplementary services include: List search call Call forwarding - unconditional/busy/no reply/not reachable Call barring - incoming/outgoing calls Call report Call waiting Call hold Calling/connected line identity presentation Calling/connected line identity restriction Call completion to busy subscriber/no reply Advice of charge Call retention D.3 TETRA Network Elements The TETRA standard describes the following network elements: Mobile station (MS) Switching and management infrastructure (SwMI) In practical implementations the SwMI is composed of the radio base stations and digital switching, but their internal structure and the interfaces between them are not standardised. Furthermore, the standard does not specify details about the dispatcher workstation, but it is considered as an external network user like PSTN or PABX. Figure D.2 shows the TETRA network elements and their connections in the most common applications. The network elements are: Radio terminal Radio base station Digital switch Dispatcher workstation The radio terminal is used by subscribers to get services from the network. Its main task is to guarantee the best possible service performance for the user. When the MS is switched on, cell selection and reselection processes allow it to be camped on the cell with the highest received power level. Differ