The present document specifies the stage 2 description of the Supplementary Service Area Selection (SS-AS) for the
Terrestrial Trunked Radio (TETRA).
SS-AS enables a user to select an area where a call will be set up.
Man-Machine Interface (MMI) and charging principles are outside of the scope of the present document.
Supplementary service specifications are produced in three stages according to the method defined in
CCITT Recommendation I.130 [1]. The stage 2 description identifies the functional capabilities and the information
flows needed to support the supplementary service as specified in its stage 1 description (see ETS 300 392-10-8 [8]).
The stage 2 description is followed by the stage 3 description, which specifies the protocols at the air interface and at
the various Inter-System Interfaces (ISI) to support the service.
The present document is applicable to TETRA Voice plus Data terminal equipment and networks.