scope:

This ETS defines the stage 2 specifications of the Supplementary Service Priority Call (SS-PC) for the Trans-European Trunked Radio (TETRA).

The SS-PC is defined to enable a user to have preferential access to the network resources in a TETRA system in times of congestion. The SS-PC specifies the definition, activation, deactivation and interrogation for the usage of low and high call priorities in the TETRA system. The SS-PC operations are defined for Switching and Management Infrastructure (SsMI), for the Mobile Station (MS) and for the Line Station (LS). SS-PC is defined for subscribers of one TETRA system, but the subscribers may be located in several TETRA systems and the information flows may be delivered over the Inter System Interface (ISI). SS-PC may also be invoked for basic services within one TETRA system or for basic services that extent over ISI to several TETRA systems.

The pre-emptive priorities, Man-Machine Interface (MMI) and charging principles are outside of the scope of this ETS.

Stage 2 describes the functional capabilities of the supplementary service introduced in stage 1 description. Stage 2 identifies the functional capabilities for the management and operation of the service in the SwMI, in the MS and in the LS. Stage 2 describes also the information flows exchanged between these entities and the flows sent over the ISI.

NOTE: The stage 2 description is followed by the stage 3 description, which specifies the encoding rules for the information flows and process behaviour for the different entities in the SwMI, the MS and LS.