scope:

The present document defines the stage 2 specifications of the Supplementary Service Priority Call (SS-PC) for the Terrestrial Trunked RAdio (TETRA). TheSS-PCisdefined to enableausertohavepreferentialaccessto thenetwork resourcesinaTETRAsystemin times of congestion. The SS-PC applies for the basic services: circuit mode calls (speech or data). 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 (SwMI), 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 extend over ISI to several TETRA systems.