SSH EN 300 392-12-20 V1.2.1:2012

Terrestrial Trunked Radio (TETRA);Voice plus Data (V+D);Part 12: Supplementary services stage 3;Sub-part 20: Discreet Listening (DL)

Scope

This European Telecommunication Standard (EN) specifies the stage 3 description of the Supplementary Service Discreet Listening (SS-DL) for the Terrestrial Trunked Radio (TETRA). The DL supplementary service enables an authorized user to listen to one or more communications between TETRA subscribers Mobile Station (MS) without any indication to any user that the communication is being monitored. As options, the authorized user is able to intrude into the existing call and is able to forcefully clear the monitored call without call owner consent (in the case of a group call). Man-Machine Interface (MMI) and charging principles are outside the scope of the present document. The supplementary service stage 3 description is preceded by the stage 1 and the stage 2 description of the service, according to the method described in ITU-T Recommendation I.130 [i.2]. The stage 1 description specifies the service from the user's point of view. The stage 2 description identifies the functional capabilities of SS-DL and the information flows needed to support the supplementary service as specified in its stage 1 description. And the present stage 3 description specifies the protocols at the air interface and at the various Inter-System Interfaces (ISI) to support SS-DL.