scope:

The present document specifies the stage 3 description of the Supplementary Service Call Hold (SS-HOLD) for the Terrestrial Trunked Radio (TETRA). SS-HOLD enables a user to interrupt communication on an existing individual call and then subsequently, if desired, re-establish communication. Man-Machine Interface (MMI) and charging principles are outside the scope of the present document. Supplementary service specifications are produced in three stages according to the method defined in ITU-T Recommendation I.130 [1]. The stage 1 description specifies the service from the user's point of view (see ETS 300 392-10-12 [7]). The stage 2 description identifies the functional capabilities and the information flows needed to support the service as specified in its stage 1 description (see EN 300 392-11-12 [8]). The present stage 3 description specifies the protocols at the air interface and at the various Inter-System Interfaces (ISI) to support SS-HOLD.