The present document specifies the stage 2 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 call and then subsequently, if desired, re-establish
communication.
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
ITU-T 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 EN 300 392-10-12 [7]).
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.