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 i