The present document defines the stage 2 specifications of the Supplementary Service Call Authorized by Dispatcher (SS-CAD) for the Terrestrial Trunked Radio (TETRA) as provided by European operators. Stage 2 identifies the functional entities involved in the supplementary service and the information flows between them. Stage 2 is part of three stage definition where stage 1 (EN 300392-10-6 [1]) specifies the service description and the procedures of the supplementary service and stage 3 specifies the service primitives, PDUs and protocols for functional entities.