The present document defines the stage 3 specifications of the Supplementary Service Late Entry (SS-LE) for the Terrestrial Trunked Radio (TETRA). SS-LE allows radio users to be informed of and, if they are concerned, to join an already existing point-to-multipoint speech or data call. Man-Machine Interface (MMI) and charging principles are outside the scope of the present document. Supplementary Service stage 3 specification is preceded by the stage 1 and the stage 2 specifications of the service. Stage 1 describes the functional capabilities from the user's point of view. Stage 2 defines the functional behaviour in terms of functional entities and informa