This ETS contains the coding of information necessary for support of supplementary service operation on the mobile radio interface layer 3. Clause 2 gives the functional definitions and contents of messages for call independent supplementary service operations. Messages necessary for support of call related supplementary service operations are defined in TS GSM 04.08. Clause 3 gives the general format and coding for messages used for call independent supplementary service and the format and coding of information elements used for both call related and call independent supplementary service operations. Clause 4 gives the specification of the call related and call independent supplementary service operations.