scope:

In this European Telecommunication Standard (ETS) the general aspects of the specification of supplementary services at the layer 3 radio interface are given. GSM 04.8x and 04.9x-series specify the procedures used at the radio interface (reference point Um as defined in GSM 04.02) for normal operation, registration, erasure, activation, deactivation, invocation and interrogation of supplementary services. Provision and withdrawal of supplementary services is an administrative matter between the mobile subscriber and the service provider and cause no signalling on the radio interface.