The present document specifies the technical realisation of the handling of calls originated by a GSM mobile subscriber and calls directed to a GSM mobile subscriber, up to the point where the call is established. Normal release of the call after establishment is also specified.

The handling of DTMF signalling and Off-Air Call set-up (OACSU) are not described in the present document.

The details of the effects of GSM supplementary services on the handling of a call are described in the relevant GSM 03.7x, GSM 03.8x and GSM 03.9x series of specifications.

The specification of the handling of a request from the HLR for subscriber information is not part of basic call handling, but is required for both CAMEL (GSM 03.78 [8]) and optimal routeing (GSM 03.79 [10]). The use of the Provide Subscriber Information message flow is shown in GSM 03.78 [8] and GSM 03.79 [10].

The specification of the handling of data calls re-routed to a SIWFS is described in GSM 03.54 [4].

The logical separation of the MSC and VLR (shown in clauses 4, 5 and 7), and the messages transferred between them (described in clause 8) are the basis of a model used to define the externally visible behaviour of the MSC/VLR, which is a single physical entity. They do not impose any requirement except the definition of the externally visible behaviour.

If there is any conflict between this specification and the corresponding stage 3 specifications (GSM 04.08 [20], GSM 08.08 [22] and GSM 09.02 [23]), the stage 3 specification shall prevail.