scope:

This European Telecommunication Standard (ETS) specifies the Call Intrusion supplementary service (SS-CI), which is applicable to basic services supported by Private Telecommunication Networks (PTNs). Basic services are specified in ETS 300 171.

Call Intrusion (SS-CI) is a supplementary service which, on request from the served user, enables the served user to establish communication with a busy called user (user B) by breaking into an established call between user B and a third user (user C).

Service specifications are produced in three stages, according to the method described in ETS 300 387. This ETS contains the stage 1 and stage 2 specifications of SS-CI. The stage 1 specification (clause 6) specifies the supplementary service as seen by users of PTNs. The stage 2 specification (clause 7) identifies the Functional Entities involved in the supplementary service and the information flows between them.

The purpose of the stage 1 and stage 2 specifications is to guide and constrain the work on signalling protocols at stage 3. Stage 3, the definition of the network and access layer 3 signalling protocols to support the supplementary service, is defined in separate standards.

NOTE 1

For this ETS, stage 2 does not consider the split of functionality between a functional TE at user B and the local PTNX. TE functions and local PTNX functions at user B are included in the same Functional Entity.