scope:

This final draft European Telecommunication Standard (ETS) specifies the signalling protocol for the support of the Call Intrusion supplementary service (SS-CI) at the Q reference point between Private Telecommunication Network Exchanges (PTNXs) connected together within a Private Telecommunication Network (PTN).

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

The Q reference point is defined in ISO/IEC 11579-1.

Service specifications are produced in three stages and according to the method specified in ETS 300 387. This ETS contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and stage 2 specifications in ETS 300 425.

The signalling protocol for SS-CI operates on top of the signalling protocol for basic circuit switched call control, as specified in ETS 300 172, and uses certain aspects of the generic procedures for the control of supplementary services specified in ETS 300 239.

The impact on the protocol of interactions between the supplementary service specified in this ETS and other supplementary services is outside the scope of this ETS.

This ETS is applicable to PTNXs which can interconnect to form a PTN.