This International Standard specifies the Supplementary Service (SS) Single Step Call Transfer (SSCT), which is applicable to various basic services supported by Private Integrated Services Networks (PISN). Basic services are specified in ISO/IEC 11574.

SS-SSCT is a supplementary service that enables an SSCT user, user A, to transform an existing call between user A and user B into a new call between user B and a user C whereby user A does not have a call established with user C prior to call transfer.

Supplementary service specifications are produced in three stages, according to the method described in ETS 300 387. This International Standard contains the stage 1 and stage 2 specifications of SS-SSCT. The stage 1 specification (clause 6) specifies the general feature principles and capabilities. The stage 2 specification (clause 7) identifies the Functional Entities involved in the supplementary service and the information flows between them.