CAN/CSA-ISO/IEC 15051-01

Scope
 
This International Standard specifies supplementary service Recall (SS-RE), which is applicable to various basic services
supported by Private Integrated Services Networks (PISN). Basic services are specified in ISO/IEC 11574.
 
SS-RE is a supplementary service which provides for the redirection of a call transferred by the served user back to the served user if the call is unanswered. SS-RE is only applicable after transfer by join, not after transfer by rerouteing.
 
Service specifications are produced in three stages, according to the method described in CCITT Rec. I.130. This International
Standard contains the stage 1 and stage 2 specifications of SS- RE. The stage 1 specification (clause 6) specifies the supplementary service as seen by users of PISNs. The stage 2 specification (clause 7) identifies the functional entities involved in the supplementary service and the information flows between them.