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Private Integrated Services Network (PISN) - Specification, functional model and information flows - Call offer supplementary service (COSD)

2nd edition, June 1997

This Standard specifies the Call Offer supplementary service (SS-CO), which is applicable to various basic services supported by Private Integrated Services Networks (PISN). Basic services are specified in ECMA-142.

Call Offer (SS-CO) is a supplementary service which, on request from the calling user (or on that user’s behalf), enables a call to be offered to a busy called user and to wait for that called user to accept this call.

Supplementary service specifications are produced in three stages, according to the method described in ETS 300 387. This Standard contains the stage 1 and stage 2 specifications of SS-CO. 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.

NOTE – For this Standard, stage 2 does not consider the split of functionality between a functional terminal and the local PINX. Terminal functions and local PINX functions are included in the same functional entity.

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CategoryData communication – PISN


Technical CommitteeTC32

ISO/IEC number14841

ETSI numberEN 300 361


  • ECMA-191, 1st edition, June 1993Download