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Private Integrated Services Network (PISN) - Inter-exchange signalling protocol - Call transfer supplementary service (QSIG-CT)

3rd edition, December 2001

This Standard specifies the signalling protocol for the support of the Call Transfer supplementary service (SS-CT) at the Q reference point between Private Integrated Network services eXchanges (PINXs) connected together within a Private Integrated Services Network (PISN).

SS-CT is a supplementary service which enables a User to transform two of that User’s calls (at least one of which must be answered) into a new call between the two other users in the two calls.

The Q reference point is defined in ECMA-133.

Service specifications are produced in three stages and according to the method specified in ETS 300 387. This Standard contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and stage 2 specifications in ECMA-177.

The signalling protocol for SS-CT operates on top of the signalling protocol for basic circuit switched call control, as specified in ECMA-143, and uses certain aspects of the generic procedures for the control of supplementary services specified in ECMA-165.

This Standard also specifies additional signalling protocol requirements for the support of interactions at the Q reference point between Call Transfer and other supplementary services and ANFs.

This Standard is applicable to PINXs which can interconnect to form a PISN.

The protocol defined in this Standard forms part of the PSS1 protocol (informally known as QSIG).

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CategoryData communication – PISN


Technical CommitteeTC32

ISO/IEC number13869

ETSI numberETS 300 261


  • ECMA-178, 1st editionNo file available
  • ECMA-178, 2nd edition, September 1997Download