A.4 Consultative call transfer with third party call control

24.6293GPPExplicit Communication Transfer (ECT) using IP Multimedia (IM) Core Network (CN) subsystemProtocol specificationRelease 18TS

An example of a call flow is given in figure E.5 of 3GPP TS 24.628 [10].

Annex B (informative):
Example of filter criteria