Yealink SIP-T4X Administrator's Manual page 461

The following figure illustrates successful 3-way calling between Yealink SIP-T4X IP
phones in which User A mixes two RTP channels and therefore establishes a conference
between User B and User C. In this call flow scenario, the end users are User A, User B,
and User C. They are all using Yealink SIP IP phones, which are connected via an IP
network.
The call flow scenario is as follows:
1. User A calls User B.
2. User B answers the call.
3. User A puts User B on hold.
4. User A calls User C.
5. User C answers the call.
Appendix
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