First call: One of the subscriber A calls (answered).
Notification Indicator (NI):
Indicates to each remote party in which state of the other remote party ECT was performed (active, alerting).
Redirection Number (Rdn):
Includes the presentation indicator and the directory number of the other remote party.
The other subscriber A call (answered or alerting).
Subscriber A (PARTY A):
The served mobile subscriber - the one who has subscribed to, and invokes the ECT Supplementary Service.
Subscriber B (PARTY B):
The other party in the subscriber A first call.
Subscriber C (PARTY C):
The other party in the subscriber A second call.
Subscriber D (PARTY D):
The forwarded-to party when the call is forwarded by the subscriber C.
The resulting call after successful explicit call transfer between B and C.