[asterisk-dev] Attended transfer: transferring a call as soon as the destination starts ringing

[Alex]

Hi all!

Ext A, B and C are SIP phones.

Ext A receives a call from Ext B. Ext A wants to transfer the call to
Ext C.  Ext A puts the first call on hold, dials Ext C, then simply
hangs up as soon as the call to Ext C starts *ringing*. In other
words, Ext A wants to be sure Ext C is ringing (i.e. it is not busy or
unavailable) but doesn't want to talk to him.

Unfortunately, as soon as Ext A hears Ext C is ringing and hangs up or
hits "Transfer", the call is closed and a *new* call from Ext B to Ext
C starts. This way, Ext C sees an unanswered call from Ext A, which is
an unexpected behaviour.

I played with directmedia and directrtpsetup, but no success so far.
Any ideas, please?

Thanks in advance.

Alex