hi Ali,
this is how eavesdrop works, the arrow points to the direction of the audio flow, in this way C could listen but no talk:
C
^
|
|
A<----->o<----->B
this is how three_way works, C could listen and talk to A and B, just like in a conference:
C
^
|
|
v
A<----->o<----->B
Usage:
<action application="three_way" data="<uuid of a bridged call(A<->B)>"/>