[Freeswitch-users] Is it possible to access into an active call by admin?

Hey all, I got a new mission about monitor the call. We want to access into a certain call and got the video/audio from both 2 legs without be spotted by caller. Firstly I considered to transmit bridge to conference to support 3-way calling, but caller would turn into telephone view immediately after enter the conference room, without waiting callee accept the phone. Is there any solution for the conference or any suggestion for this function? Regards.