[Freeswitch-dev] how to link two audio conference in freeswitch?

hi guys, i just want to know how to do that in freeswitch. for example, i have two audio conference 3001 and 3002, which has it's own members in conference ,and now i want all user in the two conference can hear all the talking. first it may think transfer the member of 3001 to 3002, but it is not want i want, cause if i may link any two conference, and when i cancel such link, the member in the original conferece was not affected. thanks for any clue in advance. dbsk