TANDBERG Maestro MXP - Manual (Page 49)

Administrator Settings
49
Telephone
This indicates that there is a telephone participant in the conference. The
displayed number indicates how many telephone participants there are in the
conference.
Duo Video / H.239
This indicates that there is a Dual Video Stream sent from you (near end). The
feature Duo Video / H239 allows participants at the far end to simultaneously
watch a presenter on one screen and a live presentation on the adjoining screen.