Polycom C16 - Manual (Page 293)

Advanced Applications
9 - 77
set mute “Mics” 0
The in-room volume for the remote audio may be increased with the fader
command on the phone or video codec audio as follows.
inc fader “VSX8000 In” 1
inc fader “Phone In” 1
to increase the gain on the faders - making the “VSX8000 In” and “Phone In”
channels louder in the local room.