Revolabs Fusion Microphone System — Polycom FX - Manual (Page 4)

5. Verify that ECHO CANCELLATION is OFF
6. The Viewstation FX does not have a way to modify the input volume from the
Fusion. If additional volume is needed, activate the appropriate Fusion DIP switch to
increase the Fusion CONF OUT output level by 6dB
NOTE: You must use your Fusion remote control to control the room volume
for both the audio and video conference calls. Adjusting the volume in the
video codec will cause echo.