Polycom SoundStructure C16 Design Manual page 450

Design Guide for the Polycom SoundStructure C16, C12, C8, and SR12
To ensure the wireless microphone will be the active microphone if the pre-
senter with the wireless microphone is picked up by another nearby
microphone, the automixer channel bias for the wireless microphone will be
set to 6dB as shown in the following figure.
Finally, it is necessary to review the AEC reference for the different micro-
phones to ensure that acoustic echoes are cancelled in the system.
The AEC reference for the wireless microphone should include the lectern
microphone (as that will be reinforced into the room) and any remote audio
sources - the phone line in this case, and the program audio material.
13 - 58