Polycom SoundStructure C16 Design Manual page 124

Priority
The microphone priority parameter can be used with gated automixer groups to provide a priority of which
microphones to keep gated on when the NOM limit is reached and can also provide a 'soft chairman'
functionality by prioritizing which microphones can be gated on. Microphones with priority 1 are the highest
priority, microphones with priority 4 are the lowest priority.
If there is a group NOM limit, the priority parameter helps determine which microphones are allowed to gate
on. If the NOM limit is reached, a new high priority microphone turns off a lower priority microphone to make
room for itself (if a lower priority microphone is currently on). If all of the open microphones have the same
priority, they operate on a first come, first served basis. In addition to the NOM limit sequencing, some
attenuation may be applied to lower priority microphones when a higher priority microphone becomes
active.
Chairman Mic
The chairman mic feature allows the activation of microphones of important talkers to suppress activation
of other microphones. Each microphone may be individually configured as chairman or non-chairman.
Multiple microphones in the same group may be configured as chairman mics. If a chairman mic is
activated, all non-chairman mics in its automixer group is off-attenuated. Other chairman mics, however,
would still be allowed to activate.
Last Mic Mode
When using the gated automixer, last mic on mode can be selected individually for each virtual channel.
Depending on which channels have last mic on enabled, the behavior may differ. Last mic on mode is
ignored when using the gain sharing mixer.
● If no microphones have last mic mode enabled, all of the channels gate off when no channels are
active
● If all of the microphones have last mic mode enabled, the last mic to have any activity is always gated
on.
● If only one microphone has last mic mode enabled, this microphone turns on when no other
microphones are active. An example of this could be with an instructor's microphone.
● If some microphones have last mic mode on and some do not, then the behavior varies depending
on whether the last active microphone has last mic mode on. If so, that microphone is enabled, if not,
then the first microphone in the group with last mic mode on is enabled.
Gain Sharing Automixer Parameters
Slope
The Slope parameter determines the selectivity of how the gain is adjusted on the gain-sharing automixer
by setting a multiplier on the gain that is applied to active microphones. The difference in levels detected by
the automatic microphone on the active microphones are scaled by the slope parameter to create a gain for
the automixer. For systems with large numbers of microphones, increasing the slope biases the system to
provide gain to the more active microphones. The default value is 2.
Channel Bias
The channel bias control allows the automixer to be biased towards (positive bias value) or against
(negative bias value) activating a particular microphone more so than other microphones. When the channel
bias is positive, the signal that the automixer sees is made louder by the gating bias value than it really is,
even though the actual signal level is unchanged.
Polycom, Inc. 124