Polycom EF2201 Brochure & Specs page 27

Microphone activation
There are two modes of microphone activation for an input that is assigned to one of the two automixers: auto gate, or forced-
on/forced-off. In auto gate mode, a microphone will gate on or off depending on the signal activity and the settings for that input
channel and for that mixer. This is the normal operating mode. If a channel is set to forced-on, the channel will operate as if it is
always gated on. This will affect the count of the number of open microphones which will affect the NOM attenuation that is
applied to any output signal that uses that input channel in its mix. If a microphone is forced-off, then the signal will never be
gated on and will always be attenuated by the amount of off attenuation.
Chairman Mode (On or Off). Any of the inputs to the automixers may be selected as a Chairman microphone. When the Chairman
microphone gates on, all the other microphones assigned to that mixer will be gated off. This allows the chairman to take
complete control of the meeting.
NOM Limit
The NOM limit feature allows the user to set the maximum number of microphones that may be automatically gated on for each
mixer (remember there are two independent automixers built into the Vortex). The actual maximum number of microphones that
will be on at any given time depends on the signal activity and whether any channels are forced-on. Forcing a microphone on will
override the NOM limit. For example, if NOM limit is set to 2 and there are two microphones that are presently gated on, if the
user forces a third microphone on, that third microphone will be forced on making the actual number of microphones gated on 3.
When the NOM attenuation is applied to an output that includes these three microphones in its mix, an attenuation of
=
10 log ( ) 3 . 4 77
dB will be applied to the output signal.
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Priority
There are four levels of gating priority associated with each microphone where priority 1 is the highest priority and priority 4 is the
lowest priority. This is a softer version of the Chairman Mode where higher priority microphones are allowed to displace lower
priority microphones. Here's how it works: the microphones with the higher priority are more important to the automixer when it
makes its gating decisions. For instance assume the NOM Limit is 2 (only 2 microphones are allowed to automatically gate on at
any given time) and a priority 1 microphone is gated and a priority 3 microphone is gated. If another priority 1 or priority 2
microphone is loud enough to gate the mixer then that microphone will be gated on and at the same time the priority 3 microphone
will be gated off because it is the lowest priority. In this example, because NOM Limit is set to 2, only 2 microphones can be
automatically gated on at one time.
In another example, if NOM Limit is 4 and two microphones with priority 1 are gating and two microphones with priority 2 are
gating, then a priority 3 or 4 microphone will have to wait until one of the priority 1 and 2 gated microphones gates off. Once that
happens the lower priority microphone can be gated (if there is enough signal activity to gate the microphone) and once gated it
will remain gated until a higher priority microphone gates on and takes priority – forcing the lower priority microphone to gate off.
Last Mic On Mode
Each automixer can be configured with Last Mic On mode in one of three ways. Last mic mode can be disabled, can be set to a
particular channel, or can be set to the last microphone that was gated on.
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