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Installation ~ LCD Programming
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Phantom Power
Each input will default with 24V phantom power enabled, but can be switched off to
accommodate input devices not requiring phantom power.
AGC
Each input can use automatic gain control (AGC). This feature keeps softer and
louder talkers at a consistent transmit level. This feature is disabled when shipped
from the factory. The target gain is 0dB. It adjusts at 2dB per second. The AGC
start adjustment is +20dB, but will adjust only +6dB. Adjustments will not be
made at .5dB either side of the target (0dB).
High-Pass Filter
A high-pass filter can be selected on each gated input to reduce unwanted noise. The
filter has a break frequency at 250Hz, suppresses the signal -3dB at 200Hz, then
rolls off at 6dB per octave. This feature is disabled when shipped from the factory.
EQ Status
A graphic equalizer can be enabled (on) or disabled (off) for each input. The
equalizer helps match characteristics of dissimilar microphones and adjust general
circuit tuning. This EQ circuit provides 12dB of cut or boost centered at frequencies
of 250Hz, 1kHz and 4kHz, Q factor of 1.4. This feature is disabled when shipped
from the factory. The levels of each band can be adjusted through the RS-232 port
with the MEQ command or in AP-Ware.
Chairman Mic
Each input can be selected as the chairman override microphone, allowing the
chairman’s microphone to gate on, regardless of which other microphones are on. As
shipped from the factory, this feature is disabled. This feature can have a single
microphone selected or a group of microphones selected.
Adaptive Ambient
The adaptive ambient mode can be turned on (default) and off. The recommended
setting is on. However, if the ambient noise in the room is constantly changing and
the AP400 is unable to track properly (see Figure 2.15), turn this mode off and set
the ambient level manually (see Manual Ambient, page 21). Fixed values range from
0dB to -70dB, with increments of 1dB.
Figure 2.15. Adaptive ambient