
FAA20 Embedded NEXCOM Vocoder
Board Manual
This manual has been prepared for the Federal Aviation Administration.
FA100-00107 (March 2004) – Rev 1.0.0 Page 27
Figure 13: Low Pass Filter Characteristics
5.3.6 Gain, Attenuation, Mute (GAM)
The gain, attenuation, and mute (GAM) block supports a signal adjustment
range of -36 dB to +21 dB for audio signals. Unlike the mixer, the GAM
block supports entries in Q4.12 format; thus, a setting of 0x1000
represents unity gain.
A calibration GAM block is provided to adjust for gain variations in the
analog front end. The calibration settings are programmed at the factory
and are stored in protected boot flash.
5.3.7 Voice Activity/Peak Detectors
The voice activity and peak level detectors are used to light FAA20 voice
activity indicators. There are activity and peak detectors place on all ports
of the mixer. The programmable LEDs can be configured to display any
one of the detectors (see Section 5.4.3). The activity and peak digital
thresholds are set at 0x0200 and 0x7FF0, respectively.
5 dB/division
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