Digital Voice Systems VC-20-ATC-10B, Руководство пользователя

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Section 6 – VC-20™ ATC-10b Vocoder Board Advanced Features
VC-20

ATC-10b Vocoder Board User’s Manual
page 10
The Speech Compression Specialists
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IGITAL
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OICE
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YSTEMS,
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GO The GO signal must be active to place the encoder in voice mode. This signal is sampled
every 20 ms when FMEN is high. If this signal is active then the encoder outputs voice
data on TXD during the next 20 ms frame. Otherwise, if this signal is inactive then the
encoder resets itself internally and outputs a silence frame on TXD during the next 20 ms
frame. The relationship between FMEN, GO and TXD is shown in Figure 1. If left
unconnected, GO is pulled to its active state (high).
TXD
Silence
Frames Voice
Frames
GO
FMEN
Voice
Frames Voice
Frames Silence
Frames
Figure 1: Voice/Silence Mode Selection
GND, AGND GND is the digital ground signal and AGND is the analog ground signal. These signals
are connected on the VC-20™ - ATC-10b.
3.5 Silence Frame Designation
The VC-20™ - ATC-10b encoder continually outputs a silence frame whenever the GO
signal is inactive (see Figure 1). If the decoder receives this signal it outputs a low level (-
75 dBm) noise signal on VFRO