Ilence Rame Esignation - Digital Voice Systems VC-20-ATC-10B User Manual

Section 6 – VC-20™ ATC-10b Vocoder Board Advanced Features
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
FMEN
GO
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
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Voice Silence Voice
Frames Frames Frames
Figure 1: Voice/Silence Mode Selection
D V
IGITAL OICE
The Speech Compression Specialists
Silence Voice
Frames Frames
VC-20 ATC-10b Vocoder Board User's Manual
S I
YSTEMS, NC.