The Speech Compression Specialists
D
IGITAL
V
OICE
S
YSTEMS,
I
NC.
1. Introduction
The Digital Voice Systems, Inc. (DVSI) VC-20™ - - voice codec is a full-duplex real-time voice
processing board. The VC-20™ - - contains proprietary software which implements the
Advanced Multi-Band Excitation™ (AMBE™) voice coding algorithm. DVSI grants a license
to its customers to use this software according to the terms established in the attached AMBE™
Software END USER License Agreement. Use of the VC-20™ - -, or any portion thereof,
signifies acceptance of these licensing terms.
The VC-20™ - - operates by digitizing an analog speech signal using an on-board A-to-D
converter. This digitized speech is then processed by the encoder and converted into a data bit
stream. This bit stream is output to a modem or similar device. Simultaneously, the VC-20™ - -
receives a data bit stream from a modem or similar device. This received bit stream is processed
by the decoder and converted into a synthetic speech signal which is then converted into an
analog signal using the on-board D-to-A converter. The encoder and decoder are fully
asynchronous.
The VC-20™ vocoder board is designed to use an Analog Devices AD28msp02 codec during
normal operation. This normal configuration can be modified so that the onboard codec is
disabled and the 16-bit linear digital interface can be used.
2. Operation
Connections are made to the VC-20™ Serial Speech Data Interface using signals on ROW B and
ROW C of the attached DIN 41612 connector which is described in Section 4. When using the
Serial speech data interface
the onboard codec MUST be disabled by installing a JUMPER
in Position 13 of JP1
.
VC-20--Connector Signals
Name
Direction
Description
SCLK
Input
Serial Port Shift Clock
DX
Output
Serial Speech Data Output (16–bit linear)
DR
Input
Serial Speech Data Input (16–bit linear)
FSX
Input
Data Output Framing Signal
FSR
Input
Data Input Framing Signal
SP_RDY
Output
Serial Port Ready Signal
VC-20
- Serial Speech Data Interface
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