BT8110 데이터 시트보기 (PDF) - Conexant Systems
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BT8110 Datasheet PDF : 84 Pages
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D
Appendix D. T1 ADPCM Transcoder
D.1.1 Description
D.1 Introduction
This appendix describes an assembly of the Bt8110/B ADPCM Processor,
Bt8200 ADPCM Line Formatter, and Bt8300 (dual), Bt8360 (single) T1
Clear-Channel Framers, or the Bt8370 T1/E1 Framer/LIU that realizes a
single-board transcoder meeting the interface requirements given in ANSI
Standard T1.302-1989. An evaluation board is available for this configuration
(Bt8200EVM–T1).
T1.302-1989 is a line format standard for 32 kbit/s ADPCM compression of
voice-band signals. It specifies three signaling methods for transcoders:
• Bundle Format—Provides 44 voice-band channels in a T1 along with four
signaling and alarm overhead channels.
• Transition Signaling—Provides 48 channels with 32 kbit/s ADPCM and
allows the switching of ADPCM in DS0s in DCS systems and network
managers and is thus compatible with fractional T1 services.
• Robbed-Bit Signaling—Provides 48 channels with 32 kbit/s and with
24 kbit/s used every sixth frame to provide bandwidth for signaling bits.
T1.303-1989/G.726 specifies the 24-kbit/s ADPCM algorithm used for
signaling frames.
A transcoder meeting the requirements of these standards and providing the
option of all three methods of signaling can be developed with three Conexant
products: Bt8110/B, Bt8200, Bt8300 (or Bt8360 or Bt8370 in place of Bt8300).
Two Bt8110/Bs provide transcoding for 48 channels; the code rate can be adjusted
from 32 kbit/s to 24 kbit/s on a channel-by-channel, frame-by-frame basis. The
Bt8200 buffers and synchronizes the transcoded PCM and ADPCM signals to
obtain the required line formats and translates the signaling bits as required.
Three T1 framers are used. Two T1 framers synchronize the X and Y (PCM) T1
ports; a third T1 framer provides frame synchronization and frame generation for
the Z interface that carries the compressed voice channels at 32 kbit/s.
100060C
Conexant
D-1
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