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APPENDIX D: G.703/G.704 Rear Card Module
Line Coding Options
High Density Bipolar 3 (HDB3): In HDB3 coding, the transmitter deliberately
inserts a bipolar violation when excessive zeros in the data stream are detected.
The receiver recognizes these special violations and decodes them as zeros. This
method enables the network to meet minimum pulse-density requirements. Use
HDB3 unless AMI is required in your application.
Alternate Mark Inversion (AMI): AMI coding does not inherently account for ones
density. To meet this requirement, you should make sure that the data inherently
meets pulse density requirements.
Switch S1-2: CRC-4 Multiframe
CRC-4 multiframe uses time slot zero to carry CRC-4 information. When CRC-4 is
enabled (ON), the unit synchronizes to the CRC-4 multiframe protocol.
Table D-2. CRC-4 multiframe.
S1-2
Option
Off
Disabled
On
Enabled
NOTE
When the data rate is set to 2048 kbps, the module transmits user data
on all 32 timeslots, ignoring framing information. In this case, switch
S1-2 will be ignored.
Switch S1-3: Clear Channel Mode
When S1-3 is in the Off position, the module is running in G.703 clear channel
mode. When S1-3 is in the On position, the module is running in G.704 framed
mode. When the module is set to framed mode, channel 0 will be used to pass
G.704 framing information that results in a maximum bandwidth of 1984 kbps for
user data.
Table D-3. Clear channel mode.
S1-3
Option
Off
Clear Channel Mode (G.703)
On
Framed Mode (G.704)