
Configuring WAN Line Services
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Setting the Line-Coding Method
T1 uses bipolar format for signals. In bipolar format, alternating positive and
negative pulses on the digital line signify the number 1, and the absence of a pulse
signifies 0 (see Figure 6-2). A long string of zeros causes the line to lose
synchronization due to lack of pulses. Nortel Networks provides a line-coding
mechanism to maintain synchronization.
Table 8-15
lists the line coding options.
Using Site Manager
See the Line Coding parameter on page A-45 for information.
Table 8-15. FT1 Line Coding Options
Option Description
B8ZS The default; bipolar with 8 zero substitution (B8ZS) line coding replaces
a block of eight consecutive binary zeros with an 8-bit B8ZS code.
For more information on B8ZS line coding, see “Enabling or Disabling
Bipolar with 8 Zero Substitution (B8ZS)” on page 6-5.
AMI AMI line coding is also bipolar: a binary 0 is transmitted as zero volts,
and a binary 1 is transmitted as either a positive or negative pulse,
opposite in polarity to the previous pulse. (When configured for AMI line
coding, the FT1 link module remains synchronized upon receiving up to
45 consecutive zeros.)
Note:
If the T1 receive path detects a B8ZS code word when the line is
configured for AMI coding, the router generates a log message and an SNMP
trap.
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