
Configuring WAN Line Services
8-8
308648-14.00 Rev 00
Setting the FT1 Line Coding
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 would cause the line to lose
synchronization due to lack of pulses. Nortel Networks provides a line-coding
mechanism to maintain synchronization.
Table 8-4
lists the line coding options.
Using the BCC
To set the line coding, navigate to the ft1 prompt (for example,
box
;
ft1/1/1
) and
type:
port-line-coding
variable
For example:
ft1/1/1#
port-line-coding ami
Table 8-4. FT1 Line Coding Options
BCC Option Site Manager Option Description
b8zs 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 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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