
Configuring FE1 Services
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9-7
Setting the FE1 Line Coding
E1 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.
By default, the FE1 interface uses HDB3 line coding. You can select AMI line
coding instead.
AMI line coding is also bipolar: a binary 0 is transmitted as 0 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 FE1 link module
remains synchronized upon receiving up to 45 consecutive zeros.)
Table 9-4
lists the line coding options.
Table 9-4. FE1 Line Coding Options
BCC Option Site Manager Option Description
hdb3 HDB3 The default; the FE1 interface uses HDB3 line
coding. High-density bipolar coding (HDB3) is
a mechanism used to maintain sufficient ones
density in the E1 data stream.
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 E1 receive path detects a HDB3 code word when the line is
configured for AMI coding, the router generates a log message and an SNMP
trap.
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