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positions. The first bit received for each DS0 byte is displayed in bit position 1
(least significant bit). If no channel is selected, the Data Bits LEDs will be off.
2-62. Signaling Bits LEDs
The signaling for the selected DS0 channel is dropped to the Signaling Bits
LEDs. These LEDs are labeled A, B, C, and D. The Signaling Bits LEDs will
be off if no channel is selected. Table 2-2, shown below, lists the signaling
bits.
Table 2-2. Signaling Bits Displayed Based on Framing and Signaling Type
Framing Detected
D4
ESF
SLC96
D4
ESF
ESF
None
2-63. Rx Status/History LEDs
The Rx Status LEDs provide a visual indication of an alarm condition. The
corresponding History LEDs provide a visual indication of the history of an
alarm condition.
2-64. AMI and B8ZS/HISTORY LEDs
Line coding is assumed to be AMI until a B8ZS substitution is detected. The
AMI and B8ZS LEDs automatically indicate the line coding present at the
receiver. However, in order to distinguish between AMI and B8ZS, the data at
the receiver must include at least one string that contains at least eight
consecutive zeros. If live traffic is being monitored, it is logical to assume that
eight zeros will transmit within a reasonable time period. However, if a pattern
is transmitted, refer to section 2-43 to ensure that the particular pattern being
received allows eight consecutive zeros. Monitor the green Pattern LEDs to
determine if a pattern is being recognized by the test set.
Signaling Type Selected
Robbed Bit
Robbed Bit
Robbed Bit
CCIS or E-Bit
CCIS
E-Bit
Not Applicable
Overview
2
Indicators
Signaling Bits
A, B
A, B, C, D
A, B
A, B
A, B
A, B, C, D
None
2-23
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