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700-701-100-02
Table 11. HDSL Transmission and Application Interface Alarms
Alarm
HDSL Alarms
Margin (MAR)
Errored Seconds (ES)
Loss of Sync Word
(LOSW)
G.703 Alarms
Loss of Signal (LOS)
Loss of Frame Alignment
(LFA)
Receive Alarm Indication
Signal (AIS)
Remote Alarm Indication
Signal (RAI)
Loss of Clock (LOC)
L
OOPBACKS
An HDSL system maintains several diagnostic loopback configurations, both toward and away from the local unit,
which can be used to verify proper transmission of test data through the local unit, the HDSL facility, and the
remote unit.
Figure 8
on
During loopbacks the system generates an Alarm Indication Signal (AIS) past the loopback point toward the far
unit. Loopbacks can be activated from the LOC (local) and REM (remote) front-panel pushbuttons, the console
Test menus, and the management unit interface.
activation methods. Only one loopback option can be enabled at a time. During a loopback, the Loopback LEDs
on the front panel indicate the type of loopback currently present in the system. See
Unit Front Panel LED Indications," on page
The system reverts to normal transmission of payload data after the specified timeout period has elapsed. If a
timeout period is not specified, the loopback must be manually disengaged before normal transmission of data can
resume.
Test loopbacks disrupt normal end-to-end transmission of customer data and are the
equivalent of taking the circuit out of service. The circuit does not revert to normal operation
until loopbacks are disengaged manually or until after the specified loopback timeout period
has expired.
Nx64k
UTU-701 and ETU-751 List 1
Description
HDSL alarms include:
Margin has fallen below threshold set for the HDSL interface.
Errored seconds count has exceeded threshold set for the HDSL interface.
Loss of sync word at the HDSL interface. Remains active during restart, but not a cold start.
G.703 alarms include:
Loss of signal at the G.703 input.
Loss of frame alignment at the G.703 input.
Alarm indication signal (unframed all ones) received at the G.703 input.
Remote alarm indication signal received at the G.703 input (through A-bit).
Applies to loss of external clock when EXT timing is used. The external clock was lost for the
previous second. This alarm is reset when the clock is active again.
page 19
shows all possible loopback paths.
Table 13
6.
LTU Interface
Single-pair
HDSL loop
HDSL
Figure 8. Loopback Operations
August 9, 2002
Table 12
on
page 20
on
page 21
lists loopback equivalents for different
NTU Interface
HDSL
Functional Description
lists available loopbacks.
Table 4, "Line and Desktop
Nx64k
19
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