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Functional Description 700-701-100-02
20 August 9, 2002 UTU-701 and ETU-751 List 1
The following applies to LTU and NTU loopbacks:
• No inband loopback codes are recognized or generated.
• A remote HDSL loopback is not available from the local console screen as it causes the HDSL link to go down
and requires user action at the remote unit to disengage the loopback.
Table 12. Loopbacks Selected at Front Panel Pushbuttons and Console Screens
Loopback Description
The two loopbacks that follow can be selected from the LOC and REM front-panel pushbuttons, the console screens, or the
management unit interface.
LOC Pushbutton—Local
HDSL Loopback
This is an analog loopback implemented in both HDSL transceivers, and enables a complete checkout
of the local equipment by looping back data at the furthest point before the transmission media. The
HDSL link goes down as a result of this loopback, and is therefore not selectable from the remote unit
console screens.
REM Pushbutton—Remote
Loopback
Data is transmitted across the HDSL link and looped back at the remote interface ports. The HDSL
link must be up for this loopback to be available. With no HDSL link up, the REM button will not enable
any loopbacks.
The three loopbacks that follow are available exclusively from the console screens or management unit interface.
Local Interface Loopback Data is looped back at the closest point in the local unit toward customer equipment. This loopback
is useful for verification of a proper connection at the local interface between your DTE and the local
HDSL card. The HDSL link is maintained during this loopback.
Local or Interface Loopback
Away from the Local
Equipment
Data is looped back at the local unit or remote unit back toward the remote DTE equipment. This is
equivalent to pressing the REM button on the remote unit’s front panel, and is made available at the
local console screen for ease of installation. The injected test data and loopback verification must still
be performed at the remote unit site. Local equipment outputs an AIS for the duration of this test.
Remote Interface Away
from the Local Equipment
Data is looped back at the remote unit toward the remote DTE equipment. This is available at the local
console screen for the duration of this test. The injected test data and loopback verification must still
be performed at the remote unit site. Local equipment outputs an AIS for the duration of this test.