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LTPH-UM-1031-03, Issue 3 Testing
H4TU-C-319 List 1 September 12, 2003 51
GNLB Test Procedures
Figure 29 on page 50 is a graphical representation of the various loopback configurations with the associated
GNLB commands shown. Refer to Table 16 for a description of these commands.
Table 16. Summary of HDSL4 Loopback and Activation Codes
Method of Activation
Loopback Code Description Test Set Craft Port MODE/SEL
NLOC 1111000
4-in-7
DSX-1 signal is looped back to the network at
the H4TU-C.
X X X
NREM 1110000
3-in-7
DSX-1 signal is looped back to the network at
the H4TU-R.
X X X
NDU1 110000
2-in-6
Signal is looped back to the network at H4D1.
X X X
CDU1 111100
4-in-6
DS1 signal from customer is looped back to the
customer at H4D1.
X X X
NDU2 111000
3-in-6
Signal is looped back to the network at H4D2.
X X X
CDU2 111110
5-in-6
DS1 signal from customer is looped back tot he
customer at H4D2.
X X X
D1LB Dual loopback at H4D1. X
D2LB Dual loopback at H4D2. X
CLOC 1111100
5-in-7
DS1 signal from the customer is looped back to
the customer at the H4TU-R.
X X X
CREM 1111110
6-in-7
DS1 signal from the customer is looped back to
the customer at the H4TU-C.
X X X
COLB Dual loopback at the H4TU-C. DSX-1 signal is
looped back to the network at the H4TU-C and
DS1 signal from the customer is looped back to
the customer at the H4TU-C.
X
RULB Dual loopback at the H4TU-R. DSX-1 signal is
looped back to the network at the H4TU-R and
DS1 signal from the customer is looped back to
the customer at the H4TU-R.
X
SMJK LpUp
(PL)
11000
2-in-5
SmartJack Loopup or NID payload (PL) code.
Invokes H4TU-R loopback towards network.
X
SMJK LpUp
(ESF-DL)
1111-1111-
0100-1000
SmartJack Loopup or NID (ESF-DL) code.
Invokes H4TU-R loopback towards network.
X
SMJK LpDn
(PL)
11100
3-in-5
SmartJack Loopdown or NID payload (PL) code.
Removes SMJK, NLOC, NREM, CLOC, and
CREM.
X
SMJK LpDn
(ESF-DL)
1111-1111-
0010-0100
SmartJack Loopdown or NID (ESF-DL) code.
Removes SMJK, NLOC, NREM, CLOC, and
CREM.
X