Loopback Operation
LTPH-TP-1047-01, Issue 1
28
March 12, 2001
H2TU-R-402 List 5E
Table 11.
Summary of HiGain Loopback Codes and Activation Methods
Method of Activation
Loopback
Code
Description
Test Set
Craft Port
H2TU-C
MODE/SEL
NLOC
1111000
4-in-7
DSX-1 signal is looped back to the network at the H2TU-C.
X
X
X
NREM
1110000
3-in-7
DSX-1 signal is looped back to the network at the H2TU-R.
X
X
X
CLOC
1111100
5-in-7
DS1 signal from the customer is looped back to the
customer at the H2TU-R.
X
X
X
CREM
1111110
6-in-7
DS1 signal from the customer is looped back to the
customer at the H2TU-C.
X
X
X
SMJK LpUp
(PL)
11000
2-in-5
SmartJack Loopup or NID payload (PL) code. Invokes
H2TU-R loopback towards network.
X
SMJK LpUp
(ESF-DL)
1111-1111-
0100-1000
SmartJack Loopup or NID (ESF-DL) code. Invokes
H2TU-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
(a) The RULB dual loopback (same as NREM-CLOC) can be activated by pressing the LBK button on the H2TU-R front panel.
HiGain systems feature the SmartJack (SMJK) option which can emulate a Network Interface
Device (NID) for the purpose of loopback testing of the HiGain circuit. SMJK and NREM
loopbacks perform the same functions, but their initiation differs. SMJK indicates that the
loopback was initiated by the 2-in-5 inband command. NREM, on the other hand, is initiated by
the 3-in-7 inband command, by the H2TU-R front panel LBK button, by a command issued from
the maintenance terminal, or by the H2TU-C front panel MODE and SEL buttons.
Use the inband commands to enable or disable the SMJK loopback options. The HiGain system
setting is normally enabled to recognize all inband SMJK loopback commands.
