150-388-151-01, Revision 01
Troubleshooting
HLU-388 List 5A
September 15, 1999
45
L
OOPBACK
O
PERATION
HiGain has a family of loopback options for analyzing circuit functionality. The loopback signal is transmitted
and returned to the sending device for comparison. This allows you to verify the integrity of the HDSL channels
to the HLU, the HLU DSX-1 interface and the DS1 channels to the customer. Loopback options include:
•
Generic Loopback (GNLB) options, including the SmartJack (SMJK) option (
)
•
Special Loopback (SPLB) options, including
“Special Loopback Commands” on page 47
and the following
tables:
–
Addressable Repeater Loopback commands: A1LB, A2LB, A5LB (
)
–
Addressable Repeater Loopback commands: A3LB, A4LB (
)
Loopback commands can be initiated by:
•
selecting the loopback type using the MODE and SEL buttons on the HLU (or the Manual Loopback button
on the HRU)
•
selecting the loopback type from the Maintenance Terminal Main Menu when connected to the craft port of
the HLU or HRU
•
entering the loopback code into the test equipment connected to the HLU or HRU
Generic Loopback Commands
The HiGain Generic Loopback (GNLB) commands allow you to use inband codes to loop up either NLOC
(4-in-7) or NREM (3-in-7) towards the network. In addition, these inband codes loop up CREM (6-in-7) or CLOC
(5-in-7) towards the customer. Either loopup condition can be terminated (looped down) with the 3-in-5 SMJK
loopdown code. All inband codes must be present for 5 seconds before the HiGain system responds. HiGain also
supports NDUn doubler loopbacks to the network and CDUn doubler loopbacks towards the customer.
summarizes the available loopbacks in the system, and
summarizes the HiGain
generic loopback commands. See
“GNLB Test Procedures” on page 49
for the test procedures that apply when
using the GNLB mode.
Figure 27.
Loopback Summary
Network
Customer
Premises
Activate loopback using
one of the following:
• MODE/SEL buttons
• Maintenance Terminal
• Test Set
Activate loopback using
one of the following:
• Loopback button
• Maintenance Terminal
• Test Set
HLU
HDU
HDU
HRU
NLOC
NDU1
NDU2
NREM
SMJK
TLOS
CREM
CDU1
CDU2
CLOC