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L
OOPBACK
Initiate loopback testing from the maintenance menus. The inband codes shown below can
be sent by a test set.
DSX-1
Network
NLOC
H4TU-C
Downstream
Loopback
Inband Code
NLOC
1111000
NREM
1110000
NDU1
110000
CDU1
111100
NDU2
111000
CDU2
111110
CLOC
1111100
CREM
1111110
SMJK
11000
Loopdown
11100
LED and Status
DSL1
Flashing red once every second Loop 1 of the HDSL4 span connected to H4TU-C is in acquisition.
DSL2
Flashing red once every second Loop 2 of the HDSL4 span connected to H4TU-C is in acquisition.
DSX/DS1
ALM
ESF/SF
Flashing yellow once every second ESF frame formatting and frame error/CRC are present at the H4TU-C.
Flashing green once every second SF frame formatting and frame error are present at the H4TU-C.
B8ZS/AMI
Flashing yellow once every second B8ZS and excess zeros string are present at the H4TU-C.
Flashing green once every second AMI and BPV are present at the H4TU-C.
LBK
Flashing yellow once every second System is ARMed.
T
ESTING
Span 1
CREM
NDU1
H4D1
*
When enabled, TLOS is an automatic loopback
that occurs with an LOS at the remote DS1 input.
Table 1. Loopback Commands
Description
DSX-1 signal is looped back to the network at the H4TU-C.
DSX-1 signal is looped back to the network at the H4TU-R.
Signal is looped back to the network at H4D1.
DS1 signal from customer is looped back to the customer at H4D1.
Signal is looped back to the network at H4D2.
DS1 signal from customer is looped back to the customer at H4D2.
DS1 signal from customer is looped back to the customer at the H4TU-R.
DS1 signal from customer is looped back to the customer at the H4TU-C.
DSX-1 signal is looped back to the network at the H4TU-R SmartJack module.
Deactivates any of the above loopbacks.
Table 2. LED Status and Functions
Function
Solid green Loop 1 of the HDSL4 span connected to H4TU-C has synchronized
without error.
Solid red Loop 1 of the HDSL4 span connected to H4TU-C has detected HBER,
MARG alarm, or any PWRF alarms.
Solid green Loop 2 of the HDSL4 span connected to H4TU-C has synchronized
without error.
Solid red Loop 2 of the HDSL4 span connected to H4TU-C has detected HBER,
MARG alarm, or any PWRF alarms.
Solid green DSX-1 signal at the H4TU-C is error-free.
Solid red LLOS, BPV, frame error, or CRC is detected at H4TU-C. (LED updates
once every second when error occurs.)
OFF DS1 signal is present at both the H4TU-R and H4TU-C.
Solid yellow RLOS is present at the H4TU-R.
Solid red LLOS is present at the H4TU-C.
OFF Unframed DSX-1 is present at the H4TU-C or no DSX-1 is detected at
the H4TU-C.
Solid yellow ESF frame formatting is present at the H4TU-C.
Solid green SF frame formatting is present at the H4TU-C.
OFF No DSX-1 signal is present at the H4TU-C.
Solid yellow B8ZS is provisioned at the H4TU-C.
Solid green AMI is provisioned at the H4TU-C.
OFF H4TU-C is not ARMed or in loopback.
Solid yellow H4TU-C is in either NLOC or CREM (RLB).
Span 2
CDU1
CDU2
NDU2
H4D2
Span 3
NREM
SMJK
CLOC
*
TLOS
DS1
H4TU-R
Upstream
Customer
Premises
H0065-A
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