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150-388-125-01, Revision 01
Loopback Operation
HLU-388 List 2E
September 15, 1998
39
L
OOPBACK
T
EST
P
ROCEDURES
The following sections provide step-by-step test procedures for the HLU-388 as a function of the loopback option
selected. These procedures allow verification of the integrity of the HDSL channels at every module location as
well as the DS1 channels to the customer and the local DSX-1 interface.
If trouble is encountered on the HLU-388 DSX-1 interface, verify that the HLU is making a positive connection
with its mounting assembly (shelf) connector. Also, verify that the HLU internal equalizer is set to the correct
distance range per
. All equalizers should be set to the distance from the DSX-1 to the shelf.
The transmit and receive T1 DSX-1 ports have splitting access jacks and miniature, 210-series, bridging jacks as
shown in
. Connecting one cable between the two bridging jacks and another between the two
SPAN jacks splits the XMT and RCV and creates metallic loopbacks towards both the DSX-1 and the HLU-388.
If separate plugs are inserted into both SPAN jacks with the other end disconnected, the BRG jacks can be used
to send and receive test patterns towards the DSX-1.
L
OOPBACK
O
PERATION
W
ITHOUT
D
OUBLERS
The complete family of loopbacks that a HiGain system without doublers can execute is shown in
. The
loopbacks can be initiated from the HLU RS-232 Craft port, the HLU front-panel MODE and SEL buttons, or
from a family of Special Loopback (SPLP) in-band loopback commands.
Figure 21.
HLU-388 Non-Doubler Loopback Configurations
CI/DS1
DSX-1
* The Smart-Jack loopback is a metallic loopback in the HRU Lists 6 and 7. It is a logic loopback
in HRU Lists 1 through 5.
** Set the SAIS option to ENA to send the AIS pattern to the CI during Smart-Jack Loopback.
Loopbacks
toward
customer
AIS
HDSL
AIS
HRU
CLOC
HDSL
5 in 7
6 in 7
HRU
HLU
CREM
HLU
Loopbacks
toward
network
HDSL
HLU
NLOC
AIS
AIS
AIS**
AIS
HRU
TLOS
SMJK*
NREM
HRU
HRU
HDSL
HDSL
HDSL
HLU
HLU
2 in 5
3 in 7
LOGIC
4 in 7
HRU
HLU