Test Loop Access; Gnlb Loopback Test Procedures - ADC HiGain HLU-200 List 2D User Manual

GNLB Loopback Test Procedures

T L A
EST OOP CCESS
The HLU-200, List 2D supports the same Test Loop function that most other Litespan channel units support. The
block diagram of this function is shown in
from the outside cable pairs pass through a set of relay contacts before they are connected to the HLU-200. This
allows each of the two incoming loops to be disconnected from the HLU-200 whenever these relays are energized
by Litecraft or TL1 commands. The energized relays then route the outside cable pairs over the Narrow Band Test
Loops 1 and 2 bus to the MTAU unit which can then perform standard cable pair tests on each of the two loops.
The Litecraft/TL1 commands that initiate this test access are listed in
To access the test loop commands:
1 Highlight either the HTU-R or the CBA boxes in the Channel Bank screen of
Figure 9 on page
2 Select either Maintenance | MTAU | Connect to MTAU to connect the HDSL pairs to the MTAU or
Maintenance | MTAU | Disconnect from MTAU to reconnect the HDSL pairs to the AHDSL unit.
Use this test loop command with caution since it opens the HDSL pairs and forces the circuit
completely out of service. Also, to avoid undue stress on the relay contacts, and unwanted
voltage on the cable pairs whose slow decay may cause misleading test measurements, remove
the HDSL voltage from the two loops prior to initiating the test loop command. This is done by
issuing the ED HDSL LP SINK command listed in
voltage after the tests are finished and the Test Off command has been sent, issue the ED HDSL
LP SOURCE command listed in
pairs.
Version 2.0 of Litecraft only supports the CONN to MTAU command. The DISC command is not
available. Therefore the CONN command should never be issued. If the CONN command is
inadvertently issued, the HLU-200 List 2D must be unplugged from its slot, reseated and
reinstalled to reconnect HDSL pairs and restore the HLU to its normal operating state.
GNLB L
OOPBACK
Testing allows verification of the integrity of the HDSL channels at every module location as well as the DS-1
channels to the customer and the remote/local T1 interface. If trouble is encountered on the HLU-200 List 2D
Litespan 2000 Interface, verify that the HLU-200 List 2D is making a positive connection to the CBA backplane.
To perform the GNLB loopback test procedure:
1 Have the CO tester send the HRU (3 in 7) in-band loop-up code for five seconds. Observe that an HRU
"NREM" loopback is in effect (see
loopback state is indicated by the GREEN LOOP LED on the front panel and is also displayed in the Span
Status screen.
2 Have the CO tester transmit a T1 test signal into the HLU-200 and verify that the returned (looped) signal is
error free.
3 If the above test fails, have the CO tester transmit the (3 in 5) in-band loop-down code.
30
Figure 3 on page
15.
Table 5 on page
T
EST
Figure 24 on page 27
February 10, 1999
6. Each of the two HDSL loops (Loop 1 and Loop 2)
Table 4 on page 10
Table 5 on page 11. To restore the HDSL
11. This restores the HDSL voltage to the cable
P
ROCEDURES
for non-doubler loopback configurations). The
150-200-124-02, Issue 2
below.
HLU-200 List 2D