User manual

Diagnostics & Troubleshooting
Testing Low-Speed Interface Operation
7-22 July 2004 Wide Bank 28 DS3 - Release 2.4
DS1 NIU Loopback
The Wide Bank provides NIU loopback capability toward the DS3 network. To test its
functionality, use a test set on the DS3 interface to inject NIU loop codes toward the low-speed
interfaces.
NOTE: This test can also be performed with two Wide Banks as shown on the next
page.
Figure 7-12 Low-Speed NIU Loopback
1. Enable loop code detection.
(A:Active)> ds1 1 loopdetect on
2. Use test set on DS3 side to inject an NIU Loop Up code to low-speed circuit #1.
(Loop Up code is 11000).
3. Inject a test pattern of your choice (QRSS, PRBS, and so on).
4. Verify that the loop experiences no bit errors.
5. Verify that the test set connected to the low-speed circuit #1 is receiving AIS.
6. Inject an NIU Loop Down code toward the low-speed circuit #1 from the test set (Loop
Down code is 11100).
7. Verify that low-speed circuit #1 returns to normal operation.
8. Disable loop code detection.
(A:Active)> ds1 1 loopdetect off
9. Repeat steps 1 to 8 for the remaining low-speed circuit interfaces.
Send AIS
Relays
Trans-
ceiver
Selector
M13
Framer
Trans-
ceiver
Relays
LS Card HS Card
Toward DS1/E1
DS1/E1 DS3
Loopback
Toward DS3
NIU Loop-Up
From Test Set
NIU Loop Detect
Must be Enabled