ADTRAN 4200659L1 - Manual (Page 127)

Chapter 6. Diagnostics
61200659L1-1 MX2800 STS-1 User Manual 6-5
CSU Loopback
A CSU L OOPBACK enables the MX2800 STS-1 to generate a CSU
loop-up pattern (001001…) towards the T1 CSU attached to the
selected T1 line for six seconds. After six seconds have elapsed, the
pattern will cease and incoming network traffic will be passed
through to the CSU device. If the CSU device responded to the
CSU loop-up pattern, it will return all data back towards the
network. A loop-down pattern (0000100001….) will be generated
towards the CSU for six seconds when
D ATA M ODE is selected.
CSU Loopback w/BERT
A CSU L OOPBACK W /BERT enables the MX2800 STS-1 to test the
local T1 loop to the CSU using the standard QRSS pseudo-random
bit sequence. When
CSU L OOPBACK W /BERT is selected, the
MX2800 STS-1 will initiate a CSU loopback towards the CSU
attached to the selected T1 line similar to the
CSU L OOPBACK test
above. Six seconds after starting the CSU loop-up pattern, the
MX2800 STS-1 will cease sending the CSU loop-up pattern and
begin sending an unframed 511 pattern towards the CSU. If the
CSU device responded to the CSU loop-up pattern, the
MX2800 STS-1 will check the incoming pattern for errors.
Additional menu items will appear to show the state of pattern
synchronization, error count, and a clear error count option (see
Figure 6-7 on page 6-6). Selecting
D ATA M ODE will cease the
transmission of the QRSS pattern and start transmission of a loop-
down pattern as previously described.
When in CSU L OOPBACK , only the D ATA M ODE for the T1 under test
may be selected. Selecting any other option will result in an error
message being displayed.