T1 ESF CSU ACE User Manual Chapter 3. Operation
61204025L1-1B © 2004 ADTRAN, Inc 49
Tests are used to control the activation of loopbacks, the initiation of data test patterns, and self test
execution.
1)LOCAL LOOPBK, Submenu of 4)TEST
Four choices are available for setting the local loopback:
NO LOOPBACK Deactivates the loopback
DTE ON Activates the DTE loopback
LINE ON Activates the line loopback
PAYLOAD ON Activates the payload loopback
Figure 3-20. Local Loopback Test Screen
2)REM LB, Submenu of 4)TEST
Activates the same loopbacks as the LOCAL LOOPBCK but at the far end. This uses either the inband
loop-up code as specified by AT&T 62411 for line loopback (ATT In-Band LLB), or the FDL as
specified in ANSI T1.403 for line loopback codes. An FDL (formerly TABS) maintenance message
corresponding to AT&T TR54016 can be used for payload loopback as well:
NO LOOPBACK Deactivates the loopback
.
AT&T INBAND LLB Activates the line loopback using inband code.
ANSI FDL LLB Initiates the transmission of an FDL line loop-up code toward the far end.
AT&T FDL
PLB Initiates the transmission of the PLB maintenance messages on the FDL.
When a loopback method is selected, the T1 ESF CSU ACE displays LOOPING in the top
right corner of the LCD and the yellow LOOPBACK LED is turned on. When the T1 ESF
CSU ACE determines that the far-end T1 ESF CSU ACE has looped up, the T1 ESF CSU
ACE displays LOOPED. If the T1 ESF CSU ACE does not recognize the remote T1 ESF
CSU ACE looped up after about 10 seconds, the T1 ESF CSU ACE sends the appropriate
loop-down code and displays FAILED, and the LOOPBACK LED is turned off.
Excessive errors on the T1 line can cause this failure. The FDL loopbacks fail if the FDL
is not intact from one end point to the other. FDL loopbacks are valid only in the ESF
framing mode.
