Monitoring and Testing
4-113163-A2-GB20-10 March 1999

Sending a V.54/ANSI FT1

Activation/Deactivation

"Procedure
To send a V.54 or ANSI FT1 Activation or
Deactivation loopback sequence to the far-end DSU/CSU:
1. From the top-level menu screen, select Test.
2. From the Test screen, select Rlpbk.
F1
Test:
Rlpbk Lpbk Ptrns
F2 F3
3. From the Rem Loopback screen, press the
function key that corresponds to the specific
loopback test you want to perform. Use the scroll
keys, if necessary.
F1
Rem Loopback:
LLBUPLLBDN 54UP
F2 F3
The 54UP, 54DN, FT1UP, and FT1DN commands
send the requested sequence out the network
interface on the DS0 channels allocated to Port 1.
The sequence is sent to the far-end DSU/CSU.
During this time, Sending appears on Line 2 of
the LCD, followed by Command Complete when
the sequence is complete.
During the Sending message, you can press the
and keys without affecting transmission
of the loopback sequence.
Local Loopback Tests
The Local Loopback tests enable you to conduct circuit
testing and fault isolation for the digital line. The
supported local loopback tests are:
•Line Loopback (LLB)
•Payload Loopback (PLB)
•Repeater Loopback (RLB)
•Data Channel Loopback (DCLB)
•Data Terminal Loopback (DTLB)
The Line Loopback command can be activated and
deactivated in response to commands received over the
network interface. The Network Interface configuration
option NET LLB controls whether the DSU/CSU
responds to the commands transmitted on the network
interface to initiate LLBs (see Appendix C, Configuration
Options).
The data port configuration option NET DCLB
controls whether the DSU/CSU responds to inband V.54
commands to initiate DCLB for that port (see
Appendix C, Configuration Options).
Local loopback tests can be aborted (Abort Command)
at any time.
No more than two local loopbacks can be active at any
one time. An additional restriction prohibits certain
loopbacks from running at the same time. Valid loopback
combinations listed in Table 4-5 are identified by YES.
Table 4-5
Valid Loopback Combinations
LLB PLB RLB DCLB DTLB
LLB N/A NO YES NO YES
PLB NO N/A NO NO YES
RLB YES NO N/A NO YES
DCLB NO NO NO NO NO
DTLB YES YES YES NO NO