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DSU Operations
5-213610-A2-GB41-60 March 1999
Selecting Aggr (Aggregate) loops back the
user-transmitted data and the secondary channel transport
data (if nondisruptive diagnostics are in effect). This
disrupts secondary channel transport communications.
Selecting Prt1 (Port 1) causes the loopback to occur at a
point where the secondary channel transport has already
been extracted from the user-transmitted data, so only the
user-transmitted data is looped back. Secondary channel
communications are preserved.
To access Digital Loopback from the top-level menu,
make the following selections:
• Local (F1), Remot (F2) and Address
• Test
• DSU or DBM (select active core)
• Lpbk
• DL
• Port Select (when not operating in single-port
mode)
NOTE
When the local DSU initiates
Digital Loopback to a remote
DSU (via Remote mode), the
remote DSU is placed in Test
mode. The local DSU is not in
Test mode, and another test,
such as BERT, can be initiated at
the local DSU.
For TDM or MCMP mode, the following additional
menu appears:
F1
Port Number:
Prt1 Prt2 Prt3
F2
F3
Prt5 Prt6 AggrPrt4
In Bridge mode, you are not asked to select a port; you
are placed in the same loopback configuration as Basic
mode. For MCMP mode, Digital Loopback using the
Aggr selection is not a valid command.
Results
The TXD, RXD, and RTS LED indicators show the
states of the leads at the DTE interface.
F1
DSU Digital Lpbk:
Command Complete
F2
F3