ADTRAN 1200063L1, Manual

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Chapter 3. Operation
3-4 DSU III TDM User Manual 61200063L1-20
No wink from CO Switched 56 provider has encountered a service
problem (4-wire Switched 56).
Not Installed No dial backup option is installed in the DSU III
TDM.
OOS/OOF From
Net Out-of-service signal or out-of -frame condition
exists. The call cannot be completed because either
the called terminal or the called terminal's access
line is out-of-service or is faulty (2-wire and 4-wire
Switched 56).
Open Loop The physical connection to the backup line has been
broken (2-wire and 4-wire Switched 56).
DBU Line in RDL Remote end has initiated a test.
Test From Telco
The network provider has activated the CSU
Loopback (2-wire and 4-wire Switched 56).
DBU Test Pattern The DSU III TDM is currently performing a test with
a pattern.
Waiting for Call The answering DSU III TDM is waiting on a call
from the remote end.