Motorola 68230 - Vanguard 300 DSU/CSU Operator's Manual page 71

DSU Troubleshooting
Introduction
Use the following information to help troubleshoot potential installation
problems.
Potential Installation Problems
Installation problems may include the following:
Improper telephone company interface connection
Incorrect DSU port Clock Source option
No signal from telephone company interface
CTP-Derived Information
The following information may be derived from the CTP.
Function
Node Statistics
Port Statistics
Monitor
DSU Internal Loopback
used to...
verify that the software is a version that contains
the DSU option modifications.
show if the software recognizes the DSU.
verify that data is sent without error; error counts
may denote an error in clocking mode
configuration.
show if the software recognizes the DSU.
determine, via input/output signals, if the DSU
option is in a loopback mode requested by the
remote end (which would result in an inability to
send data); continuous bipolar violations indicate
the remote system is out of service.
indicate a failure of this loopback mode, meaning
a connection has not been made.