Maintenance
4-113160-A2-GB21-50 January 1997
Troubleshooting

The DSU/CSU is designed to provide you with

trouble-free service. However, Table 4-6 gives you some

direction if a problem occurs.

For problems other than those listed in the table, please

contact your service representative.

Table 4-6

(1 of 2)

Troubleshooting

Symptom Possible Cause Solutions

No power 1. The power module is not securely attached.
2. The wall receptacle has no power.
1. Check the power module attachment.
2. Check the wall receptacle power by plugging
in some equipment that is known to be
working.
Power-Up
Self-Test fails The DSU/CSU has detected an internal hardware
failure. Contact your service representative.
Message LOS at
NET appears 1. Network cable problem.
2. No signal is being transmitted at the far-end.
3. Facility problem.
1. Check that the network cable is securely
attached at both ends.
2. Check the far-end status.
3. Contact your facility provider.
Message LOS at
DTE appears 1. DTE Drop/Insert (DSX-1) cable problem.
2. No signal being transmitted from the DTE.
1. Check that the DTE Drop/Insert (DSX-1) cable
is securely attached at both ends.
2. Check the DTE status.
Message OOF at
Net appears 1. Incompatible framing format between the
network and the DSU/CSU.
2. Network cabling problem.
3. Facility problem.
1. Check that the framing format for the network
interface is correct.
2. Check that the network cable is securely
attached at both ends.
3. Contact your facility provider.
Message OOF at
DTE appears 1. Incompatible framing format between the
Drop/Insert port on the customer premises
equipment and the DSU/CSU.
2. DTE Drop/Insert (DSX-1) cabling problem.
1. Check that the framing format for the DTE
Drop/Insert (DSX-1) interface is correct.
2. Check that the DTE Drop/Insert (DSX-1) cable
is securely attached at both ends.
Message
Yellow at Net
appears
1. Network cable problem.
2. Far-end device has lost framing sync on the
line.
3. Facility problem.
1. Check that your network cable is securely
attached at both ends.
2. Check the status of the far-end device.
3. Contact your facility provider.
Message
Yellow at DTE
appears
DTE has detected an LOS or LOF condition. 1. Check the status of the DTE.
2. Check that the DTE Drop/Insert (DSX-1) cable
is securely attached at both ends.
Message
AIS at Net
appears
1. Upstream device is transmitting an AIS.
2. The network is transmitting an AIS.
1. Check the status of the upstream device(s).
2. Contact your facility provider.