Reason:
The fault may be caused by the following:
The ONU is not registered.
The SS delivers the busy tone signaling.
The data configuration is incorrect.
Soluton:
handle the fault, perform the following operations:
1. Check the data configuration on the SS.
2. Check the data configuration on the ONU and check whether
the configuration is consistent with that on the SS.
3. If the data configuration on both sides is correct, ***yze the
packets through packet capture, which requires the MGCP or
H.248 protocol.

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Helpful.....