[Case Show] Broadcast Is Played After Offhook Because of the Interference on the

Fault Description
A voice user is connected to an ONU in a telecommunications room. The user hears the broadcast after offhook, and the conversation quality is affected.

Cause Analysis
-The ONU is faulty.
-The OLT delivers abnormal information.
-The ONU is interfered.

Procedure
1.Check the data configurations of the ONU and OLT. It is found that the data configurations are correct.
2.Replace the ONU with another ONU of the same type to conduct a test. The user still hears the broadcast, which indicates that the hardware of the ONU is normal.
3.Check the configuration of the softswitch. It is found that the configuration is correct. It is suspected that abnormal data may exist. Capture packets on the OLT and ONU. No abnormal data is found.
4.Remove the voice line from the terminal block, and use a test phone to conduct a test in the telecommunications room. It is found that no broadcast is heard. Connect the loop line to the terminal block, and use the test phone to conduct a test. It is found that the broadcast is heard. Therefore, it can be determined that the loop line is interfered.
5.Check the loop line. It is found that the broadcast tower of a broadcast station is very close to the loop line. The broadcast signals are transmitted to the voice network through the loop line. Reconstruct the loop line. As a result, the fault is rectified.

Suggestion and Conclusion
Electromagnetic devices interfere the communication greatly. Therefore, if noise exists in the conversation, you need to consider whether electromagnetic interference exists on the network.