[Case Show] Abnormal Ringing and Calls Due to Abnormal Low Voltage and Positive

Fault Description
Ring tones are low for a called party connected to an MA5616. In addition, noises or intermittent voice interruptions occur in calls. A user runs the pots circuit-test command on the service port to perform a circuit line test. Test results show that the low voltage and positive voltage of the power supply for the MA5616 are abnormal.

Possible Cause
- Mains supply voltage is abnormal.
- A voice service board of the MA5616 is faulty.
- A daughter board for the voice service board of the MA5616 is faulty.
- The control board of the MA5616 is faulty.
- The power board of the MA5616 is faulty.
- The subrack backplane of the MA5616 is faulty.

Procedure
1. Test the mains supply voltage. The voltage is normal. Therefore, the fault is not caused by the mains supply.
2. Replace the voice service board, daughter board of the voice service board, control board, power board, and subrack backplane of the MA5616 respectively, and run the pots circuit-test command on the service port to perform a circuit line test. After the subrack backplane is replaced, the test results show that the low voltage and positive voltage of the power supply for the MA5616 are normal. Then the ringing and calls are recovered. The fault is rectified.
 
Suggestion and Summary
Normally, abnormal low voltage and positive voltage of the power supply is caused by a hardware fault. Therefore, when such a fault occurs, replace the hardware to locate the fault.
Abnormal low voltage and positive voltage of the power supply cause abnormal ringing, noises, or intermittent voice interruptions. Abnormal high voltage of the power supply causes no ringing tone or no tone upon off-hook.

Overview of Case Show, click: [Case Show] Interrupted Conversation Because of Improper QoS Configuration of the VoIP Service