FXO Port Voice Quality Issue


When you make call via the FXO port, you would meet the voice quality issue. For instance, voice cut, echo, unclear voice etc. It’s could be setting issue as well as related with the practical line quality.

Try to perform the check list in the following:

Check List:

- Software part

1. Check if you select the right FXO mode as per your country in the General Preference settings.

2. Check if your FXO port volume is proper according to your actual call experience. TxGain means the volume sending out by FXO port, RxGain means the volume receive by FXO port.

3. Try impedance match settings. (* U-Series doesn't support, and please seek help from Yeastar if you are not sure how to configure.)

For FXO gateway:


For S-Series

Refer this guide: FXO Impedance Match Tool Instruction

- Hardware part

* If it is not S-Series, please skip the steps included with EX08 card test.

  1. Connect line with analog phone to test the voice, ensure the line is good.

  2. Swap the FXO port to test.

  3. Swap the IP phone to test.

  4. Swap slot to install the O2 module on the same motherboard/EX08 board to test.

  5. Swap an O2 module, if you have one.

  6. If failure happens on above 5 steps. And if the PBX is installed with the other EX08 board, try to install the O2 module on the other EX08 board to test.


Logging: (If you can’t resolve the issue, please submit the following information to Yeastar support. We would help confirm whether it is hardware issue or not)

  1. The test result of the check list.

  2. The FXO port capture including the issue.

  3. The screentshot of the FXO volume settings.
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