Cannot Send or Receive a Fax via Optical Line

The machine conforms to analog line standards, and sending and receiving of faxes via optical line cannot be guaranteed. You may be able to perform operations via optical line, so use the following steps:
Check the Optical Line Provider.
Check with the optical line provider that the following two items are guaranteed:
Call quality equivalent to analog line level
Guaranteed operation of Super G3 (fax communication standard)
Lower the Communication Start Speed and Check the Sending and Receiving Status.
Use the following procedure to lower the communication start speed in phases and check whether you can send and receive faxes:
Cannot Send a Fax
Log in to Remote UI in System Manager Mode [Settings/Registration] [TX Settings] [Fax TX Settings] [Edit] in [TX Start Speed], select the speed [OK]
On the operation panel, select [Menu] in the [Home] screen, and then select [Function Settings] to configure the settings. [TX Start Speed]
Cannot Receive a Fax
Log in to Remote UI in System Manager Mode [Settings/Registration] [RX/Forwarding Settings] [Fax RX Settings] [Edit] in [Basic Settings] in [RX Start Speed], select the speed [OK]
On the operation panel, select [Menu] in the [Home] screen, and then select [Function Settings] to configure the settings. [RX Start Speed]
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