FRITZ!Box 6890 LTE Service - Knowledge Base

FRITZ!Box 6890 LTE Service

Cannot send or receive faxes with external fax machine

Although you configured the fax device according to our guide and can conduct calls over the FRITZ!Box, you cannot send or receive faces. Faxes cannot be transmitted or transmission is aborted. One of the following error messages may be displayed in the event log of the FRITZ!Box:

  • "Not Acceptable Here (488)"
  • "Unsupported Media Type (415)"
  • "Not Acceptable Here (606)"

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface. The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS.

Simply proceed as described below. After each measure, check whether the issue persists.

1 Checking the event log of the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Event Log" in the "System" menu.
  3. Select "Telephony" from the drop-down list.
  4. Check whether one of the following error messages is displayed for a failed fax. If this is the case, note the information that correspond to the message.
  5. If the message "Unsupported Media Type (415) is displayed, then your provider does not support the requested codec or generally does not allow fax transmission.
    • If the message "Not Acceptable Here (488 or 606)" is displayed, then your provider does not support the T.38 standard. Without T.38 (Fax over IP), fax transmission over the Internet is not reliable.

2 Enabling the fax switch (passive)

If you would like to use your analog landline number to receive telephone calls as well as faxes, enable the FRITZ!Box's fax switch. The fax switch automatically forwards faxes to a fax machine configured in the FRITZ!Box:

Important:In order for faxes to be recognized and forwarded, a different device, for example a telephone or answering machine, must accept the call first. The fax switch does not recognize calls that are not accepted.

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click on the "Line Settings" tab.
  4. Enable the passive fax switch. If the option is not available, configure your analog landline number in the FRITZ!Box first. Then you can enable the passive fax switch.
  5. Click "Apply" to save the settings.

3 Reconfiguring the fax machine

Set up the fax machine in the FRITZ!Box, even if it is connected to the FRITZ!Box via an ISDN PBX:

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. If the fax machine is already displayed in the list of telephony devices, click the button (delete) for the fax machine.
  4. Reconfigure the fax machine: Click the "Configure New Device" button and follow the instructions.
  5. If you cannot select the extension the fax device is connected to when configuring it, then another telephony device has already been configured for the extension. You must delete this device first.
  6. If the fax machine is connected to the "FON S0" port on the FRITZ!Box, during the configuration procedure you will be shown which telephone numbers to assign to the fax machine. If the fax machine is connected by means of an ISDN PBX, you must assign the telephone numbers to the extension of the ISDN PBX with the fax machine.

4 Testing different remote sites

  • Test whether you can send a fax to or from different fax machines connected to different telephone lines.
    • If fax transmission only fails with a particular line, then the fax machine at the remote site is either not ready to receive faxes or incorrectly configured.

5 Testing different transmission speeds

Many fax machines allow you to select from various transmission speeds (4800, 7200, 9600, 14400 and 36600 Baud):

  • If your fax machine offers this option, test different transmission speeds one after another. The FRITZ!Box supports fax transmission speeds of up to 14400 Baud.

    Note:You can find information on configuring the transmission speed in its manual, or consult its manufacturer directly.

6 Enabling the error correction mode (ECM)

Using the error correction mode (ECM) with your fax machine can considerably improve the results, as long as the remote machine also supports ECM. However, in some cases the results are worse:

  • Enable the error correction mode (ECM) in your fax machine for testing purposes. Refer to the device's manufacturer for information on how to configure ECM, for example consult the manual.

7 Checking whether T.38 was used for fax transmission

The following steps are only necessary if you would like to use an Internet telephone number to send and/or receive faxes:

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click on the "Voice transmission" tab.
  4. Look for aborted faxes under "Display table on completed telephone calls" and check whether "T.38" is displayed in the "Coding" column for these faxes:
  5. If "T.38" is displayed, then T.38 was used for the fax transmission.
    • If "T.38" is not displayed, then T.38 was not used. Without T.38 (Fax over IP), fax transmission over the Internet is not reliable.

      Note:If your Internet telephony provider does not support T.38, then you can use an Internet number of an Internet telephony provider that does support T.38 to receive faxes. If your FRITZ!Box is connected with a landline (analog or ISDN), you can also use a landline number instead of the Internet number to send faxes.

If you are still not able to send or receive a fax using a landline number, or it is aborted, there are unfortunately no further settings in your FRITZ!Box that influence faxing. In such cases, the problem lies with the fax.

Note:Often, the manufacturer of a fax machine can give you helpful advice on how to ideally configure the fax machine for use with a PBX.