FRITZ!Box 7583 Service - Knowledge Base

FRITZ!Box 7583 Service

Cannot send or receive faxes with an external fax machine

Although the fax machine was configured according to our guide and you can conduct calls over the FRITZ!Box, you are either sometimes or never able to send or receive faxes. 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)"

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

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

1 Installing the latest FRITZ!OS for the FRITZ!Box

2 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, your provider does not support the requested codec or does not allow fax transmission.
    • If the message "Not Acceptable Here (488 or 606)" is displayed, your provider does not support the T.38 standard. Without T.38 (Fax over IP), fax transmission over the internet is not reliable.

      Note:In this case, you can either use a telephone number from a provider that supports T.38 or disable T.38 again for fax reception. T.38 may not be necessary for fax transmission.

3 Setting your fax machine to tone dialing

  1. Set your device to "tone dialing" (DTMF) and not "pulse dialing". If tone dialing is selected, you hear a tone when you press a number key; with pulse dialing, you hear clicking sounds. Refer to the device's manufacturer for information on how to set it up, for example consult the manual.

4 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 (Delete) button 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 port the fax machine is connected to when configuring it, another telephony device has already been configured for the port. Delete that device first.
  6. If the fax machine is connected to the "FON S0" port on the FRITZ!Box, during configuration you will be shown which telephone numbers to assign to the fax machine. If the fax machine is connected via an ISDN PBX, you must assign the telephone numbers to the port on the ISDN PBX that the fax machine is connected to.

5 Testing different remote sites

  1. Test fax transmission from or to different fax machines on different telephone lines.
  2. If fax transmission only fails with a particular remote site, then the fax machine at the remote site is either not ready to receive faxes or incorrectly configured.

6 Testing different transmission speeds

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

  1. If possible with your fax machine, test the different transmission speeds one after the other. The FRITZ!Box supports 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.

7 Enabling the error correction mode (ECM)

Using the error correction mode (ECM) on your fax machine can significantly improve the faxing results, as long as the remote machine also supports ECM. In some cases, however, the results may be worse:

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

8 Checking whether T.38 was used for fax transmission

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Numbers" in the "Telephony" menu.
  3. Click on the "Voice transmission" tab. If the tab is not displayed, enable the Advanced View.
  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, you can use an internet telephone number of an internet telephony provider that supports T.38 for faxing.