FRITZ!Box 7340 Service - Knowledge Base

FRITZ!Box 7340 Service

Cannot send or receive faxes with external fax machine

You cannot send or receive faxes (over the Internet and/or landline) with a fax machine connected to the FRITZ!Box, although you can conduct incoming and outgoing telephone calls. 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 Installing the latest FRITZ!OS for the FRITZ!Box

2 Enabling fax transmission with T.38

If you would like to use an Internet telephone number for faxing, then you must enable T.38 (fax over IP) for fax transmission in the FRITZ!Box. With T.38, a special network protocol is used for fax transmission instead of fax tones. As a result, transmission is significantly less susceptible to interference:

  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 option "Fax transmission using T.38" in the "Voice Packets" section.
  5. Click "Apply" to save your settings.

3 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. Click on the "Telephony" tab.
  4. Check whether one of the following error messages is displayed in the event log after faxing fails, and note the corresponding information:
    • "Unsupported Media Type (415)"
      • Your Internet telephony provider does not support a requested codec or does not allow fax transmission as a rule.
    • "Not Acceptable Here (488)" or "Gewünschter Rufaufbau wird nicht unterstützt (606)"
      • Your Internet telephony provider does not support the T.38 standard. Without T.38 (Fax over IP), fax transmission over the Internet is not reliable.
        • Disable T.38 in the FRITZ!Box user interface. You may be able to send and receive faxes without using T.38.

          Note:If you cannot send and receive faxes without using T.38, then you can use an Internet number of an Internet telephony provider that does support T.38 for faxing. 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.

4 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 recognizes whether an incoming call is a voice call or a fax call and automatically forwards faxes to a fax machine configured in the FRITZ!Box:

Important:A different device, for example a telephone or answering machine, must accept the call first in order for the fax switch to recognize faxes and forward them. 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, then you did not configure your landline yet:
  5. Click "Apply" to save your settings.

5 Reconfiguring the fax machine

  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.

    Important:If you cannot select the extension the fax machine is connected to when configuring it, then a different telephony device has already been configured for this extension. You must delete this device first.

6 Testing fax transmission to various remote fax machines

  • 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.

7 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.

8 Enabling the error correction mode (ECM) for testing purposes

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.

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

9 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:
    • If "T.38" is displayed:
      • The standard T.38 was used for this fax transmission.
    • If "T.38" is not displayed:
        The standard T.38 was not used for this fax transmission. Your Internet telephony provider must support the T.38 standard. 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.

10 Fax machine is causing the error

If you are still not able to send or receive a fax using a landline number, 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.