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Knowledge document #183

Configuring a combined telephone/fax machine in the FRITZ!Box

You can connect a combined telephone/fax machine to an analog extension or the "FON S0" socket on the FRITZ!Box and use it to send faxes and make telephone calls.

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

1 Configuring a combined telephone/fax machine

Configure the combined telephone/fax machine as a fax machine in the FRITZ!Box:

  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 socket the fax machine is connected to when configuring it, another telephony device was already configured for that socket. Delete that device.
  6. If the fax machine is connected to the "FON S0" socket on the FRITZ!Box, during setup you will be shown which telephone numbers to assign to the fax machine. If the fax machine is connected via an ISDN telephone system, you must assign the telephone numbers to the port on the ISDN telephone system that the fax machine is connected to.

2 Disabling fax transmission with T.38

  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. Click "Changing the Settings" in the "Telephony connection" section to display all of the settings.
  5. Disable the option "Fax transmission using T.38".

    Note:The T.38 standard (Fax over IP) allows reliable fax transmission over the internet. However, when T.38 is enabled, you cannot use the combination device to conduct calls over the internet. When faxing over the internet without T.38, faxes may not be transmitted properly.

  6. Click "Apply" to save the settings.
    • Test whether you can send faxes.
  8. If you cannot send faxes, enable the option "Fax transmission using T.38". If you are then able to send faxes, either leave T.38 enabled and only use the combination device for faxing, or disable T.38 and only use the combination device for conducting calls.
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