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Knowledge document #65

Cannot register a cordless telephone

Registration of a cordless telephone fails. The following messages are displayed:

  • In the FRITZ!Box user interface: "Registration with the DECT base station failed. The reason for the error is displayed on the cordless (DECT) telephone"
  • On the telephone's display: Registration at Base 1, 2, 3 or 4 failed" or "Search for base"

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

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

1 Maximum number has been reached

You can register up to six cordless telephones, DECT headsets, or DECT door intercom systems with the FRITZ!Box. If six telephones or four telephones, a headset, and one door intercom system have already been registered, you cannot register any more telephones.

Note:You can delete telephones that you are no longer using under "Telephony > Telephony Devices" in the FRITZ!Box user interface.

2 Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Restart" tab.
  4. Click the "Restart" button.

3 Unlocking the buttons

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Buttons and LEDs" in the "System" menu.
  3. Click on the "Keylock" tab.
  4. Disable the "Buttons locked" checkbox.
  5. Click "Apply" to save the settings.

4 Checking whether the telephone supports DECT-GAP

The telephone must support the DECT-GAP profile. DECT-GAP is a common standard for cordless telephones and wireless data transmission that is supported by all FRITZ!Fon models, for example:

  1. Check the telephone's manual or ask the manufacturer whether the telephone supports the DECT-GAP profile. If it does not support DECT-GAP, we do not guarantee that it will function with the FRITZ!Box.

5 Disabling "DECT Eco"

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "DECT" in the "Telephony" menu.
  3. Disable the option "DECT Eco" in the section "Radio Field Strength".
  4. Click "Apply" to save the settings.

Do not re-enable the "DECT Eco" option until you have successfully registered the telephone with the FRITZ!Box.

6 Setting a PIN

You may be using an incorrect PIN to register the telephone with the FRITZ!Box. Therefore, set a new PIN for the FRITZ!Box's base station:

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "DECT" in the "Telephony" menu.
  3. Enter a four-digit PIN in the section "Registration".
  4. Click "Apply" to save the settings.

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

  1. Install the latest FRITZ!OS on the FRITZ!Box.

8 Restoring the telephone to its factory settings

The following steps are only necessary if the problem occurs when using a FRITZ!Fon:

  1. Press the "Menu" key on the telephone.
  2. Scroll to "Settings" and press "OK".
  3. "Reset" > "OK" > "OK"

9 Disabling expanded security functions

The following steps are only necessary if the problem occurs with a cordless telephone from a different manufacturer:

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "DECT" in the "Telephony" menu.
  3. Disable the expanded security functions in the section "Security".
  4. Click "Apply" to save the settings.

10 Resetting FRITZ!Box and using the wizard to register the telephone

Settings in the FRITZ!Box may be preventing the telephone from being registered. Therefore, restore the FRITZ!Box to factory settings and then use the wizard in the FRITZ!Box user interface to register the telephone:

Saving settings of the FRITZ!Box

  1. Save the FRITZ!Box settings.

Saving the FRITZ!Box telephone books

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephone Book" in the "Telephony" menu.
  3. Select a telephone book, click the "Save" button, and save the telephone book as an XML file on your computer.

    Important:If the browser blocks the file download, click "Keep" in Microsoft Edge and Chrome.

  4. Save all of the telephone books stored in the FRITZ!Box, one after the other.

Loading the FRITZ!Box factory settings

  1. Load the FRITZ!Box's factory settings.

Using the FRITZ!Box wizard to register a telephone

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Click the "Configure New Device" button.
  4. Enable the option "Telephone (with or without answering machine)" and click "Next".
  5. Enable the option "Cordless (DECT) telephone" and click "Next".
  6. Start the registration procedure on the telephone, then click "Connect" and follow the instructions.
  7. If you are asked for the PIN of the base station, enter 0000 on your telephone. This is the factory setting of the FRITZ!Box.
  8. If you could successfully register the telephone with the FRITZ!Box, import the telephone books that you saved and reconfigure the FRITZ!Box.

    Important:Do not restore the settings saved in the file "fritzbox[...].export", otherwise the registration of new cordless telephones may fail again.

11 Testing a different telephone

Test whether you can register a different cordless telephone with the FRITZ!Box. Use a telephone that supports the DECT-GAP standard:

  1. Restore the FRITZ!Box settings.
  2. Use the wizard to register the other cordless telephone with the FRITZ!Box.
  3. If you can register the other cordless telephone with the FRITZ!Box, the first telephone is incorrectly configured or defective.
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