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Knowledge document #3696
FRITZ!DECT 440
This support document is available for the following products:

The display of the FRITZ!DECT smart switch is frozen

The display of the FRITZ!DECT smart switch, for example FRITZ!DECT 440, is frozen and shows old values. The smart switch no longer reacts when you push a button and the connection to the FRITZ!Box is interrupted.

1 How the display works

FRITZ!DECT smart switches have energy-saving e-paper displays like the ones used in e-book readers. E-paper displays only require a current flow when changing the display. When the batteries are removed or if they are dead or unsuitable, the last indication remains on the display.

Note:Refer to Wikipedia for more information on how an e-paper display works.

2 Changing batteries

  1. Remove the batteries from the FRITZ!DECT smart switch.
  2. Insert new batteries that are suitable into the FRITZ!DECT smart switch:
    1. Varta Industrial Pro AAA, Varta Longlife Max Power AAA, GP Super Alkaline LR03, or Duracell Industrial AAA are suitable.
    2. Do not use rechargeable batteries. Rechargeable batteries usually have a higher internal resistance and a higher self-discharge rate than disposable batteries and often produce lower voltages. This can affect how the smart switch functions and shorten their service life.
    3. Do not use zinc-carbon batteries. Due to their construction, they are not suitable for use in FRITZ!DECT smart switches.

3 Loading the factory settings

The settings for the smart switch are retained in the FRITZ!Box when the factory settings of the FRITZ!DECT smart switch are loaded:

  1. Push the Menu button for about 2 seconds until the menu is displayed.
  2. In the menu, push the button labeled "Zurücksetzen".

4 Re-registering the FRITZ!DECT smart switch

  1. Register the FRITZ!DECT smart switch with the FRITZ!Box.
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