How does Themo Control's offline mode work?

Themo Portal may sometimes show that a device is offline. 

However, offline mode does not mean that the device has stopped working. When the internet connection is lost, Themo switches to offline mode and starts monitoring the temperature set in Themo Portal. This ensures that the temperature is maintained in the floors and energy is saved even during possible temporary connection interruptions. When the network connection is restored, the device continues to follow the heating program.

The device also needs a continuous power supply in offline mode.