Switching to channels 9-16 is described here: https://www.digitec.ch/de...

Experience shows that there is less "foreign radio" on these channels, our devices have been running on channel 11 for a long time.

These devices use open, licence-free radiotelephony (PMR446). This means that anyone within range on the same channel can listen in and talk. The devices are limited to 8 channels at the time of delivery, as in some countries only these 8 channels may be used. The activation to 16 channels is described in the manual.