How can I couple these three devices so that no interfering external radio comes in? And are there really 16 channels? I can only select up to 8 channels at a time. Thanks for the help!
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.