Volkswagen Eos Owner's Manual page 115

Windshield made of heat-insulating glass
Fig. 86 Heat-reflective windshield with communications window (blue shaded area).
Please first read and note the introductory information and heed the WARNINGS
Windshields made of insulating glass have a transparent metallic infrared-reflecting coating. There is
an uncoated area (communications window) just above the inside rearview mirror ⇒
f ig. 86. This
serves as a communications window for transmitting signals to and from electronic components and
accessories.
The uncoated area must not be blocked on the inside or outside or covered with stickers because this
can cause the electronic components to malfunction.