Mercedes-Benz M-Class 2008 Owners Manual - Manual (Page 309)

308
Controls in detail
Useful features
Infrared reflecting windshield*
1 Infrared transparent areas
Infrared reflecting glass reduces the
amount of radiated heat entering the vehi-
cle interior through the windows.
The infrared reflecting glass also prevents
the transmission of signals through the
glass by in-vehicle electronic devices, e.g.
electronic toll collection devices.
To allow the use of these devices in the
vehicle, three infrared transparent
areas
1 are placed in the windshield.