SMART fortwo coupe Owner's Manual page 209

The maximum transmission output (PEAK) at
the base of the aerial must not exceed the
following values:
Waveband
Tetra
380 - 410 MHz
Mobile communications
generation 2G/3G/4G
The following can be used in the vehicle
without restrictions:
Two-way radios with a maximum trans-
R
mission output of up to 100 mW
Mobile phones (2G/3G/4G)
R
There are no restrictions when positioning
the aerial on the outside of the vehicle for the
following wavebands:
Tetra
R
Mobile communications (2G/3G/4G)
R
Installing two-way radios and mobile phones
Maximum
transmission
output
20 W
6 W
207
Z