and
third generation
The difference between telephones is that:
Satellite phones rely on global satellites.
Communication system
To do the data
trait
Image transmission, seamless network.
3G mobile phones rely on
ground
base station
It was transmitted by Jingxing.
The principle of early telephone is that sound is a compound vibration in the air, which can be transmitted to.
solid
Go, pass
electric pulse
Transfer on conductive metal. Bell applied for the telephone patent in March 1876.