Mobile Phones:
Beginning with 1981 to 1983 in USA were created two cellular system.
In the beginning the use of cell phones were used in vehicles such as taxicab radios, two way radios in police cruisers, and the like. A large community of mobile radio users, known as the mobileers popularized the technology that would eventually give way to the mobile phone. Originally, mobile phones were permanently installed in vehicles, but later versions such as the so-called transportables or "bag phones" were equipped with ciggerette lighter plug so that they could also be carried, and thus could be used as either mobile or as portable phones.
In December 1947 engineers, proposed hexagonal cells for mobile phones. also they proposed that the cell towers be at the corners of the hexagons rather than the centers and have directional antennas that would transmit/receive in 3 directions.
In Europe, radio telephony was first used on the first-class passenger trains between Berlin and Hamburg since 1926. At the same time, radio telephony was introduced on passenger airplanes for air traffic security. Later radio telephony was introduced on a large scale in German tanks during the second world war.