Unlike citizens-band radios (CBs) that require mobile users to be close to each other, a car phone works by cellular radio. It is a phone that keeps its connection while the user is mobile by continuously checking its immediate neighborhood for repeater stations and rapidly switching to a new station when out of range of the last one. The switching takes place so rapidly (0.3 seconds) that human conversations are not interrupted.
In February 1991 the U.S. Federal Communications Commission (FCC) approved 3 experimental pocket phone systems in Atlanta, Boston, and Long Island by 3 different U.S. cable companies. These phones fit in a shirt pocket and do not require any other equipment; low-power radio towers throughout each city pick up their weak broadcasts and computers route the traffic to the appropriate person. These phones can be used anywhere in the city. In September 1991 the British-based satellite consortium Inmarsat announced plans to launch 30 to 40 satellites to do the same for pocket phones, but worldwide. And Motorola is petitioning the FCC to approve its Iridium Project: a plan to launch dozens of low-power microsatellites that would do the same for portable computers--again worldwide.
There are now almost 7 million cellular phone users in the U.S., and the number of cellular phones is doubling every year .