About Mobile Phones
Cellular, or mobile phones, originally used in cars, airliners, and passenger trains, but increasingly becoming ubiquitous, are basically low-power radio-telephones. Calls go through radio transmitters that are located within small geographical units called cells. Because each cell?s signals are too weak to interfere with those of other cells operating on the same frequencies, more channels can be used than would be possible with high-power radio frequency transmission. Narrow-band frequency modulation (FM) is the most common mode of transmission, and each message is assigned a carrier unique to the cell from which it is transmitted. Since the cellular phone was first tested in 1978, the cellular market in Britain alone had grown at a rapid rate to over 8.5 million users by 1997. In Japan it is as high as one mobile phone per ten people. However, while the number of cellular users has increased, many new subscribers are low users. In the United Kingdom cable operators are gaining some 500,000 extra subscribers per month.
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