^{In the days before cell phones, people who needed mobile-communication ability installed radio telephones in their cars. In the radio-telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower.}

^{This central antenna meant that the phone in your car needed a very powerful transmitter; one big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use them as there just were just not enough channels to go around. (Remember the ol' *party line*?)}

^{The genius of the cell system is the division of a city into small cells (ergo the name - cell phone) that allows extensive frequency re-use across an area so that millions of people can use cell phones at the same time.}

^{In the atypical analog cell phone system of the USA, the cell phone carrier receives about 800 frequencies to use across a city. The carrier chops up the city into cells. Each cell is typically sized at about 10 square miles (26 square kilometers).}

^{A single cell in an analog system uses one-seventh of the available duplex voice channels. That is, each cell (of the seven on a hexagonal grid) is using one-seventh of the available channels so it has a unique set of frequencies and there are no collisions: In other words, in any cell, many people can all be talking on their cell phone at the same time.}

^{With digital transmission methods, the number of available channels increases. Some digital systems can carry three times as many calls as an analog system can.}

^{If you take a cell phone apart, there isn't much there...you find that it contains just a few individual parts: A circuit board (which contains the "brains" of the phone) An antenna A liquid crystal display or more commonly called a (LCD) A keyboard A microphone A speaker and A battery.}

^{The GSM standard for digital cell phones was established in Europe in the mid-1980's; long before digital cell phones became common place in America. Cell phones are more popular in Europe than they in the United States with more than 60 percent of Europeans owning a cell phone; compared to about 40 percent of Americans owning a cell phone.}

^{About 32% of American teenagers (more girls than boys) own a cell phone now and it is also possible to locate a person using a cellular phone down to a range of a few meters anywhere in the world.}

^{There are dozens of reason cell phones are so popular; some of them are the obvious.}

^{1-Handy in an Emergency}

^{2-Your child can always phone home}

^{3-Handy to phone when away from home as pay phone booths}

^{barely exist anymore.}

^{4-Some of them are untraceable such as the Tracfone tm}

^{5-To quickly report a crime in progress}

^{6-To call for help if you are being threatened, like someone}

^{is trying to get into your car}

^{brought to you by:}

^{http://www.unlisted-etcetera.com}