Cell Phones - Pagers And Cellphone Service

Written by Helen Glenn Court
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As few as seven years ago, cell phones were something of a rarity. I recall my amazement, walking and bicycling across Tokyo and rural Japan in the summer of 1998, for example, that everyone--stress on everyone--seemed to have a cell telephone. In the Washington DC area at the time, by contrast, they were very much the exception. They are now as common as dirt and air everywhere.

We're faced with a bewildering number of options on cell phone providers, manufacturers, models, accessories, plans, rates, deals, and developing technologies. Where do you start? How do cell phones work? Are they a necessity or a luxury? How do know you're getting the best deal?

Cell phones have completely changed the way we communicate forever, but they're based on a simple theory and technology. Alexander Graham Bell invented the telephone in the 1870s. Nikolai Tessla invented the radio in the 1880s. We have both of these men to thank, because cell phone technology is based on the marriage of their inventions.

How Cell Phones Work: Part One

The earliest mobile phones operated from radio antennas. But cities commonly had only one major radio antenna tower with about 25 channels (frequencies), and it took a powerful transmitter to reach that tower. There were decided limitations with this technology.

Cell technology subdivides a city or area into many smaller units--known as a cell--each with its own antenna tower. Think of there being one signal tower for every 10 square miles. Think of radio frequencies being reused. Can you see the number of potential users multiplying almost exponentially? That's what cell technology achieves.

A single cell in an analog system uses one-seventh of the available channels, translating to 56 voice channels. A single cell in a digital system uses one-third of that, translating to 168 voice channels. Cell phones have low-power transmitters that operate on batteries. Base station towers also use very little power because they transmit over the very limited range (those 10 square miles). Can you see all this low use of power equating to low cost? Cell technology is cost effective.

How Cell Phones Work: Part Two

Every cell telephone has a unique identification code--a combination of the electronic serial number of the phone and the mobile telephone number of the user. Each cell phone provider is similarly identified by a system identification code (SID). A control channel is the special frequency on which cell phones and base towers communicate. These ID numbers are programmed into each cell telephone when it is activated by the service provider.

When cell phones are powered up, the first thing they do is look for a control channel. If a phone can't find one, it knows it cannot operate. If it finds a channel that matches their SID, it knows it's in home range. If it finds a channel but the channel doesn't match, the phone knows it's roaming. All this signal checking and identifying occurs within seconds.

Facing the Array of Choices

It is all too easy--trust me, I've been there--to be on the "wrong" plan and get hit at the end of the month with a $600 bill when you're expecting one for $70. Research pays off. You want to compare the plans and rates and minutes of different providers. You probably want to see if your local telephone company offers combination deals of local and long distance calling, internet access, and wireless service. Take the time to compare. It pays off!


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