81 lines
4.8 KiB
Plaintext
81 lines
4.8 KiB
Plaintext
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Mobile Phones
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Radio phones have been around for a while. The first mobile telephone
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call was made September 11, 1946 between a Houston Post and a St. Louis Globe
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reporter. An old mobile phone service in New York city had 700 subscribers,
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but could only handle 12 conversations at a time (because it had 12 channels).
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There are some 160,000 mobile telephones nationwide.
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The old service was doomed to fail. Each major city had one or two
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powerful transmitters to communicate with all car phones in a 30- to 50-mile
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radius. To make a call from a car, you must find a vacant channel, then call
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the operator and supply the number you want to call. The operator dials the
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number and connects you when the party answers. Only a few companies have dial
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it yourself service. If someone wants to call you, they must first find the
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mobile phone operator in your area. The operator finds a vacant channel and
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transmits a series of tones that correspond to your phone and make it ring-sort
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of as if it were a pager. Once you answer, the operator connects you and the
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caller.
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Clearly, the system was slow. Worse, it could only serve a few users at a
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time. During rush hour, there was little hope of making a call. Few channels
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could be added because of the dearth of frequencies for that kind of operation.
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So now you can't get a mobile phone of this type unless someone else gives one
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up.
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Enter the cellular mobile radio. Instead of only 1 or 2 transmitters, an
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area is divided up into many small sections, called 'cells'. Wach has it's own
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low-powered transmitter just strong enough to serve it's cell. An average cell
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covers from one to eight square miles and varies in shape from a circle to a
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squashed football. Each cell touches another, some overlap slightly.
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Adjacent cells use different channels-there are more than 600 in each city
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to choose from-and a channel may be reused several times in the city if the
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cells are located far enough apart. All of the cells' transmitters hook into
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one network switching office, much like a central office handles calls form lan
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d-based telephones.
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Each transmitter constantly sends out a special signal, and as you drive
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from cell to cell, your telephone automaticly tunes in the strongest cell. When
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a call comes in for you, the network switching office uses the channel to send
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a digital pulse signal that corresponds to your ten-digit phone number (NPA+7 d
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igits).
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When the phone hears it's number, it in effect says 'Here I am, in this
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certain cell'. That information is sent back to the network switching office,
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which scans vacant frequencies, and relays the information to your cell.
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Finally, your unit tunes to that voice channel, and the cell site rings you,
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and you talk.
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It sounds complicated-and it is. But it works in seconds. And it can be
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expanded. As more and more phones are added, cells can be split into smaller
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cells with less power. Cellular radio allready exists in Japan, Denmark,
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Norway, and Sweden. In Denmark, service began in 1981 and grew to 100,000
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customers almost overnight. Within a few years all of Scandinavia will have
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compatable cellular systems. Australia, Canada, and Mexico also plan systems.
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Why has the U.S. lagged behind? Yep, it's our old freinds, the FCC. They
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studied the system for 12 years before okaying the service in 1982. The U.S.
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may be fullt celled by 1988. Now is the time to rent your backyard as a
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cellular station!
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The Bell companies will operate cellular service as the Cellular Service
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Company. Others such as GTE and MCI plan similar service. Even the Washington
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Post is trying to get into it. There are allready two systems, one in
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Washington/Baltimore, and one in Chicago. Chicago users pay about $50 rent and
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$25 monthly use fee for 120 minutes, and 25 cents/minute hereafter. Average
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bills are $150/month.
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The main unit mounts in the trunk, and just the handset sits up front. The
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antennas are very small-about nine inches-and are hidden inside the car.
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Now freaking old car phone systems shoudln't be that hard if you really
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try. The following are the freq's to remember:
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158.07-158.49 MHz (mobile)
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152.81-153.03 MHz (base stations)
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You CAN listen in on these freq's. What I'm not sure about is whether you can
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place a call --I would think so. So Freq out!
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COMMING SOON: Repair trucks, installers, and linesmen, Marine Radio, and
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Airplane phones
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==============================================================================
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[ Infinity-Cartel Network ]
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[ The Cartel Adventure/AE/Hack BBS 5.5 meg --- 206-825-6236, or 206-939-6162 ]
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[ Infinity's Edge Adventure/AE/Cat/Hack 10 meg BBS ------------ 805-683-2725 ]
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==============================================================================
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