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Is using a cell phone aboard an airplane really dangerous? More and more airline companies are expanding in-flight Wi-Fi Interne

admin2015-02-12  21
问题     Is using a cell phone aboard an airplane really dangerous? More and more airline companies are expanding in-flight Wi-Fi Internet service to their entire fleet. In-flight calls, however, are still prohibited. If one can surf the Web, why can’t he use the cell?
    It operates on a totally different frequency. Cell phones transmit signals at roughly the same frequencies as aircraft communications—pilot radios and radar range from below 100 to 2,000 MHz, and many phones operate at 850 MHz or 1,900 MHz. Your cell could therefore—at least theoretically—interfere with navigation. Wi-Fi, on the other hand, signals at a higher frequency— anywhere from 2,500 to 5,000 MHz—and thus won’t get mixed up with the plane’s transmissions.
    In-flight Wi-Fi works like a moving Starbucks hot spot. The plane is rigged with three antennae— two on its belly and one on top—that receive signals from towers across the country. The frequency of those transmissions, 849 MHz, is within the range of airline communications. But they don’t interfere with the plane’s navigation, since 849 MHz is a dedicated frequency that was auctioned off and bought in 2006 by Aircell, which services American, Delta, and Virgin.
    But are cell phones on planes really that dangerous, anyway? Studies analyzing the dangers of inflight cell-phone use suggest the risks are small but real. In 2003, a study by IEEE Spectrum concluded that "continued use of portable RF-emitting devices such as cell phones will, in all likelihood, someday cause an accident by interfering with critical cockpit instruments such as GPS receivers." A study produced by the Radio Technical Commission for Aeronautics in 2006 found that portable electronic devices can interfere with airplane communications and laid out testing guidelines for airlines to figure out which devices should be permitted.
    The rationale for switching off other portable electronic devices is slightly different. Even if a device doesn’t transmit a signal—think iPods, Game Boys, "anything with an on-off switch"—it still emits energy at a frequency that could, possibly, interfere with the plane’s electronics. The Federal Aviation Administration requires all such devices to be off during takeoff and landings, but you’re allowed to turn them on once you reach a cruising altitude—presumably because any interference would be minimal and temporary. There are exceptions, though, for necessary devices like hearing aids and pacemakers.
It is indicated in Paragraph 1 and 2 that______.
选项 A、all airlines provide Wi-Fi Internet service
B、aircraft-communications’ frequency is higher than that of Wi-Fi
C、airlines provide Wi-Fi service selectively
D、not all mobile phones’ signal will interfere with navigation
答案D
解析 属信息推断题。选项A犯了夸大其词的错误，文章第一段第二句提到，越来越多的航空公司开始提供无线网络服务，但并未提及所有航空公司都会提供该服务，故错误。选项B犯了偷梁换柱的错误，将比较双方进行了调换，故错误。选项C犯了曲解文意的错误，文章第一段第二句中提到越来越多的航空公司开始在其全部的飞机上提供无线网络服务，因此并非有选择性地提供服务，故错误。第二段第三句中提到很多手机的信号频率可能会干扰飞机导航，而并非所有手机都是如此，故选项D符合题意。
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