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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  13
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.
By mentioning the study of IEEE Spectrum, the author intends to______.
选项 A、prove that the danger of using cell-phone on plane does exist
B、advocate that all airlines should provide Wi-Fi service
C、explain how cell-phone may endanger a flight
D、inform readers of which devices should be allowed to use on plane
答案A
解析 属逻辑关系题。选项B属于无关干扰，题目提到的研究出现在文章第四段，与无线网络无关，故错误。选项C答非所问，作者在文中确实讲到了移动电话给飞行带来危险的原理，但这并非作者提及题目中的研究的意义，故错误。选项D属于无中生有，文中并未列出飞行中可被使用的设备清单，故错误。作者提到这个研究的目的是为了告诉读者，在飞行过程中使用手机确实可能给飞行带来危险，因此选项A正确。
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