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

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  18
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.
The frequency 849MHz doesn’t interfere with the plane’s GPS system because______.
选项 A、it’s out of the range of airline communications
B、it’s like a moving Starbucks hot spot
C、it was sold to a Wi-Fi service provider
D、it’s received by the antenna on top of a plane
答案C
解析 属事实细节题。选项A属于反向干扰，与原文中提到的内容正好相反，849MHz这个频率确实是在飞机通讯频率的范围内，故错误。选项B和选项D均犯了捕风捉影的错误，利用文章确有内容捏造得来，故均错误。文章提到，2006年，这个频率被名为Aircell的公司购得，因此选项C符合题意。
转载请注明原文地址:https://kaotiyun.com/show/Os74777K
0

考研英语一

相关试题推荐
随机试题
最新回复(0)