2. 计算机
  3. IDSs can detect intruders by employing electromechanical systems or volumetric systems. Which of the following correctly describ

IDSs can detect intruders by employing electromechanical systems or volumetric systems. Which of the following correctly describ

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问题 IDSs can detect intruders by employing electromechanical systems or volumetric systems. Which of the following correctly describes these systems?
选项 A、Because they detect changes in subtle environmental characteristics, electromechanical systems are more sensitive than volumetric.
B、Electromechanical systems are less sensitive than volumetric systems, which detect subtle changes in environmental characteristics.
C、Electromagnetic systems deal with environmental changes such as ultrasonic frequencies, while volumetric systems can employ pressure mats or metallic foil in windows.
D、Electromagnetic systems are more sensitive because they detect a change or break in a circuit, while volumetric systems detect environmental changes.
答案B
解析 B正确。物理入侵检测系统(intrusion detection system，IDS)可以配置一个机电(electromechanical)系统或容积(volumetric)系统进行入侵检测。机电系统不如容积系统敏感。机电系统检测的是电路中的变更和断开。例如，机电探测器可以在嵌在墙壁、屏风、天花板和地板内的电线被破坏时，检测出它们的移动。或者可以在门或窗户上安装门磁开关。当门或窗户打开而导致磁联开关分开时，警报就会响起。容积系统能够检测出振动、微波、超声波频率、红外线值和光电的变化。
A不正确。因为容积系统比机电系统要敏感。同样，能检测细微环境特点中的变化，如振动和超声波频率的是容积系统而不是光电系统。机电系统的工作原理是检测电路中的变更和断开。
C不正确。因为这个答案说反了。机电系统利用窗户上的金属片或压力垫来检测电路中的变更或断开。该电路可以是嵌入或连接着窗户的数条金属片。当窗户被撞开，金属条断开，警报声就会响起。压力垫是另一种机电探测器。它放置在地毯或地毯的一角下，数小时后被激活。一旦有人踩到垫上，便会响起警报声，因为在这个时段内本不应该有人出现在这个区域。容积系统处理如超声波频率这样的环境变化，同样也检测诸如振动、微波、红外线值和光电变化等。
D不正确。因为容积系统更加敏感，原因是它们可以检测环境特点中所发生的细微变化。机电系统不如它敏感，只检测电路中的变更或断开。
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