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

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.

Explanation:
B: A physical IDS can employ an electromechanical or volumetric system to detect intruders. An electromechanical system is less sensitive than a volumetric
system. An electromechanical system detects a change or break in a circuit. For example, electromechanical detectors can detect movement on walls, screens,
ceilings, and floors when the fine wires embedded within the structure are broken. Or magnetic contact switches can be installed on windows and doors. If the
contacts are separated because the window or door is opened, an alarm will sound. Volumetric systems can detect changes in vibration, microwaves, ultrasonic
frequencies, infrared values, and photoelectric changes.
A is incorrect because volumetric systems are more sensitive than electromechanical systems. Also, volumetric systemsnot electromechanical systems
detect changes in subtle environmental characteristics, such as vibration and ultrasonic frequencies. Electromechanical systems work by detecting a change or
break in a circuit.
C is incorrect because the statement is backward. Electromechanical systems make use of metallic foil in windows or pressure mats to detect a change or break
in a circuit. The electrical circuits can be strips of foil embedded or connected to windows. If the window breaks, the foil strip breaks, which sounds an alarm. A
pressure pad is another type of electromechanical detector. It is placed underneath a rug or portion of the carpet and is activated after hours. If someone steps on
the pad, an alarm activates because no one is supposed to be in the area during this time. Volumetric systems deal with environmental changes, such as
ultrasonic frequencies, but also vibration, microwaves, infrared values, and photoelectric changes.
D is incorrect because volumetric systems are more sensitive, the reason being that they detect subtle changes in environmental characteristics.
Electromechanical systems are less sensitive and work by detecting a change or break in a circuit.