What is a key characteristic of mercury-style switches?

Mercury-style switches are known for their ability to detect changes in position or orientation, which makes them particularly suitable for applications involving fence lines. When the angle of the fence wire shifts, such as when someone tries to tamper with it or when objects come into contact with it, the mercury inside the switch moves, completing an electrical circuit. This functionality allows for effective monitoring and security along fence lines, making them a valuable tool in border patrol operations.

In contrast, other options pertain to different types of technology or applications that do not reflect the specific functionality of mercury-style switches. For instance, using these switches for recording video footage does not align with their capability for position detection. Similarly, limiting their detection capabilities to only vehicular traffic or being sensitive to sound misrepresents their primary purpose, which is more about detecting changes in physical orientation rather than sound or traffic.