A pathway shall be designated Class B when it lacks a redundant path and operational capability stops at a single open; and operation is maintained during a single ground fault. Which class is this?

A pathway shall be designated Class B when it lacks a redundant path and operational capability stops at a single open; and operation is maintained during a single ground fault. Which class is this?

• A. A
• B. B
• C. C
• D. D

Answer: (B)

This question is about how wiring classifications describe fault tolerance for signaling paths. A Class B path has no redundant path, so if a conductor opens somewhere in the loop, the system’s operational capability stops at that point and downstream devices lose signaling. At the same time, it is designed to keep functioning during a single ground fault, because the fault doesn’t break the circuit path and the remaining conductors can still carry the signaling. So the described behavior—no extra path to back up the circuit, loss of operation on a single open, but continued operation during a single ground fault—matches the Class B designation. Other classes involve different levels of redundancy and fault tolerance (for example, paths with a redundant route), which is not what’s described here.

This question is about how wiring classifications describe fault tolerance for signaling paths. A Class B path has no redundant path, so if a conductor opens somewhere in the loop, the system’s operational capability stops at that point and downstream devices lose signaling. At the same time, it is designed to keep functioning during a single ground fault, because the fault doesn’t break the circuit path and the remaining conductors can still carry the signaling. So the described behavior—no extra path to back up the circuit, loss of operation on a single open, but continued operation during a single ground fault—matches the Class B designation. Other classes involve different levels of redundancy and fault tolerance (for example, paths with a redundant route), which is not what’s described here.