During fault isolation, which step directly follows inspecting for obvious faults?

During fault isolation, which step directly follows inspecting for obvious faults?

• A. Test individual components.
• B. Identify symptoms.
• C. Verify interlocking states.
• D. Return to service.

Answer: (C)

Fault isolation starts with confirming that the system is in a safe, known state before you dive into deeper diagnostics. After you’ve visually checked for obvious faults, the next step is to verify interlocking states. This is essential because the interlocking logic determines which routes are allowed, which signals are where, and whether protections are engaged. If the interlocking states don’t align with what you’re observing in the field, you could misinterpret symptoms or test the wrong component, potentially creating unsafe conditions or masking the real issue. Verifying the interlocking ensures you have a valid baseline and guides you to the correct diagnostic path—whether the fault lies in the interlocking itself, in wiring, or in field equipment. Only after this verification would you proceed to targeted component testing, interpret symptoms, or, once everything checks out, return to service.

Fault isolation starts with confirming that the system is in a safe, known state before you dive into deeper diagnostics. After you’ve visually checked for obvious faults, the next step is to verify interlocking states. This is essential because the interlocking logic determines which routes are allowed, which signals are where, and whether protections are engaged. If the interlocking states don’t align with what you’re observing in the field, you could misinterpret symptoms or test the wrong component, potentially creating unsafe conditions or masking the real issue. Verifying the interlocking ensures you have a valid baseline and guides you to the correct diagnostic path—whether the fault lies in the interlocking itself, in wiring, or in field equipment. Only after this verification would you proceed to targeted component testing, interpret symptoms, or, once everything checks out, return to service.