What happens when a safety system is fail-safe and a fault occurs?

• A. The system continues normal operation
• B. The system reports the fault and attempts service
• C. The system restarts automatically
• D. The system moves to a safe condition

Answer: (D)

When a safety system is fail-safe, faults trigger a transition to a safe state rather than allowing continued operation. The whole purpose is to minimize risk when something goes wrong. So the system moving to a safe condition is the expected and optimal response after a fault, ensuring hazards are mitigated (for example, shutting down power, isolating a subsystem, or placing actuators in a safe position). The other behaviors describe fault reporting or attempts to continue operation, but they don’t inherently guarantee safety in the presence of a fault.