Which statement is true about the duration of the Power Hold feature during a trainline emergency?

Which statement is true about the duration of the Power Hold feature during a trainline emergency?

• A. It remains active until the brakes are reset.
• B. It lasts for 20 seconds.
• C. It lasts indefinitely.
• D. It lasts only while the trainline is active.

Answer: (B)

Power Hold is a safety timer tied to a trainline emergency. When the emergency is signaled, the system intentionally keeps traction power from reactivating for a short, fixed period so the brakes can engage properly and the train can begin a controlled stop. That fixed 20-second duration strikes a balance: it provides enough time for the braking sequence to settle while avoiding an unnecessarily long or indefinite loss of power. The behavior isn’t about staying active until brakes are reset or lasting indefinitely; it’s a deliberate, predictable 20-second hold that ensures consistent response across events. It’s also not just while the trainline is active, since the key feature is the predefined time window after the emergency condition occurs.

Power Hold is a safety timer tied to a trainline emergency. When the emergency is signaled, the system intentionally keeps traction power from reactivating for a short, fixed period so the brakes can engage properly and the train can begin a controlled stop. That fixed 20-second duration strikes a balance: it provides enough time for the braking sequence to settle while avoiding an unnecessarily long or indefinite loss of power. The behavior isn’t about staying active until brakes are reset or lasting indefinitely; it’s a deliberate, predictable 20-second hold that ensures consistent response across events. It’s also not just while the trainline is active, since the key feature is the predefined time window after the emergency condition occurs.