Which fuse designation corresponds to the description: Low air pressure alarm push button?

• A. Low air pressure alarm stick relay.
• B. Approach locking stick relay.
• C. Automatic train operation system.
• D. Low air pressure alarm push button.

Answer: (D)

When fuse designations are chosen, they usually name the device by its function. A device described as a push button that gives a low air pressure alarm is labeled with that exact function so its purpose is immediately clear to maintenance and operators. Therefore the designation should be “Low air pressure alarm push button” because it directly and unambiguously identifies the component and its role in the system.

The other options refer to different components or subsystems (a stick relay, an approach locking stick relay, or an entire automatic train operation system) and do not describe a push button used for a low air pressure alarm, so they don’t match the description.