Which fuse designation corresponds to the description: Low air pressure alarm stick relay?

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

Answer: (B)

Understanding fuse designations in signaling means reading them as a combination of function and device type. When the description specifies a low air pressure alarm implemented as a relay, the designation must name both the alarm function and the relay type. So the correct designation is the one that says “low air pressure alarm stick relay,” which identifies the exact component: a relay (stick relay) that provides the low air pressure alarm. The other options don’t fit because they describe a push button (instead of a relay), a different relay type (approach locking stick relay), or a system-level item (automatic train operation system) rather than the specific relay for the low air pressure alarm.