What is the normal reading for the red hand on the duplex air gauge?

The normal reading for the red hand on the duplex air gauge is 0 lbs. The duplex air gauge is used to indicate the pressure in the air brake system of a train. The red hand typically serves as a warning indicator for low air pressure, showing the minimum acceptable level necessary for safe operation. A reading of 0 lbs indicates that there is no pressure available in the system, which signifies a critical state where the brakes may not function properly.

Understanding this context is crucial for train operators, as air pressure is vital for the operation of train brakes. Regular checks of the gauge ensure that the air pressure is within a safe range to maintain proper braking capabilities. The other potential readings, such as 10 lbs, 5 lbs, or 15 lbs, are not indicative of the normal state but rather would suggest varying levels of pressure that could correspond to specific operational thresholds or alerts, rather than indicating a safe or normal condition.