Which items should be checked for a seal in an E-15 locomotive operating cab?

The ASC cut out valve is essential in the operation of the E-15 locomotive's air brake system. This component ensures that the Automatic Speed Control (ASC) system can be properly enabled or disabled as needed under various operating conditions. Checking for a seal on this valve is crucial because it confirms that the valve is functioning correctly and that there are no leaks that could compromise the integrity of the air brake system. A sealed ASC cut out valve helps maintain the proper operation of the speed control system and ensures that the train can maintain the necessary stopping distance, as well as respond appropriately to the engineer's commands.

In contrast, while the brake pressure gauge, equilibrium valve, and master switch are all important components of the locomotive's systems, they do not specifically have seals that indicate proper operation in the same manner as the ASC cut out valve. The gauge measures pressure, the equilibrium valve manages the distribution of air pressure, and the master switch controls power, but ensuring that the ASC cut out valve is sealed directly impacts safety and operational efficacy in relation to braking and speed control.