Which control is responsible for actuating an emergency brake application?

The master controller is designed to facilitate the operation of the train, including controlling the power and braking systems. When it comes to emergency situations, while the master controller can initiate actions that contribute to the overall braking of the train, it is specifically responsible for managing the acceleration and power settings rather than directly actuating the emergency brake application.

In emergency situations, the primary component responsible for initiating an emergency brake application is the emergency brake valve. This valve is specifically designed for that purpose to quickly stop the train. The handbrake lever is used in a stationary context to secure the train when it is parked, rather than for emergency braking while in motion. A pressure gauge merely provides information about the system's status and does not play an active role in the actuation of the emergency brake.

Understanding the distinct purposes of these components helps clarify why the correct answer relates to the control mechanism utilized for emergency braking.