What component controls the train's propulsion system?

The master control handle plays a crucial role in controlling the train's propulsion system. It serves as the primary interface for the train operator to manage the acceleration and deceleration of the train. When the operator adjusts the master control handle, it sends signals to the propulsion system to increase or decrease speed accordingly. This direct control is essential for the safe and efficient operation of the train, as it allows the operator to respond to operational needs, track conditions, and safety protocols.

Other components mentioned in the question have specific functions that do not primarily control propulsion. For example, the relay switch is important for electrical control but does not directly manage speed. The throttle control may seem related to speed management, but in many systems, this function is integrated into the master control. The auxiliary brake system is designed for additional stopping power and safety but does not contribute to propulsion. Understanding the distinct roles of each component is crucial for effective train operation.