How does a train engineer change the operating mode from MATC to MCS?

The correct procedure for a train engineer to change the operating mode from MATC (Moving Automatic Train Control) to MCS (Manual Control System) involves turning the master controller and adjusting the ATC Mode switch. This action directly engages the necessary controls that facilitate the transition between the two operating modes.

In this context, adjusting the ATC Mode switch is critical, as it specifically alters the system's operational parameters, allowing the engineer to switch from automatic train control to a manual operation where they have more direct input into the train's handling. The master controller serves as the primary interface through which the engineer can manage various functions of the train, including speed and power settings.

The other options do not address the specific actions required to change the operating mode effectively or are inappropriate actions for this situation. For instance, pulling the emergency brake would abruptly halt the train but would not facilitate a mode change. Stopping the train might be necessary before changing modes, but it does not illustrate the correct method to change from MATC to MCS, which is achieved through the switch adjustments while the system is in operation. Activating the train's alarm system also does not contribute to changing the operational mode; instead, it is typically used in response to emergencies or system faults.