What response does the ATC system have if an emergency stop is necessary?

The ATC (Automatic Train Control) system is designed to ensure the safety and efficient operation of trains. When an emergency stop is necessary, the system is programmed to trigger an emergency brake application. This immediate response reduces the train's speed as quickly as possible, minimizing the risk of accidents and ensuring the safety of passengers and crew. The emergency brake application is a critical feature of the ATC system, as it allows for rapid stopping in unforeseen circumstances, such as obstacles on the tracks or signal failures.

In comparison, although sending out a distress signal, sounding an alarm system, and contacting the control center are important procedures in emergency management and communication, they do not directly address the immediate need for stopping the train in an emergency. These options would typically follow the activation of the emergency brake to inform relevant parties of the situation, but the primary action taken by the ATC system must be the emergency brake application itself to effectively halt the train's movement.