Which of the following best describes the action of the safety loop MCB when tripped?

The action of the safety loop Miniature Circuit Breaker (MCB) when tripped is best described by applying the emergency brake and signaling for maintenance. When the MCB is triggered, it indicates a fault or abnormal condition in the electrical circuit that could pose a safety risk. In such cases, the system is designed to take immediate action by applying the emergency brakes to prevent any potential accidents, thus ensuring the safety of the operation. Additionally, tripping the MCB typically signals that maintenance is required to address the fault, preventing the system from operating until the issue is resolved and safety is restored.

In contrast, preventing further train operations does not convey the immediate response—though it is a function of safety circuitry, it lacks the specifics of brake application and the signal for maintenance. Options that suggest automatic re-enabling or informing the operator of normal function are not relevant because they imply a continuation of operation rather than addressing the critical nature of a tripped safety function.