Which of the following is a speed failure irregularity for the ASC apparatus?

The choice of a speed failure irregularity for the ASC apparatus is significant because it relates directly to the safety protocols that govern train operations. When the ASC (Automatic Speed Control) fails to cut in upon entering speed control territory, it indicates a critical malfunction that can jeopardize safe train operation. The ASC is designed to automatically regulate train speeds to ensure they comply with prescribed limits, especially when approaching areas that require reduced speeds, such as curves or stations.

Failure to activate the ASC when required suggests that the system is not performing its intended function, which is to prevent excessive speed and potential accidents. Recognizing this failure is crucial for maintaining safety standards on the railway. In contrast, the other options either describe normal operational scenarios or do not specifically pertain to a malfunction of the ASC system, thus making them less representative of a speed failure irregularity.