What type of signal is directly controlled by an operator?

The type of signal that is directly controlled by an operator is a controlled signal. Controlled signals are manually operated and require the intervention of a dispatcher or a signalman to change their aspects, which can include aspects like stop, proceed, or caution. These signals are essential for controlling train movements in a specific area, ensuring that the trains operate safely and in accordance with the schedules and conditions of the railway network.

In the context of train operations, controlled signals are crucial for managing complex junctions or areas where more than one train might be operating at the same time. Operators can alter these signals in real-time based on the current traffic conditions, maintenance activities, or emergencies, allowing for a flexible and responsive approach to train management.

The other signal types do not require direct human intervention to operate; they function based on the conditions of the railway environment or automated systems, making them less responsive to immediate operational changes as compared to controlled signals.