What type of signals are used in connection with manually operated switches?

The correct answer is related to the type of signals specifically designed for manual switch operations, which highlights the need for effective communication between the train operator and the crew involved in switching operations. Pot signals, a form of visual signal, are employed effectively at locations like switching points where manual operation is present.

These signals typically provide clear indications of the switch's position and state, ensuring safety and coordination among the crew. Their design supports the unique requirements of railroad operations, particularly in environments where manual intervention is essential.

Other types of signals mentioned, such as call signals, semaphore signals, and signal flags, do play a role in railway communications but serve different purposes. For example, semaphore signals are more commonly associated with automatic signaling systems that convey information about train movement on tracks rather than specifically for the operation of switches. Call signals can operate in a similar context but do not specifically pertain to the manual control of switches in the way pot signals do. Signal flags also communicate information but are not typically used in modern railroad operations, particularly in automated frameworks. Understanding this distinction clarifies why pot signals are specifically relevant in the context of manually operated switches.