What action does a switch take when it is thrown?

When a switch is thrown, it allows trains to change tracks by moving the switch points to guide the train wheels from one track to another. This is a crucial function in rail operations, as it enables the movement of trains between different tracks in a yard or junction, facilitating efficient routing and the management of rail traffic.

To further clarify the context of why this is the correct action: a functioning switch is vital for operational flexibility and safety in railway systems. When the switch points are aligned properly, trains can smoothly transition from one track to another without derailing or encountering other obstacles. This controlled maneuvering is key to maintaining the schedule and flow of train operations.

Other options, while related to railway operations, do not accurately depict the action executed by a switch. For instance, automatic resetting is not a function of a thrown switch; rather, maintaining proper alignment is essential. Locking the tracks is a separate action that may occur after the switch is set, but it doesn't happen with the initial act of throwing the switch. Lastly, signaling to stop all incoming trains is an operational procedure that does not directly involve the function of switches, which focus on track transitions rather than signaling commands.