Which system modulates a signal to identify which beacon the aircraft is currently flying over?

The correct answer centers on the function of the Marker Beacon in aviation navigation systems. Marker Beacons are specialized radio beacons used in conjunction with instrument landing systems (ILS) to provide specific location information to aircraft. When an aircraft flies over a Marker Beacon, it receives a signal that indicates its position relative to the beacon, which is particularly useful during approach and landing phases of flight.

The Marker Beacon allows pilots to identify critical points along the approach path, such as the Outer Marker, Middle Marker, or Inner Marker, each signaling different distances from the runway, which helps in determining the aircraft's exact location as it descends. This capability is essential for precision landings in low-visibility conditions and enhances situational awareness for the pilots.

When considering the other options, while VHF Omnidirectional Range (VOR) provides navigation information and the Automatic Direction Finder (ADF) assists in determining an aircraft's direction to a radio station, neither specifically modulates a signal to identify the precise beacon being flown over like the Marker Beacon does. The Aircraft VHF Navigation System encompasses a broader range of navigation functions but also does not directly modulate signals for beacon identification in the same specific manner. Therefore, the Marker Beacon stands out for its unique role in pinpoint