Which ILS marker emits the highest aural frequency?

The inner marker emits the highest aural frequency among the different types of ILS markers. Specifically, the inner marker, used in precision approaches, transmits at a frequency of approximately 3000 Hz. This distinctive sound serves as an important indicator to pilots, signaling that they are on the final approach segment of a precision approach, usually at or very near the decision height.

In contrast, other ILS markers operate at lower frequencies. The outer marker typically emits at approximately 400 Hz, while the middle marker transmits at about 1300 Hz. The locator marker, associated with the approach but not part of the ILS itself, operates at a frequency of about 1000 Hz. The differentiation in frequencies not only provides clear auditory cues but also assists pilots in understanding their position in relation to the runway during the approach phase.