The marker beacon receiver is used as part of the ILS. The marker beacon receiver is always on and detects any marker beacon signals within the reception range of the aircraft. The receiver detects the three marker tones – outer, middle, and inner – and provides the marker beacon annunciations located to the left of the Altimeter on the PFW. The Radios Button on the audio panel opens a list of annunciator buttons for the different navigation radios being monitored. The MKR Annunciation Button enables or disables the audio function of the marker beacon. The button annunciation indicates when marker beacon audio is selected.

During marker beacon audio reception, pressing the flashing MUTE Button mutes the audio but does not affect the PFW marker annunciations. The marker tone is silenced, then waits for the next marker tone. The flashing MUTE Button is also removed during audio muting. The audio returns when the next marker beacon signal is received.

Pressing the High Sense Annunciation Button in the audio panel menu switches between high and low marker beacon receiver sensitivity. The High Sense function (annunciation illuminated) is used to provide an earlier indication when nearing a marker during an approach. The Low Sense function (annunciation extinguished) results in a narrower marker dwell while over a station.