The marker beacon antenna receives the 75 MHz signal and sends it to a 75 MHz filter in the VOR/marker beacon (VOR/MB) receiver 1. This filter tunes and rejects unwanted signals. The output goes to a radio frequency (RF) amplifier. A detector receives the amplifier output and sends the demodulated signal to three bandpass filters.
The bandpass filters are at 400 Hz, 1300 Hz, and 3000 Hz. The filters send the signals to an audio amplifier and to an input/ output (I/O) card. The audio amplifier sends audio tones to the REU. The I/O card sends data to the DEU and the flight data acquisition unit (FDAU).
The DEU shows marker beacon data on the PFDs.