All inputs to the receiver go through a high intensity radiated frequency (HIRF) filter. This filter provides protection to internal circuits.
Tune inputs from the NAV control panel go to the main processor. The processor sends the tune frequency to the frequency synthesizer circuits. The frequency synthesizer circuits tune the localizer receiver and glideslope receiver.
The receiver circuits send the RF signal inputs from the
antennas to the main processor. The processor computes
localizer deviation and glideslope deviation.
ILS data goes out on two ARINC 429 buses.
Output 1 goes to FCC A and FCC B.
Output 2 goes to these LRUs:
· FDAU
· Standby attitude indicator
· GPWC
· FMC
· DEUs.
The A/D function of the receiver converts the audio from the localizer ground station from an analog to a digital format. The audio then goes to the main processor. The main processor sends the audio to the REU. The processor also detects any morse code station identifier and sends it out on the data buses. When there is a station identifier on the data bus, the DEUs replace the frequency display with the four letter station identifier.