MODULAR RADIO SYSTEM – PRINCIPLE OF OPERATION
GENERAL
The Modular Radio System has standard navigation and communication
functions that include VHF-COMM, VOR/ILS/MB, DME, ADF and ATC
Transponder. Most functions are contained in the MRC.
The NIM is the interface between the radio modules and the other
components of the Modular Radio System.
Each radio module communicates to and from the NIM through separate
serial receive (RX) and transmit (TX) data bus called the Radio
Communication Bus (RCB).
The NIM supplies radio data conversion between RCB and ASCB-D in order
to supply:
• frequency, channel, code and mode control data to the radios
• NAV and status data to the avionics system
Frequency, channel and mode control of the Modular Radio System are
supplied by the Multifunction Control Display Unit (MCDU) and the Cursor
Control Device (CCD). The CCD with the PFD or the MCDU can tune,
control the modes, and show the displays for the modular radio system. The
MCDU is the primary tuning source for the modular radio system.
Radio navigation data such as VOR and ADF bearings, ILS deviations, DME
distance, etc, are distributed through the ASCB D to the MAUs and the DUs.
Pilot and copilot headset are directly connected to their relevant digital Audio
Panels; the external intercom jack is directly connected to the pilot Audio
Panel.
The cabin audio panel is interfaced with NIM 2 with an analog audio line and
with pilot Audio Panel for mode control.
The AWG function of MAU 2 provides aural warning signals to pilot and copilot
digital Audio Panels.