COMPONENT MAINTENANCE MANUAL
AVIATION PRODUCTS
Model FA5000
Rev. 02 Page 39
July 21/17
Description and Operation
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the restrictions on the cover page of this document.
B. Aircraft Interface (AI) PWA
The Aircraft Interface (AI) PWA mounts within the rear of the Cockpit Voice Recorder
chassis and provides the interface between the aircraft and the Cockpit Voice
Recorder’s CPU/Main Processor functions. The Aircraft Interface PWA also in-
cludes the storage power supply and provides RF filtering and lightning protection
for all input and output signals that interface with the aircraft. Input and output signal
conditioning is also provided for some signals. The Aircraft Interface PWA allows
Data Link messaging and On
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board Maintenance System (OMS) inputs in accor-
dance with ARINC 757/A specifications.
Specifically, the Aircraft Interface RF Barrier function provides RF suppression on all
input and output signals needed to meet the requirements of RTCA/DO-160F Sec-
tions 20 and 21; while it provides for lightning protection on all input and output sig-
nals needed to meet the requirements of RTCA/DO–160F Section 22.
The ARINC 757/A Aircraft Interface provides input signal conditioning for:
Audio Channel Inputs
Push-To-Test
GMT
Voice Erase
Data Link
Record
OMS
Stop Recording
The ARINC 757/A Aircraft Interface provides output signal conditioning for:
CVR Fault
Audio Out for Monitoring at the Control Unit headset.
Data Link and OMS
The Aircraft Interface also includes the storage supply portion of the power supply.
This supply conditions the applied ac or dc input power and charges the 39 Vdc stor-
age capacitor to provide the energy required to operate the Cockpit Voice Recorder
during power outages up to 200 milliseconds in duration.
C. Main Processor (MP) PWA
The Main Processor (MP) provides a data interface the Aircraft Interface (AI) . The
MP digitizes, compresses, and packages four audio channels for subsequent pro-
cessing by the MP. The MP provides interfaces with the AI for Greenwich Mean
Time (GMT) Data and Discrete Data.
The Main Processor PWA receives conditioned audio and discrete command/control
data from the AI concurrently. Audio and ARINC 429 input data are processed by
the MP and formatted into 16–bit wide words for serial Time Division Multiplexed
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