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 E.  The functions of the aural warning system are to determine the existence of abnormal conditions through logic circuits and to generate audible signals, both those for warning purposes and those for gaining attention to a call.
 F.  The aural warning system consists of printed circuit cards housed in the Modularized Avoinics and Warning Electronics Assembly (MAWEA), located in front of the E/E racks on the right half of the airplane on the left side wall. Sensors for the various systems feed signals to the the PC cards through interconnecting wiring. The Master and Caution lights, greenband indicating lights, display of EICAS messages provide visual displays. Shaking of the control column (stick shaker), and the aural warning speakers, providing an aural warning, complete the system.
 G.  Primary operating power for the aural warning system is supplied by the STANDBY BUS No. 3 and the F/O INST BUS through the MAWEA PWR circuit breakers (A & B) on the P7 overhead circuit breaker panel.
 2.  Printed-Circuit Cards_____________________
 A.  There are four types of printed-circuit cards housed in the MAWEA card file. Three type are used for the aural warning system, they are Universal Logic Cards (ULC), Signal Collection/Tail ID Cards (SCID), Aural Synthesizer Cards (ASC). The other type of card is the Digital Flight Data Acquisition Card (DFDAC).
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MAINTENANCE MANUAL

MAWEA MONITOR MASTER MONITORPANEL
CREW ALERTING CARD B (ULC) CARD (ULC)
RIGHT AURAL LEFT AURAL
SYNTHESIZER SYNTHESIZER
CARD CARD
INPUT/OUTPUT
CONNECTOR

MASTER MONITOR CARD A (ULC)
POWER SUPPLY B (INSIDE) (REF)
POWER ELECTROSTATIC
SUPPLY A JACK
(INSIDE) (IN CORNER)
(REF)
CONFIGURATION
WARNING
CARD (ULC)

MODULARIZED AVIONICS WARNING ELECTRONICS ASSEMBLY (MAWEA)
Aural Warning Printed Circuit Cards Location
Figure 1

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MAINTENANCE MANUAL

 B.  The Universal Logic Card is configured into four different modules. They are the Master Monitor A and B, Crew Alerting, Configuration and Stall Warning modules.
 (1)  
The Master Monitor Modules A and B receive inputs and control activation/reset of warning functions for takeoff/landing configuration, overspeed, autopilot disconnect, fire, windshear, GPWS and cabin pressure (Fig. 2).

 (2)  
The Crew Alerting Module receives inputs for the altitude alert, flight crew chime alert, decision height alert (optional), passenger awareness, main entry doors indication (optional), cabin pressure monitoring and passenger address volume and ASC gain control (Fig. 3).

 (3)  
The Configuration Module receives function inputs for greenband position indicating, takeoff warning, landing warning, speed brake alert, glideslope antenna switching and cabin pressure warning (Fig 4).

 C.  The Aural Synthesizer Card receives all aural inputs from the Master Monitor cards. It directs its outputs to the other ASC and to the flight compartment speakers. The aural sounds produced are warning siren, wailer (optional), clacker (optional), fire bell, caution aural (OWL), chimes, DH aural, chord and test tone. The windshear and ground proximity warning are amplified only. The ASC also automatically controls speaker gain and tests the speaker at power-up (Fig. 5).
 D.  The aural synthesizer card also amplifies the warning aurals from the TCAS.
 E.  All of the MAWEA cards are microprocessor controlled and have one red LED for displaying faults within the card, one yellow LED for interface faults and one pair of monitor jacks for monitoring the ARINC 429 output bus.
 3.  Power Supplies
______________
 A.  There are two Power Supply Units which provide +5.7 and |12.7 volts dc to each of the Aural Warning cards in the MAWEA chassis.
 B.  In the event of a power supply failure, a fail discrete is sent from the failed power supply to the MAWEA monitor panel. This discrete turns on one of the two red LEDs on the MAWEA monitor panel indicating this condition. The dc input voltages can be monitored through the monitor jacks on the MAWEA monitor panel.
　
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