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747-400 MAINTENANCE MANUAL
 (j)  
Altitude Alert Approach (optional)

 1)  A chord sound is generated if the Altitude Alert Approach analog input discrete is activated and the altitude alert approach aural program pin is activated. The sound is initiated one time for each activation of the altitude approach input. The characteristics of the chord sound are three equal amplitude frequency components generated simultaneously. The frequency components are 520 Hz, 640 Hz and 760 Hz and the duration of the sound is 1.5 |0.25 seconds.

 (k)  
A/P Mode

 1)  Two A/P mode change analog discrete inputs are required to activate the clicking sound. The timing logic is implemented such that if either A/P mode change input is activated, the clicking sound is generated. If the second input is activated while the initial A/P mode change input is still active, no additional clicking sound series is initiated.

 (l)  
Ground proximity and windshear warnings are indicated by a voice. The Ground Proximity Warning System is discussed in detail in AMM 34-46-00/001.

 (m)  
All of the unique aural sounds are capable of being produced with independent volume levels; i.e., the siren output differs from the bell output and both differ from the chime output, etc. In addition to having each sound controlled to a relative value with respect to other sounds, each sound volume is automatically adjusted to levels which produce high intelligibility to overcome cockpit ambient noise for various flight mode profiles. To accommodate the relative volume differences between sounds as well as to compensate for automatic volume level changes due to cockpit ambient noise, the ASC is designed to accommodate a 21 db dynamic range.

 B.  BITE test
 (1)  A 1,000 Hz sinewave test tone is generated during the power up BITE test. The test tone will be used to test the integrity of the interface between the aural output of the ASC and the aural warning cockpit speaker. The duration of the test tone does not exceed 500 ms. This tone is amplified by the aural warning cockpit speaker amplifier and returned to ASC, on the single ended speaker aural return, where it is monitored to determine the integrity of the speaker interface.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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747-400
MAINTENANCE MANUAL

 C. Engine Indicating and Crew Alerting System (EICAS)
 (1)  
The EICAS consolidates engine and subsystem indications, provides a centrally located crew alerting system, displays maintenance data and shows system status information received for the Aural Warning System. EICAS is discussed in detail in chapter 31-61-00/001.

 (2)  
Warnings are indicated by red messages at the top of the message list. Cautions appear as amber messages below the lowest warning. Advisories are also indicated by amber messages, but are indented one space so they can be distinguished from cautions. Advisories appear below the lowest caution.

 (3)
EICAS Message List (For MAWEA) ~..................................................................... | WARNING MESSAGES | ....................................................................... | SYSTEM CONDITION | EICAS MESSAGES | ....................................................................... | ANY THROTTLE AT IDLE AND BELOW 800 FEET | CONFIG GEAR | | RADIO ALTITUDE AND ANY GEAR NOT DOWN AND | | | LOCKED OR LANDING FLAPS AND ANY GEAR NOT | | | DOWN AND LOCKED. | | ....................................................................... | EITHER BODY GEAR NOT CENTERED WITH TAKEOFF | GEAR NOT CTR | | THRUST SELECTED FOR ANY ENGINE. | | ....................................................................... | LE AND TE FLAPS NOT IN TAKEOFF POSITION | CONFIG FLAPS | | FOR A TAKEOFF AND TAKEOFF THRUST | | | SELECTED ON ANY ENGINE | | ....................................................................... | SPOILERS NOT DOWN FOR A TAKEOFF AND | CONFIG SPOILERS | | TAKEOFF THRUST SELECTED ON ANY ENGINE | | ....................................................................... | STABILIZER NOT IN TAKEOFF RANGE FOR A | CONFIG STAB | | TAKEOFF AND TAKEOFF THRUST SELECTED ON | | | ANY ENGINE | | ....................................................................... | PARKING BRAKE SET AND TAKEOFF THRUST | CONFIG PARK BRK | | SELECTED ON EITHER ENGINE | | 2.............................................….......................1
　
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