777 AIRCRAFT MAINTENANCE MANUAL
PAS -COMPONENT LOCATIONS
EFFECTIVITY BEJ ALL 23-31-00
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PAS -COMPONENT LOCATIONS 2
PAS Components
The speaker drive modules (SDM)s are in three columns down the center of the airplane.
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777 AIRCRAFT MAINTENANCE MANUAL
PAS -COMPONENT LOCATIONS 2
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PAS -POWER INTERFACES
General
Circuit breakers in two panels control power to the passenger address system.
Standby Power Management Panel
The passenger address/cabin interphone (PA/CI) controller uses two 28v dc inputs for the passenger address function. One input supplies power to the normal passenger address controller. The other supplies power to the alternate passenger address controller.
There is a circuit breaker for each column of speaker drive modules (SDMs). The ambient noise sensors (ANSs) get a positive 15v and a negative 15v from the connected SDM.
The zone management units (ZMUs) get 28v dc for the circuitry that does the direct access function.
Left Power Management Panel
The prerecorded announcement machine (PRAM) uses 115v ac.
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777 AIRCRAFT MAINTENANCE MANUAL
PAS -POWER INTERFACES
EFFECTIVITY BEJ ALL 23-31-00
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PAS -PRIORITY 1, 2A, AND 2B INTERFACES
General
The passenger address system accepts and sends announcements at these levels of priority:
*
Flight interphone (priority 1)
*
Direct access (priority 2A)
*
Cabin interphone (priority 2B)
*
Recorded announcements (priority 3A)
*
Video system audio (priority 3B)
*
Boarding music (priority 4).
Announcements from the flight crew and attendants have the three highest priority levels.
Priority 1 -Flight Interphone
The flight crew normally uses the flight interphone system to make passenger address announcements. The audio management unit (AMU) sends microphone audio and PTT to the passenger address/cabin interphone (PA/CI) controller. The PA/CI controller sends sidetone back to the AMU.
Priority 2A -Direct Access
Flight attendants normally use the cabin interphone system (CIS) to make PA announcements.
The direct access function lets attendant announcements go around the CIS circuits and connect directly to the PAS. They use direct access if there is a failure of the CIS.
Only two of the cabin attendant handsets (CAHs) have the direct access function. They are at door 1 left and door 3 left.
To make a direct access announcement, you push a direct access switch on the cabin attendant handset (CAH) cradle. This energizes a relay in the ZMU and sends the audio past the CIS circuits to the PA/CI controller.
Priority 2B -Cabin Interphone
Flight attendants normally use the CIS to make passenger address (PA) announcements. They use any CAH to make an announcement and select a PA area. The attendant dials a PA code. This connects the mic and PTT to the CIS circuits in the zone management unit (ZMU).
The flight crew also uses the cabin interphone system to make announcements in a selected area. To do this, the flight crew uses either the flight deck handset (FDH) or the flight interphone system. To use the flight interphone system, they dial the area on the center control display unit (CDU).
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777 AIRCRAFT MAINTENANCE MANUAL
PAS -PRIORITY 1, 2A, AND 2B INTERFACES
EFFECTIVITY BEJ ALL 23-31-00
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PAS -PRIORITY 3 AND 4 INTERFACES
General
These three lower priorities are for recorded announcements, video audio and boarding music.
Priority 3A -Recorded Announcements
The prerecorded announcement machine (PRAM) sends recorded announcements to the PA/CI controller. It also sends a keyline signal when a recorded announcement is in progress.
If cabin decompression occurs, the PA/CI controller sends a signal to the PRAM. This causes the PRAM to play an emergency announcement.
During a priority 1, 2A, or 2B announcement to all areas, the PA/ CI controller sends a pause signal to stop the recorded announcement.
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