777 AIRCRAFT MAINTENANCE MANUAL
SATCOM SYSTEM -COMPONENT LOCATIONS -2
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SATCOM SYSTEM -FLIGHT DECK INTERFACE COMPONENT LOCATIONS
Flight Deck Interface Components
These components in the flight deck have interfaces with the SATCOM system:
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left, center, and right control display units (CDUs)
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Captain (CAPT), first officer (F/O), first observer (F/OBS), and second observer (S/OBS) audio control panels (ACPs).
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SATCOM SYSTEM -FLIGHT DECK INTERFACE COMPONENT LOCATIONS
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SATCOM SYSTEM -POWER INTERFACE
Left Power Management Panel
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Port beam steering unit (BSU)
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Starboard BSU
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Port low noise amplifier/diplexer (LNA/DIP)
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Starboard LNA/DIP
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LNA/DIP (for low gain antenna)
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Class A high power amplifier (HPA)
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Class C HPA
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Satellite data unit (SDU)
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Radio frequency unit (RFU).
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777 AIRCRAFT MAINTENANCE MANUAL
SATCOM SYSTEM -POWER INTERFACE
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777 AIRCRAFT MAINTENANCE MANUAL
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SATCOM SYSTEM -VOICE AND DATA TRANSMIT/RECEIVE INTERFACES
General
The SATCOM system provides a total of five voice channels and one data channel.
The control display units (CDUs) connect with the satellite data unit (SDU). The flight crew use the CDUs to control the SATCOM system.
Voice Operation
Audio control panels (ACPs) connect to the audio management unit (AMU) to control the voice signals from the flight deck to the SATCOM system.
The AMU connects with the SDU to send and receive audio signals for the flight crew.
The cabin telecommunication unit (CTU) sends passenger telephone signals through the SDU to the radio frequency unit (RFU).
Data Operation
The airplane information management system (AIMS) connects with the SDU to send and receive data signals.
The CTU connects with the RFU through the SDU to receive and transmit data signals.
EFFECTIVITY
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Signal Flow -Receive
The high gain antenna (HGA) nearest the satellite receives radio frequency (RF) signals. It sends them to the beam steering unit (BSU).
The BSU sends the signals to the low noise amplifier/diplexer (LNA/DIP).
The LNA/DIP increases the power level of the received signals. The LNA/DIP sends the amplified RF signals through the radio frequency combiner (RFC) to the radio frequency unit (RFU).
The RFU has an RF interface with the SDU to send as many as three received channels to the SDU. The RFU may also change as many as three received RF channels to digital data. It sends the data to the SDU or to the CTU through the SDU.
The SDU demodulates the received RF signals and sends them to the AMU, the facsimile machine (FAX), or the AIMS cabinet.
Signal Flow -Transmit
The AMU, AIMS, CTU or the FAX sends transmit signals to the SDU. The SDU modulates the signals from the AMU, AIMS or the FAX and sends them to the RFU. Signals from the CTU are passed through the SDU directly to the RFU.
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SATCOM SYSTEM -VOICE AND DATA TRANSMIT/RECEIVE INTERFACES
The RFU changes passenger telephone signals from the CTU to RF. The RFU modulates as many as three channels. It mixes this RF with the RF signals from the SDU. If the passenger telephone system needs more than three channels, the RFU sends digital audio to the SDU if a channel is available.
The RFU sends the RF signals through the radio frequency attenuator and the radio frequency splitter (RFS) to the high power amplifier (HPA).
The HPA increases the signal strength and sends it through the high power relay (HPR).
The HPR sends the signal to a high gain antenna system. The transmit signals received by the LNA/DIP go through the beam steering unit (BSU). The BSU electronically steers the signals to the satellite by sending them through the antenna arrays at different angles.
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