Flight Interphone System Component Location 5C8
23-52-01 Figure 1 Jun 20/88
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
C. Microphone Inputs
(1) An input is wired from each flight crewmembers boom, mask or hand mike to the remote electronics unit. Additional inputs are connected from the service interphone system, and from the external power panel.
D. Audio Outputs
(1)
Audio outputs from the remote electronics unit are provided to each flight crew station and to the external power panel. One output is for the boom microphone/headsets and one output is for the headphone jacks.
(2)
Two audio outputs are used to drive the amplifiers in the pilots' overhead speakers.
(3)
An audio output is provided to the No. 1 input of the PA amplifier when a pilot has selected PA and keys his boom/mike headset.
(4)
Amplifiers in the remote electronics unit provide the drive for the audio outputs. There are two audio amplifiers in the remote electronics unit; one used with the flight interphone and one used with the service interphone. External volume control adjustments are installed for each of the amplifiers.
E. Muting
(1) The pilot overhead speaker is muted whenever a microphone is keyed from the same pilot position (left or right) except when the pilot audio selector panel BOOM/MASK switch is in the MASK position.
F. Synthesized Audio
(1) A two wire input is provided to receive the audio warning message from the ground proximity warning system.
G. Selection
(1)
Each flight crewman selects the audio he desires to hear with that crew station audio selector panel. A push-on/push-off knob is available for each selectable audio signal. Rotation of the knob controls volume. Whatever audio selection is chosen, at the crew station audio selector panel, will be heard over the headphones and overhead speaker at that crew station.
(2)
Selection of which system will receive the microphone input from each flight crew station is made at the crew station audio selector panel. The MIC SELECTOR push button which is depressed will determine the communication system to be keyed by a PTT switch at that flight crew station. Only one MIC SELECTOR may be pressed. Pressing another selection will cancel any previous selection. The MIC SELECTOR, when depressed, will also connect the receiver audio, for that communications system, to the headphone of the flight crewman making the selection.
(3)
All audio warning messages from ground proximity and altitude alert are heard by all flight crew members without being selected on the audio selector panel.
5C8
Jun 20/88 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 23-52-01 Page 3
Digital Audio Control System Diagram 5C8
23-52-01 Figure 2 Jun 20/88
Page 4
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
4. Interphone Speakers
A. Cockpit speakers are installed in the flight compartment ceiling over the captain's and first officer's seats. Each unit contains a speaker. The volume control for each speaker is located on the audio selector panel for the corresponding pilot position. The speaker above either pilot is muted whenever that pilot's microphone is keyed except no muting occurs when that pilot's BOOM/MASK switch on the audio selector panel is positioned to the MASK position.
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