The function of the audio integrating system is to give audio control to the pilot, the copilot, and other flight-stations (observer audio-jack panel, nose and aft-compartment service-interphone units). The audio integrating system controls the audio functions of the pilot and copilot radios (communication and navigation transmitters/receivers) and the operation of the interphone system. The system is also an interface for the supply of aircraft audio alarm messages (voice and tones). The audio integrating system uses digital audio but direct analog-audio backup is also available for emergency mode operation.

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The audio integrating system has two flight-compartment loudspeakers. One of the loudspeakers is above the pilot's seat. The second loudspeaker is above the copilot's seat.

The volume control for the pilot flight-compartment loudspeaker is on the pilot audio control panel (ACP). The volume control for the copilot flight-compartment loudspeaker is on the copilot ACP.

Note: 
All aural warnings are heard on the flight compartment loudspeakers and the headsets at the same time. The aural warnings are heard, if the speaker selector switch is set on or off. The aural warning audio level cannot be adjusted.

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The audio integrating system has two ACPs, the pilot ACP and the copilot ACP. The pilot ACP is on the pilot side panel in the flight compartment. The copilot ACP is on the copilot side panel in the flight compartment. The ACPs supply an integral audio-control to the pilot/copilot.

Post Customer Option C25-620 - There is a third ACP when the observer third audio system option is installed. The observer ACP is installed on the RH avionic rack top panel. The ACPs supply an integral audio-control to the pilot/copilot. The observer ACP supplies interphone audio control and audio system monitoring to the observer.

The ACPs let the pilot/copilot/observer control the functions that follow for the aircraft audio systems:

• Microphone selection
• Transmitter selection (pilot/copilot only)
• Audio volume control
• Voice/Identifier (ID) selection
• Emergency mode selection.

Note:
The observer ACP does not have the transmit selection function. Emergency mode selection for the third ACP is only for audio system malfunction and does not set a radio to the transmit function.

Note:
Audio Control Panel configuration depends on the installed communication system options. Refer to SB 350-23-006.

In the top row, the ACP has the transmitter selection switches that follow (typical configuration):

• COM1 (VHF 1 COM) transmitter selector
• COM2 (VHF 2 COM) transmitter selector
• COM3 (VHF 3 COM (option)) transmitter selector
• HF1 (option) transmitter selector
• HF2 (option) transmitter selector
• CAB (cabin system) selector (completion center item)
• PA (passenger address (option)) system selector.

In the second row, the ACP has the audio selector/volume control switches that follow (typical configuration):

• COM1 (VHF 1 COM) audio selector/volume control
• COM2 (VHF 2 COM) audio selector/volume control
• COM3 (VHF 3 COM (option)) audio selector/volume control
• HF1 audio selector/volume control
• HF2 (option) audio selector/volume control
• CAB (cabin system) audio selector/volume control (completion center item)
• PA (passenger address) system audio selector/volume control.

In the third row, the ACP has the audio selector/volume control switches that follow (typical configuration):

• DME1 (distance measuring equipment 1) audio selector/volume control
• DME2 (distance measuring equipment 2 (option)) audio selector/volume control
• ADF1 (automatic direction finder 1) audio selector/volume control
• ADF2 (automatic direction finder 2 (option)) audio selector/volume control
• MKR (marker) audio selector/volume control
• INPH (interphone) audio selector/volume control
• SPKR (speaker) audio selector/volume control.

In the bottom row, the ACP has the audio selector/volume control switches that follow:

• NAV1 (VHF navigation 1) audio selector/volume control
• NAV2 (VHF navigation 2) audio selector/volume control
• VOICE/BOTH/ID toggle switch
• EMER/NORM (emergency/normal) toggle switch
• O2 MASK/NORM toggle switch
• HDPH (headphone) volume control.

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The audio integrating system has two control panel electronics (CPE), the CPE No. 1 (pilot), and the CPE No. 2 (copilot). There is a third CPE when the observer third audio system option is installed. The CPE No. 1 changes the digital data received to analog data, and sends the output signal to the pilot headset and the left flight-compartment loudspeaker. The CPE No. 2 changes the digital data received to analog data, and sends the output signal to the copilot headset and the right flight-compartment loudspeaker. The CPE No. 3 (observer) changes the digital data received to analog data, and sends the output signal to the observer headset.

The CPEs get power from the 28 VDC electrical busses as follows:

• The CPE No. 1 gets power from the L ESS BUS through circuit breaker CB1-B1 on the left circuit-breaker panel, and from the R MAIN BUS through circuit breaker CB2-F4 on the right secondary power-center (RSPC).
  
  
• The CPE No. 2 gets power from the R ESS BUS through circuit breaker CB2-B1 on the right circuit-breaker panel and from the L MAIN BUS through CB1-F4 on the left secondary power-center (LSPC).
  
  
• The CPE No. 3 gets power from the R MAIN BUS through circuit breaker CB4-D3 on the RSPC.

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The audio integrating system has two radio transmit switches, the pilot radio-transmit switch and the copilot radio-transmit switch. The pilot radio-transmit switch is on the outboard handle of the pilot control wheel. The copilot radio transmit-switch is on the outboard handle of the copilot control wheel.

The radio transmit switch is a three-position switch with inboard, middle and outboard positions. The outboard position is the radio-transmit position. The inboard position is the interphone position. The middle position is the off position.

The switch is spring-loaded to go back to the middle (off) position. When set, the pilot radio-transmit switch sends a discrete signal to the CPE No. 1. When set, the copilot radio-transmit switch sends a discrete signal to the CPE No. 2.

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The audio integrating system has two radio interface-units (RIU), the RIU No. 1 and the RIU No. 2. The RIU No. 1 is in the LH equipment rack. The RIU No. 2 is in the RH equipment rack.

As the radio management unit for the aircraft system, the RIU receives audio inputs from the components and sources that follow:

• Radio sensors
• ACPs
• CPEs
• Other aircraft audio sources

The RIU changes received analog signals to digital signals. The RIU also supplies audio signals (through the CPEs) to the loudspeakers, headsets, and cockpit voice recorder (CVR).

Also, the RIU has aural warning functions that are controlled by the data concentrator unit (DCU) (The warning inputs from the traffic alert and collision-avoidance system (TCAS) and traffic surveillance system (TSS) and the terrain-avoidance warning system (TAWS) do not go to the DCU). The RIU has a non-volatile memory (NVM) that keeps the different aural warning tones and voice alarms. Each DCU channel tells its same-side RIU to supply the necessary aural warning. The DCU tells the RIU when to start and stop the warning. The DCU gives the priority of the warning and also tells the RIU if a chime is required.

The RIU No. 1 and the RIU No. 2 receive power from the right and left primary 28 V dc bus as follows:

• The L ESS BUS supplies 28 VDC power to the RIU No. 1 through circuit breaker CB1-B4
• The L ESS BUS supplies 28 VDC power to the RIU No. 1 through circuit breaker CB1-B5
• The R MAIN BUS supplies 28 VDC power to the RIU No. 2 through circuit breaker CB2-B4
• The R MAIN BUS supplies 28 VDC power to the RIU No. 2 through circuit breaker CB2-B5

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The audio integrating system has two RIU trays, the RIU tray No. 1 and the RIU tray No. 2. The RIU tray No. 1 is in the LH equipment rack. The RIU tray No. 2 is in the RH equipment rack. The RIU is installed in the RIU tray.

Two hold-down clamps on the tray engage the hold-down hooks on the RIU and attach the RIU to the tray. The RIU has a swivel-handle to help remove the RIU from the tray. The connector at the rear of the tray gives the interface between the RIU and the aircraft systems.

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The communication and navigation audio signals are supplied to the RIUs and CPEs from the pilot and copilot radios (VHF 1, VHF 2, VHF 3, HF 1, HF 2, ADF 1, ADF 2, DME 1, DME 2, NAV 1, NAV 2, and MRK). The RIUs and CPEs also receive audio from the interphone system and the aural warning system. The audio integrating system supplies switching, amplification, conversion, and isolation for the incoming audio signals. The amplification, conversion, and switching are separate for the pilot and copilot.

Audio-Integrating System Interfaces

Internal Interfaces

The audio integrating system has interfaces between its components to transmit digital data, analog audio, and discrete control signals.

Digital Data

The RIUs give and get digital data through aeronautical radio inc. (ARINC) 429 high-speed data busses to the CPEs as follows:

• The RIU No. 1 gives data on LA-RIU-3 and LB-RIU-3 busses to CPE No. 1
• The RIU No. 1 gets data on L-CPE-1 bus from the CPE No. 1
• The RIU No. 1 gives data on LA-RIU-4 and LB-RIU-4 busses to CPE No. 2
• The RIU No. 1 gets data on R-CPE-2 bus from CPE No. 2
• The RIU No. 1 gives data on LA-RIU-5 and LB-RIU-5 busses to CPE No. 3
• The RIU No. 1 gets data on C-CPE-1 bus from CPE No. 3
• The RIU No. 1 gives data on LB-RIU-14 to CPE No. 1, No. 2, and No. 3
• The RIU No. 2 gives data on RA-RIU-4 and RB-RIU-4 busses to CPE No. 1
• The RIU No. 2 gives data on RA-RIU-3 and RB-RIU-3 busses to CPE No. 2
• The RIU No. 2 gets data on R-CPE-1 bus from CPE No. 2
• The RIU No. 2 gets data on L-CPE-2 bus from the CPE No. 1
• The RIU No. 2 gives data on RA-RIU-5 and RB-RIU-5 busses to CPE No. 3
• The RIU No. 2 gets data on C-CPE-2 bus from CPE No. 3
• The RIU No. 2 gives data on RB-RIU-14 bus to the CPE No. 1, No. 2, and No. 3 (optional).

The CPE No. 1 gives and gets interphone audio to/from the CPE No. 2 and CPE No. 3 (optional). Also, each CPE sends and receives data to and from the same-side ACP, on a control bus.

Discrete Inputs/Outputs

Each RIU sends and receives to/from the other RIU a master/slave discrete signal.

The CPE No. 1 gets an emergency select discrete-signal from the ACP No. 1. The CPE No. 2 gets an emergency select discrete-signal from the ACP No 2. The CPE No. 3 gets an emergency select discrete-signal from the ACP No. 3.

Analog Audio

Analog audio to the pilot flight-compartment loudspeaker is from the CPE No. 1. Analog audio to the copilot flight-compartment loudspeaker is from the CPE No. 2.

External Interfaces

The audio integrating system has external interfaces with the pilot and copilot radios, the TAWS and TCAS/TSS systems, the DCU, the CVR, and the interphone system. For the emergency audio functions, there is a direct interface between the CPEs and the VHF communication system (emergency audio (EMER AUDIO) and push-to-talk (PTT) discrete signals).

The emergency mode is activated when the NORM/EMER toggle switch, on the ACP, is set to the EMER position. The emergency mode is also activated when power for the applicable CPE is lost.

Radios

The RIUs send tune and digital audio to each radio system on two ARINC 429 high-speed data busses.

The RIUs receive echo and digital audio from each radio system on one ARINC 429 high-speed data bus. The RIUs send/receive the data as follows:

• The RIU No. 1 gives tune data and digital microphone audio to the pilot radios. The pilot radios give echo data and digital audio to RIU No. 1.
  
  
• The RIU No. 2 gives tune data and digital microphone audio to the copilot radios. The copilot radios give echo data and digital audio to RIU No. 2.
  
  
• The RIU No. 1 gives tune data and digital microphone audio to the No. 3 VHF COM. The No. 3 VHF COM gives echo data and digital audio to RIU No. 1.

Also, the RIUs have interfaces with ARINC 429 low-speed data busses and interfaces for analog signals. These interfaces are for the satellite communication (SATCOM) system, the air traffic control (ATC) transponder system, the HF communication system, and the selective calling (SELCAL) system.

TAWS

The RIU No. 1 and No. 2 get an alert discrete signal and set analog audio from the TAWS computer.

TCAS/TSS

The RIU No. 1 and No. 2 get an alert discrete signal and set analog audio from the TCAS/TSS unit.

DCU

The RIU No. 1 gets sound warning command-data, with an ARINC high-speed data bus (A-DCU-8), from the DCU. The RIU No. 2 gets sound warning command-data, with an ARINC high-speed data bus (B-DCU-8), from the DCU. The RIU No. 2 gets a master/slave discrete signal from the RIU No. 1 (RIU No. 1 gives the warnings to RIU No. 2).

CVR

The CVR receives a summation of the headphone and microphone outputs from the CPEs on two channels.

Analog audio from CPE No. 1, CPE No. 2 and CPE No. 3 (optional) goes to the CVR.

Interphone

CPE No. 1 and CPE No. 2 send/receive audio signals and discrete signals to/from the components that follow:

• Nose service-interphone unit
• Aft-compartment service-interphone unit
• Pilot audio-jack panel
• Copilot audio-jack panel
• Maintenance panel.

The CPE No. 3 (optional) sends audio signals to the observer console panel when the observer third audio system option is installed.

The service interphone units and the audio jack panels are described in the interphone system

Audio Controls

The flight crew uses the ACP buttons for transmitter selection, audio source selection, and audio volume control.

The flight crew also uses the ACP buttons for voice/identifier, oxygen-mask microphone, emergency mode, and interphone selections.

The pilot (copilot) uses the hand microphone PTT switch or the radio transmit (R/T) switch on the pilot (copilot) control wheel to speak on the interphone (R/T switch set inboard to INPH) or to start radio transmission (R/T switch set outboard to TX).

The observer uses the ACP buttons for voice/identifier, emergency mode, and interphone selections and audio volume control. The observer ACP cannot be used for the selection of a transmitter. It can only be used for monitoring the radio system audio.

Transmitter Selection

The ACP top-row switches route the microphone audio to the applicable transmitter or PA system. The switches are interlocked (only one selection at a given time is possible). When a transmitter selection button is pushed, it automatically releases the transmitter selection button that was pushed before (the previous selection is removed). A green light comes and stays on, on the applicable button, to show the active selection.

When the COM1, COM2, COM3, HF1, or HF2 button is on (pushed in), the microphone is connected to the transmitter of the applicable radio. When the PA button is on (pushed in), the microphone is connected to the PA system.

Audio Selection/Volume Control

The audio-selection/volume-control buttons on the ACP (COM1, COM2, COM3, HF1, HF2, PA, DME1, DME2, ADF1, ADF2, MKR, NAV1 and NAV2) are push-lock switches. In the pushed in position, the audio for the applicable source is off. In the pulled out position, the output of the applicable source is sent to the headphones and loudspeakers. In the pulled out position, the button can be turned to adjust the audio volume of the applicable source.

Interphone Selection/Volume Control

Selection of the INPH control, on the ACP, enables the intercommunication (analog audio) between the crew positions in the flight compartment and service interphone positions external to the aircraft. The INPH button is a push-lock switch. When the INPH button is pulled out, it makes the related boom microphone hot on the interphone system. A PTT discrete input from the control wheel, or hand microphone, will disable INPH selection, as long as, that input is present.

The pilot/copilot/observer turns the INPH button to adjust the volume of the interphone audio.

Loudspeaker Selection/Volume Control

The SPKR button on the ACP, when pulled out, enables the applicable left or right loudspeaker. The pilot/copilot turns the SPKR button to adjust the overall volume of the loudspeaker. The SPKR controls operate in series with the individual audio source controls.

Note: 
SPKR volume control does not have an effect on the audio volume of aural warnings.

Headphone Volume Control

The pilot/copilot/observer turns the HDPH button, on the ACP, to adjust the overall volume of the applicable headphones. The HDPH controls operate in series with the individual audio source controls. Also, there is a connection for the headphones on the maintenance panel in the left equipment rack. Audio to the headset from this panel can be adjusted with a volume control button on the maintenance panel. The audio from this panel is always the same as the copilot audio.

Note: 
HDPH volume control does not have an effect on the audio volume of aural warnings.

Voice/Identifier Selection

The VOICE/ID/BOTH switch, on the ACP, is a three-position switch. In the VOICE position, only voice is heard from the NAV ADF receivers. In the identifier (ID) position, only the morse identifier code is heard. In the BOTH position, both voice and identifier code are heard.

Emergency/Normal Selection

The EMER/NORM switch is a two-position toggle switch that controls the transmission of digital and analog audio for the pilot and copilot VHF radios. In the NORM position, analog audio is converted to digital audio and then transmitted between the VHF radio and the related headphones, loudspeakers, and microphones. In the EMER position, analog audio is transmitted directly between the VHF radios and their related headphones, loudspeakers, and microphones. In the emergency mode, no digital audio from other sources (non-VHF) is transmitted to the on-side speaker. Also, in this mode, no other audio, other than aural warnings, is heard over the headphone.

Oxygen Mask Microphone Selection

The O2 MASK/NORM switch, on the ACP, is a two-position toggle switch. In the NORM position, the headphone boom microphone is the active microphone. In the O2 MASK position, the oxygen mask microphone is the active microphone.

Radio Tuning

Radio tuning can be done with the two different procedures that follow:

• Primary radio tuning, which is done with the display control panel (DCP) and the multi-function display (MFD) radio menus
• Secondary radio tuning, which is done through the control display unit (CDU).

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The audio integrating system has interfaces with the aircraft systems that follow:

• Speech Communication
• Interphone System
• Voice Recorder System
• Engine Indication and Crew Alerting System (EICAS)
• Independent Position Determining
• Dependent Position Determining

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The pilot activated test (PAT) of the aural warning function can be done with the rotary test switch on the SYSTEMS TEST control-panel set to ANNUN A or ANNUN B position. When the test switch is momentarily pushed (approximately 1 second) it starts a test for the DCU channel and its related same-side RIU.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
LS1	FLIGHT COMPARTMENT LOUDSPEAKER (LH)	ZONE(S) 211	23-51-01
LS2	FLIGHT COMPARTMENT LOUDSPEAKER (RH)	ZONE(S) 212	23-51-01
PL1	AUDIO CONTROL PANEL (ACP) (LH)	ZONE(S) 211	23-51-05
PL2	AUDIO CONTROL PANEL (ACP) (RH)	ZONE(S) 212	23-51-05
A167	CONTROL PANEL ELECTRONIC (CPE) (LH)	PANEL(S) 211FZ ZONE(S) 211	23-51-09
A168	CONTROL PANEL ELECTRONIC (CPE) (RH)	PANEL(S) 212FZ ZONE(S) 212	23-51-09
S107	RADIO TRANSMIT SWITCH (LH)	ZONE(S) 211	23-51-13
S108	RADIO TRANSMIT SWITCH (RH)	ZONE(S) 212	23-51-13
A17	RADIO INTERFACE UNIT (RIU) NO. 1	ZONE(S) 221	23-51-21
A18	RADIO INTERFACE UNIT (RIU) NO. 2	ZONE(S) 222	23-51-21
-	RADIO INTERFACE UNIT (RIU) TRAY NO. 1	ZONE(S) 221	23-51-25
-	RADIO INTERFACE UNIT (RIU) TRAY NO. 2	ZONE(S) 222	23-51-25

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