COMMUNICATIONS, AUDIO INTEGRATING
Description
Aircraft Operations Manual
4/1.1
PAGE
1
1.
GENERAL
The audio integrating system provides the pilots
with intercom and audio control.
The VHF COM, HF COM and UHF COM (if
installed) systems, as well as audio signals from the
radio navigation systems, are together with the
cockpit and ground crew interconnected with the
audio integrating system. The audio integrating sys-
tem will then provide the pilot with a corresponding
number of audio channels, which can easily be se-
lected and controlled by any of the two Audio Con-
trol Panels. The communication and the audio sig-
nals are listened to and spoken with by either
headsets or cockpit loudspeakers and hand micro-
phones.
All communication is recorded by the CVR (Cockpit
Voice Recorder). The Press To Transmit signals for
the COM’s are recorded by the Flight data recorder.
2.
MAIN COMPONENTS AND SUBSYSTEMS
2.1
Remote Electronic Unit (REU)
The Remote Electronic Unit, REU, which forms the
central part of the audio integrating system, serves
as a distribution and switching center for the sys-
tems that are interconnected with the REU.
For communication, two pilot jack panels provide
connections of the headsets to the REU. There are
also two loudspeakers and hand microphones con-
nected to the REU for backup.
The REU contains two identical circuit boards pow-
ered through their associated Audio Control Panel,
ACP, by L and R BAT BUS. The circuit boards per-
form switching and amplification as selected on the
ACP of cockpit intercom, HF and VHF COM audio
and of audio idents for VOR, ILS, MARKER, DME
and ADF.
Aural warning, GPWS and PA chime signals have
fixed audio levels and can be heard regardless of
volume setting.
If one or both circuit boards should fail, the VHF
COM’s can be bypassed the REU and switched
directly to the headsets by the NORM/EMER switch
on associated ACP; VHF COM 1 to the L/P ACP
and VHF COM 2 to the R/P ACP.
2.2
Audio Control Panel (ACP)
Two ACP’s are installed in the cockpit, one for each
pilot. The ACP’s are furnished with slide levers for
volume control and a number of pushbuttons and
switches that allow various controls of the audio
system. The selected volume levels and switch set-
tings are converted into digital data and sent to the
REU for control of the systems interconnected with
the REU.
2.3
Loudspeakers
Two loudspeakers are installed in the cockpit above
each pilot’s head. The volume of the speakers are
controlled by associated SPKR slide levers, L
speaker L ACP and R speaker R ACP. Aural warn-
ing, GPWS, and PA chime signals have fixed audio
levels and can be heard regardless of volume set-
ting.
2.4
Pilot jack panel
Two pilot jack panels provide connections of the
headsets to the REU, two kinds of standard head-
set connectors are accepted; PJ
−
055B earphone
and PJ
−
068 microphone or CANNON XLR type
connectors. With Mod. No. 3144 installed, it is also
possible to connect headsets with active noise re-
duction.
For oxygen mask use, a separate jack connects the
mask microphone to the REU by the BOOM/MASK
switch on associated ACP; L mask L ACP and R
mask R ACP. PA calls with the mask microphone
can be made by pressing the PA button on the jack
panel, also see AOM 4/4.1 and 4/4.2.
2.5
Observers jack panel
The observers jack panel provides connection of
the observers headset to the REU. The same type
of connectors are accepted as for pilot jack panel. A
MIC switch provides on/off function of the observers
microphone. There is also a PHONE switch which
allows the observer to listen to either the left or the
right pilot’s communication.
From a/c 180
−
up a microphone jack is provided for
the observers oxygen mask microphone, see Fig. 6.
The jack is in parallel with the observers jack panel
Jun 01/20
