Cessna 172R Pilot Operating Handbook page 269

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Dec 2/96
S3-5
CESSNA
SECTION 9 - SUPPLEMENTS
MODEL 172R
SUPPLEMENT 3 - FAA APPROVED
AUDIO SELECT BUTTONS --
Push button audio selection is available
for three Communications receivers ("COM 1", "COM 2", and
"COM
3"), two Navigation receivers ("NAV 1" and "NAV 2"), the internal
Marker Beacon receiver ("MKR"), one DME, one ADF, and
one
additional auxiliary receiver ("AUX"). The "AUX" position could
be
used, for example, for a second DME or ADF. When
a receiver's
audio is selected, the green annunciator illuminates at the bottom
of
the button. push the button again to deselect the receiver's audio.
MICROPHONE SELECTOR SWITCH (MIC)
--
Used to select the
desired transmitter for the cockpit microphones. The "Cl ", "C2", and
"C3" positions are for transmitting on the Com 1, Com 2, and
Conn 3
communications transceivers, respectively. The "EMG" (emergency)
position is used to bypass the KMA 26's audio amplifier and directly
connects Com 1 to the pilot's microphone and headphones.
This
provides a fail-safe method of communication should the unit fail. The
"PA" position may be selected when the aircraft is configured with
a
passenger address capability.
The "Auto Com" feature always
provides automatic headphone audio selection to match the Com
transmitter in use.
To add speaker audio, simply push the Speaker
Select Switch (inner right knob) to the "in" position.
Pulling the switch
to the "out" position removes speaker audio.
SPEAKER SELECT (PUSH SPKR) SWITCH -- With the Speaker Select
Switch pushed in, both headphone and cabin speaker audio will
be
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heard. Headphone audio is active full-time. Headphone audio cannot
be deselected.
MONITOR SELECT (MONI) BUTTON -- When activated, if Com 1
is
selected on the Microphone Selector Switch then Com 2 audio
is
automatically routed to the speaker. Or if Com 2 is selected on the
Microphone Selector Switch, then Com 1 is routed to the speaker.
Pressing the "MONI" button again will disable the feature.
Initially
when "MONI" is selected the green annunciators in the button flash for
approximately 5 seconds, then remains steady while the Conn
annunciation returns to its previous state.
CREW INTERCOM VOLUME (VOL CREW) KNOB and INTERCOM VOX
SENSITIVITY SET (INTERCOM PUSH VOX) SWITCH
-- Inside knob
adjusts Pilot and Copilot intercom volume. Intercom operation is voice
activated (VOX), where intercom becomes active automatically when
a
crew member or passenger begins to speak. Set the intercom VOX
squelch by momentarily pressing and releasing the left inner knob
when no one is speaking.
Figure 1. Bendix/King KMA 26 Audio Selector Panel (Sheet 2
of 3)
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