Textron Cessna 172R, Pilot Operating Handbook

Page: 486 / 500

SECTION 9
-
SUPPLEMENTS
SUPPLEMENT
20
-
FAA APPROVED
CESSNA
MODEL 172R
3. RECEIVE AUDIO
SELECT BUTTONS -
Push button audio
selection is
available
for two
Communications
receivers
(“COM 1",
“COM
2“), two
Navigation receivers (“NAV 1" and
"NAV 2“), the internal Marker
Beacon receiver ("MKR"), one
DME,
one
ADF, one additional auxiliary
receiver ("AUX") and
a speaker amplifier (“SPR"). 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
side of the button. Push the button
again
to
deselect the receiver's
audio. These buttons
are
“latched*
type
switches. When one of these
buttons
is pressed, it will
stay
in the "in“ position until the button is
pressed again and it will be
put
in the
“out"
position and removes
that
receiver from the audio. To provide
additional feedback for
button
operation, activate the key
"click"
by
pushing and holding both COM
1
and COM 2 receiver buttons
for five seconds, and release. Repeat to
defeat the dick.
4.
MICROPHONE SELECTOR SWITCH (MIC)
-
Used to select the
desired transmitter for the cockpit microphones. The
“COM
1“,
“COM
2“, and
“COM
3" positions are for transmitting
on
the Com 1, Com 2,
and Com
3
communications transceivers, respectively.
When
the mic
selector switch is
in
the
COM
1
position, both pilot
and
copilot will be
connected
to the
COM
1
transceiver. Only the person who
presses
their Push-to-Talk (PTT) switch, will be heard
over
the aircraft radio.
Turning the
rotary
switch to the COM 2
position will place pilot
and
copilot
on COM
2. The KMA 28 gives
priority
to the pilot’s PTT. If the
copilot is transmitting, and the pilot presses his PTT, the pilot's
microphone will be heard over the selected COM transmitter. Turning
the mic selector counterclockwise
to
COM
3
places both the pilot and
copilot on COM
3.
Com
3
receiver audio is automatically placed in the
headset (and speaker if selected). COM 1 and/or COM 2 receiver
audio can be selected
to
monitor those transceivers. Audio from the
selected transceiver is automatically
heard in the headsets. This
function can be checked by switching from COM 1 to COM 2 and
watching the selected audio light
on
the selector change from COM 1
to COM 2. This
ensures
the pilot will always hear the audio from the
transceiver
he
is transmitting
on.
When transmitting,
the COM
1
or
COM 2
LED audio selector will blink as a further indication of the
selected transmitter. When switching the mic selector switch from
COM 1 to COM 2, if the COM 1 audio has
been
selected,
COM
1 audio
will continue
to be heard. When
switching from COM
1 to
COM
2
if
COM
1 has
NOT been selected, COM
1
audio will be switched off.
Figure 1
.
Bendix/King KMA
28
Audio Selector Panel (Sheet
2 of 5)
S20-6
Dec
30/00
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