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Audio Panel Operation
KMA 29 Audio Panel Pilot’s Guide
munication capability regardless of the condition of the unit. Any time
power is removed or turned off, the audio selector is placed in the EMG
In the EMG mode, one or two of the unswitched audio inputs are sup-
plied to the pilot headset. Also, in the EMG mode, audio signals are pre-
sent in only one ear of a stereo headset.
MARKER BEACON OPERATION
The marker beacon receiver uses visual and audio indicators to alert
the crew when the aircraft passes over a 75 MHz transmitter. There is a
service adjustment located on the unit for ground maintenance to adjust
the marker audio volume level.
The outer, middle and inner marker indications are shown on an exter-
nal display. The audio panel supplies a 400-Hz “dash” audio tone for the
outer marker. The outer marker tone is keyed at a rate of two
tones/flashes per second when the aircraft is in the range of the outer
marker beacon. The panel provides a 1300-Hz tone for the middle
marker, which is keyed alternately with short “dot” and long “dash”
bursts at 95 combinations per minute. The audio panel supplies a 3000-
Hz “dot” tone for the inner marker. The inner marker tone is keyed at a
rate of six times per second.
The MKR SENS button is used to set the receiver sensitivity and to test
the marker beacon. Use high (HI) sensitivity initially. This allows you to
hear the outer marker beacon about a mile out. Then push the MKR
SENS button to switch into the low (LO) sensitivity mode. Low sensitivi-
ty gives you a more accurate location of the marker. Many pilots choose
to leave the button in the low sensitivity mode.
Pressing and releasing the MKR MUTE/TEST button causes the mark-
er audio to mute for that beacon. The muting continues until one of the
following events occurs:
1. A marker tone is detected that is different from the one that was
present when MUTE was initiated or if the same tone returns after a
delay. (The delay accounts for a tone that fades and then comes
right back. The MUTE is reset if the aircraft is flown out of the cur-
rent tone and then back in.)
2. The audio panel is turned OFF.
3. If MUTE is pressed prior to crossing the marker beacon, the mute
will continue for 60 seconds and then timeout.