Garmin GMA 347 User Manual
Page 13
Garmin GMA 347 Pilot’s Guide
190-00325-00 Rev. B
11
Operation
MARKER BEACON RECEIVER
The GMA 347 marker beacon receiver and
indicators are part of the ILS system. The marker
beacon lamps operate independently of any
audio selection and cannot be turned off. The
GMA 347 can drive external marker lamps if required and also
provides an autopilot middle marker sense output.
Prior to beginning an ILS approach, select high or low
marker sensitivity with the SENS key. The HI LED above the
SENS key illuminates for high sensitivity and remains off for
low sensitivity.
Pressing the MKR/MUTE key prior to an
approach allows the marker audio tones to be
heard in the headsets. When the MKR/MUTE
key illuminates, the marker audio will be heard.
Pressing the key again while audio is heard will mute the
marker audio until the next beacon is received.
Once the MKR/MUTE key is pressed, when a marker
beacon tone is received, pressing the MKR/MUTE key during
the tone SmartMutes the audio. That is, the audio turns off
and returns when the next marker signal is received.
The marker beacon signal sensitivity threshold can be set
in Configuration mode. Contact a Garmin-authorized service
center for adjustment.