Garmin GMA 347 Pilot’s Guide
190-00325-00 Rev. A
5
Description
Microphones
The GMA 347 Audio Panel can accept up to six (6) micro-
phone inputs, allowing for a two-person crew and up to four
(4) passenger intercom stations in the aircraft.
NOTE: A push-to-talk (PTT) switch must be pressed
to transmit on a selected Transceiver.
Each microphone input has an automatic squelch thresh-
old. Manual squelch override and PTT keyed ICS operation
are also available. Each microphone has a dedicated VOX cir-
cuit to ensure that only the active microphone is heard when
squelch is broken.
Mono/Stereo Headsets
The unit can accommodate up to six (6) headsets (pilot,
copilot and up to four (4) passengers).
NOTE: The use of stereo headsets is highly recom-
mended. However, if monaural headsets are plugged
into stereo jacks the unit will not be damaged.
When wired correctly, the use of a monaural headset in a
stereo jack shorts the right headset channel to ground. Anyone
listening on a monaural headset hears only the left channel in
both ears. If a monaural headset is used at one of the passen-
ger positions, anyone else listening on a stereo headset hears
audio in the left ear only, unless their headset has a mono/ste-
reo switch set to mono.
NOTE: Incorrect aircraft wiring could short the left
channel or both channels to ground if a monaural
headset is plugged into the stereo jacks. If wired
incorrectly, failsafe operation will not work.
Intercom
The intercom system provides four modes of isolation:
Pilot, Copilot, Crew and All. In Pilot mode, the Pilot is isolated
from all other occupants of the aircraft. In Copilot mode, the
Copilot is isolated, while the Pilot and Passengers share the
intercom.
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