GMA 340 Installation Manual
Page 3-5
190-00149-01
Rev. L
•
PILOT mode isolates the pilot from everyone else and dedicates the aircraft radios to the pilot
exclusively. The copilot and passengers share communication between themselves but cannot
communicate with the pilot or hear the aircraft radios.
•
CREW mode places the pilot and copilot on a common ICS communication channel. The passengers are
on their own intercom channel and can communicate with each other, but cannot communicate with the
crew or hear the aircraft radios.
•
ALL mode allows full intercom communication between everyone plugged in to the GMA 340. Aircraft
radios are heard by all.
•
MUSIC 1 and MUSIC 2 stereo entertainment inputs are affected by the intercom mode selected.
The following table summarizes the ICS operation for the different modes supported by the GMA 340.
MODE
PILOT HEARS
COPILOT HEARS
PASSENGER HEARS
MUSIC 1 MUTING
TRIGGERED BY
PILOT
(LED LIT)
Selected Radios.
Pilot.
Copilot.
Passengers.
MUSIC 1.
Passengers.
Copilot.
MUSIC 1.
Copilot or passenger
ICS activity.
CREW
(LED LIT)
Selected Radios. Pilot.
Copilot.
MUSIC 1.
Selected Radios.
Copilot. Pilot.
MUSIC 1.
Passengers.
MUSIC 2.
(MUSIC 1 in Dual
ADF)
Aircraft radio activity.
MKR activity.
Pilot or Copilot ICS
activity.
ALL
(LEDs
OFF)
Selected Radios.
Pilot.
Copilot.
Passengers.
MUSIC 1.
Selected Radios.
Pilot.
Copilot.
Passengers.
MUSIC 1.
Selected Radios.
Pilot.
Copilot.
Passengers.
MUSIC 1.
Aircraft radio activity.
MKR activity.
ICS activity.
MUSIC 1 is normally muted during ICS activity. However an installation option is available to disable ICS
MUTE. When ICS MUTE INHIBIT* (J2 pin 13) is connected to ICS MUTE INHIBIT RETURN (J2 pin 14),
muting of MUSIC 1 will not occur due to ICS activity. The MUSIC 1 mute trip level is adjustable through an
access hole in the top of the unit (see figure 2-3).
3.1.12 Mono/Stereo Headset
The use of stereo headsets is highly recommended. If monaural headsets are plugged into stereo jacks that do not
have a switch installed the unit will not be damaged.
Use of a monaural headset in a stereo jack shorts the right headset channel output to ground. A person listening
on a monaural headset will hear only the left channel from the GMA 340 in both ears. If a monaural headset is
used at one of the passenger positions, any other passenger listening on a stereo headset will hear audio in their
left ear only, unless their headset has a stereo/mono switch and it is set for mono.
In units without Mod 4 incorporated, if the pilot uses a monaural headset in a stereo jack, no audio will be heard
during failsafe operation. When using a monaural headset the pilot’s jack must be equipped with a stereo/mono
switch and it must be set to the ‘mono’ position for proper failsafe operation. If Mod 4 is incorporated, and the
pilot uses a stereo headset in a stereo jack, audio will be heard in the left channel only during failsafe operation.
