Garmin GMA 340 User Manual

GMA 340

Audio Panel

pilot’s guide

1

Front Panel Controls (GMA 340)

Front Panel Controls (GMA 340 Dual ADF)

Front Panel Controls (GMA 340H)

2

Function Selection Switches

The left small knob (5, 7) on all units controls ON/OFF function.

1. Marker Beacon Lamps

MKR
BCN

ICS

COM/
NAV

2. Marker Beacon Receiver Audio Select/Mute Button

3. Marker Beacon Receiver Sensitivity Indicator LED’s

4. Marker Beacon Receiver Sensitivity Selection Button

5. Pilot Intercom System (ICS) Volume (Also Passenger Volume on 340H)

6. Pilot ICS Voice Activated (VOX) Intercom Squelch Level

7. Copilot and Passenger ICS Volume Control (Pull out for Passenger Volume)

8. Copilot and Passenger VOX Intercom Squelch Level

9. Crew Isolation Intercom Mode Button

10. Pilot Isolation Intercom Mode Button

11. Passenger Address (PA) Function Button

12. Speaker Function Button

13. Transceiver Audio Selector Buttons (COM 1, COM 2, COM 3)

14. Transmitter (Audio/Mic) Selection Buttons

15. Split COM Button (Not Available in Dual ADF)

16. Aircraft Radio Audio Selection Buttons (NAV 1, NAV 2, DME, ADF 1, ADF 2)

17. Annunciator Test Button

18. Locking Screw Access

19. Photocell – Automatic Annunciator Dimming

3

On, Off, and Failsafe Operation

The GMA 340 is powered off when the left small knob (5, 7) is rotated fully CCW into the detent.
To turn the unit on rotate the knob clockwise past the click. The left small knobs also functions as the
pilot or copilot’s ICS volume control on the appropriate unit. A failsafe circuit connects the pilot’s headset
and microphone directly to COM 1 in case the power is interrupted or the unit is turned off.

Lighting

LED Button annunciator and marker beacon lamp intensity are controlled automatically by a built-in
photocell on the front panel. Nomenclature backlighting is controlled by the aircraft dimmer buss.

Transceivers

F

by pressing either COM 1 MIC, COM 2 MIC, or COM 3 MIC (14). The active com audio is always heard
on the headphones.

(13). When selected in this way, they remain active as audio sources regardless of which transceiver has
been selected for microphone use.

second to indicate that the radio is transmitting.

Split COM (Not Available on Dual ADF)

COM 1 is dedicated solely to the pilot for MIC/audio while COM 2 is dedicated to the copilot for MIC/
audio. The pilot and copilot can simultaneously transmit in this mode over separate radios. Both pilots
can still listen to COM 3, NAV 1, NAV 2, DME, ADF, and MKR as selected. The Split COM mode is
cancelled by pressing the COM 1/2 button a second time.

using COM 1 independently. When the PA button is pressed after the Split COM mode is activated, the
copilot’s mic is output over the cabin speaker when keyed. A second press of the PA button returns the
copilot to normal Split COM operation.

F

Audio level is controlled by the selected COM radio volume control.

Selection of either COM 1, COM 2, or COM 3 (13) for both MIC and audio source is accomplished

Additionally, each audio source can be selected independently by pressing COM 1, COM 2, or COM 3

When a microphone is keyed, the active transceiver’s MIC button LED blinks approximately once per

Pressing the COM 1/2 button (15) activates the Split COM function. When this mode is active,

When in the Split COM mode the copilot may make PA announcements while the pilot continues

If the COM radios utilize a “transmit interlock” system, the Split COM
function may require that this feature is enabled. Refer to the radio’s
installation manual for guidance. GARMIN makes no expressed or implied
guarantees regarding the suitability of the Split COM feature in a given
installation.

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