GARMIN GMA 340 User Manual

GMA 340

AUDIO PANEL

Pilot’s

Guide

®

MKR
BCN

ICS

Front Panel Controls

1. Marker Beacon Lamps

2. Marker Beacon Receiver Audio Select/Mute Button

3. Marker Beacon Receiver Sensitivity Indicator LED.

4. Marker Beacon Receiver Sensitivity Selection Button

5. Unit On/Off, Pilot Intercom System (ICS) Volume

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

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

Volume)

8. Copilot/Passenger VOX Intercom Squelch Level

9. Crew Isolation Intercom Mode Button

10. Pilot Isolation Intercom Mode Button

COM/
NAV

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11. Passenger Address (PA) Function Button

12. Speaker Function Button

13. Transceiver Audio Selector Buttons (COM1, COM2, COM3)

14. Transmitter (Audio/Mic) Selection Buttons

15. Split COM Button

16. Aircraft Radio Audio Selection Buttons (NAV1, NAV2, DME, ADF)

17. Annunciator Test Button

18. Locking Screw Access

19. Photocell - Automatic Annunciator Dimming

On, Off, and Fail-Safe Operation

The GMA 340 is powered off when the left small knob (5) is rotated fully CCW into the detent.
To turn the unit on, rotate the knob clockwise past the click. The knob then functions as the pilot
ICS volume control. A fail-safe circuit connects the pilot’s headset and microphone directly to
COM1 in case 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

NOTE

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

Selection of either COM1, COM2, or COM3 for both MIC and audio source is accomplished by
pressing either COM1 MIC, COM2 MIC, or COM3 MIC (14). The active COM audio is always
heard on the headphones.

Additionally, each audio source can be selected independently by pressing COM1, COM2, or
COM3 (13). When selected this way, they remain active as audio sources regardless of which trans­ceiver has been selected for microphone use.

When a microphone is keyed, the active transceiver’s MIC button LED blinks approximately
once per second to indicate that the radio is transmitting.

Split COM

Pressing the COM 1/2 button (15) activates the split COM function. When this mode is active,
COM1 is dedicated solely to the pilot for MIC/audio while COM2 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 COM3, NAV1, NAV2, DME, ADF, and MKR as selected. The split COM
mode is cancelled by pressing the COM 1/2 button a second time.

When in the split COM mode the copilot may make PA announcements while the pilot contin­ues using COM1 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.

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