On. Off. and Failsafe Operation
The GMA 340 is powered off when the lelt smallknob (5, 7) is rotated frlly CCW into the detent.
To tum the unit on rotate the knob clockwrse past the click. The left small knobs also lunctions 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 I in case the power is intemrpted or the unit is tumed off.
Lighting
LED Button annunciator and markerbeacon lamp intensity are controlled automatica\by a bulhin
photocell on the front panel. Nomenclature backlighting is controlled by the aircraft dimmer buss.
Transceivers
Audio level is controlled by the selected C)M radio volume control.
SelectionofeitherCOM I,COM Z,orCON4 3(13)forbothMlCandaudiosourceisaccomplished
by pressrng either COM I N4lC, CON4 2 N4lC, or COM 3 MIC (14). The active com audio rs always heard
on theheadphones.
Additiona\ each audio source canbe selectedindependentlybypressrry COM 1, COM 2,or COM 3
(13) When selected in this way,they remain active as audio sources regardless olwhich transceiver has
been selected formicrophone use.
When a microphone is keyed, the active [ransceiver's MIC button LED blinks appro]omately once per
second to indicate that the radio is transmittlng.
Split COM (Not Available on Dual ADFI
Pressingthe CON{ l/2 button (15) actlates the Sp1lt COM function. When this mode is active,
COM I is dedicated sole1y to the pilot lor Ml0audio while COM 2 is dedicated to the copilot for MIO
audio. The pilot and copilot can srmuhaneously transmit in this mode over separate radios. Both pilots
can still listen to COM 3, NAV l, NAV 2, DI\4E, ADE and MKR as selected. The Split COM mode is
cancelled by pressrng the CON4 1/2 button a second time.
When rn the Split COM mode the copilot may make PA announcements whrle the pilot continues
usrry COM I independently When the PAbutton is pressed after the Split COM mode is activated, the
copilot's mic is output over the cabrn speaker when keyed. A second prcss of the PA button returns the
copilot to normal spht COM operation.
lf the C)M radios utilize a "transmit interlock" system, the Split C)M
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 C)M feature in a given
installation,
