Garmin GMA 347 Installation Manual page 36

In the following procedural steps outlined below, allow for variations in
configuration settings for the particular unit under test.
3.8.1 Lamp Test
Apply power to the unit by rotating the Pilot's intercom volume knob clockwise out of the detent.
During power-up, the unit undergoes a self-test, illuminating all panel annunciator lights for
approximately two seconds (between 1/2 and 2 seconds).
Confirm the operation of the GMA 347 internal LED annunciators and marker beacon LED's. Cover the
photocell with a finger and observe that the LED annunciators dim automatically. Check the front panel
key backlighting and dimming function. Key brightness is controlled with the aircraft radio lights
dimming bus.
3.8.2 Failsafe Operation Check
1. Turn the unit off by rotating the Pilot's intercom volume knob counter clockwise.
2. Check the failsafe operation by exercising the COM 1 microphone, microphone key and audio
over the headphones. A stereo headset connected to the Pilot headphone jack will provide audio
in the left earphone only.
3. Turn the unit back on to continue testing.
3.8.3 Transceiver Operational Check
1. Perform a ramp test radio check by exercising the installed transceivers, microphone, microphone
key and audio over the headphones and speaker.
2. Verify that communications are loud and clear and PTT operation is correct.
Split COM performance varies significantly across installations and is
affected by both the distance between the antennas and the separation of
the tuned frequencies.
3. In appropriate installations, check for Pilot/Copilot microphone operation when using the Split
COM (COM 1/2 key) function.
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GMA 347 Installation Manual
190-00325-01