GMA 340 Installation Manual
Page 2-7
190-00149-01
Rev. L
2.6.2
Failsafe Operation Check
1. Turn the unit off by rotating the pilot intercom knob (5) counter clockwise.
2. Check the failsafe operation by exercising the COM 1 microphone, microphone key and audio over the
headphones.
NOTE
For units without Mod 4 incorporated, if a monaural headset is plugged into a stereo
jack the ring conductor will be shorted to the barrel conductor when the headset is
plugged in preventing proper failsafe operation. No audio will be heard. In this type of
installation, either a stereo/mono switch must be installed for proper operation or Mod
4 must be incorporated. If Mod 4 is incorporated, the audio will be heard only in the
left channel of a stereo installation. See note 13 in figures B5 and B7 and refer to
Garmin Service Bulletin 0209.
3. Turn the unit back on to continue testing.
2.6.3
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.
2.6.4
Intercom System (ICS) Check
NOTE
If a monaural headset is used in one position, no damage will occur if plugging
into a stereo jack. In the case of passenger positions, any stereo listener will lose
one channel when another passenger plugs in a mono headset.
1. Set the intercom to the ALL mode [Crew (9) and Pilot (10) LEDs off.]
2. Plug in headsets at each ICS position.
NOTE
For helicopter operation using a two-stage Intercom/PTT switch, prior to using
the keyed-intercom mode, the VOX level should be set by adjusting the VOX
knob while the first detent is actuated and held.
3. Adjust squelch (8) and volume (7) for each position and verify that the ICS is working properly.
4. Check Pilot and Copilot ICS positions for isolation and proper operation of volume and squelch controls
(5, 6, 7 and 8).
5. Press the PA button (11). Verify that microphone audio is heard over the speaker.
