Garmin G3X Installation Manual page 709

Alert Source–If more than one GDU 45X/46X is installed, an Alert Source field will appear on the
SOUND Configuration page. The Alert Source item may be configured so a single specific GDU always
outputs alert audio. Or, the Alert Source item may be configured to "Auto", which will cause whichever
display is present to output alert audio, in the following priority order: PFD1, MFD1, PFD2, MFD2.
Alert Output–If set to Mono & Stereo, alert tones and messages will be output on both the mono and
stereo outputs. If set to Mono Only, alert tones and messages will be output only on the mono output.
190-01115-01 G3X/G3X Touch Install Manual - GDU 45X/46X Config and Post Install Checkout
Rev. AA Page 32-114