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(2011) Service Advisory 1123 Rev A: GTN 635/GTN 650/GTN 750 Units and COM Transmit Audio Issue
AFFECTED PRODUCTS
GTN 635, 650, and 750 Units with Com software version 2.00.
DESCRIPTION
When interfaced with certain Apollo, PS Engineering, and Bendix/King Audio Panels, the GTN Com radio transmitted audio volume has been reported as low but still audible both to the pilot (sidetone audio) and to the listener (ATC, other aircraft, etc.) of the radio transmission. This low volume persists for about 3.5 seconds after the push-to-talk key is pressed; after that the volume increases to normal.
RESOLUTION
Garmin plans to correct this issue in a later software version.