CERTIFICATION APPROVAL:
TSO Authorization

COMPLIANCE:
Optional

SYSTEM:
GTR225 / GTR225A / GTR225B / GNC255A / GNC255B

PURPOSE:
This Service Bulletin announces the availability of GTR 225/GNC 255 Display Software Version 2.11, USB Software Version 2.02, COM Software Version 2.20, and COM FPGA Version 2.4.

Display Software Version 2.11/USB Software Version 2.02 contain the following changes from Display Software Version 2.02/USB Software Version 2.01:

Added “Internal” COM sidetone configuration to improve the audio quality of the COM sidetone
Added configuration to allow the COM sidetone volume to change when the COM receiver volume is adjusted
Added automatic intercom squelch level adjustment setting (Intercom Auto VOX) to improve the performance of the intercom
Added setting to mute the auxiliary input during COM RX
Added setting to mute the intercom during COM RX
Added Advanced COM RX Squelch configuration to allow the COM radio sensitivity settings to be adjusted independently for low, mid, and high frequencies in both 8.33 kHz and 25 kHz channel spacing modes
Changed display of station identifiers for active and standby COM and NAV frequencies when connected to a GPS position source to match other Garmin products

Display Software Version 2.11 contains the following changes from Display Software Version 2.10:

The COM sidetone volume will be at the installer-configured level after power cycling the unit rather than being at a default level

COM Software Version 2.20/FPGA Version 2.4 contain the following changes from COM Software Version 2.13/FPGA Version 2.3:

Improved the performance of the intercom Manual VOX mode
Improved the intercom audio quality
Reduced noise burst (“Squelch Tail”) that occurs at the end of a reception
Reduced random squelch breaks (popping)