Release notes for v3.4 firmware update:
Changes made from version 3.00 to 3.40:
PLEASE NOTE: You must update your Edge device and Radar Display Unit to maintain compatibility with the Radar Tail Light.
IMPORTANT: Before updating, read the update instructions in the online owner's manual. To access the manual go to the main device dashboard in Garmin Express, go to Tools -> Help and Manuals. In the manual, the instructions are under Troubleshooting -> Support and Updates.
CHANGES: Improved vehicle tracking
ANT+ communication improvements
From: http://www8.garmin.com/support/download_details.jsp?id=9281