The Garmin GTX 330ES is a panel-mounted Mode S digital transponder with Extended Squitter (ES) capability, enabling ADS-B Out on the 1090 MHz frequency.

It builds on the standard GTX 330 by adding automatic broadcast of aircraft position, velocity, and other data (without needing interrogation from ground stations or other aircraft), which improves surveillance and supports the FAA's ADS-B mandate (14 CFR 91.225/91.227) in the US.