A T-9 energy converter was a sensitive piece of equipment used on some remote Federation outposts.

In 2364, a Ferengi Marauder commanded by DaiMon Tarr stole a T-9 energy converter from an unmanned outpost on Gamma Tauri IV. The Starfleet vessel USS Enterprise-D was sent to pursue the Ferengi ship and retrieve the stolen equipment. (TNG: "The Last Outpost")