Unit XY-75847 reported detecting a Klingon fleet in their sector. This information was relayed to the USS Enterprise as she arrived at Organia in 2267. The unit's warning did not include the Klingon fleet's bearing in relation to the Enterprise.
The warning induced Captain Kirk to give Lieutenant Sulu specific orders regarding confrontation with the Klingon fleet: "do not fight – run, and return with the fleet." (TOS: "Errand of Mercy")
What Unit XY-75847 was never determined on screen.