Starbase Sierra Tango was a Federation starbase that was administered by Starfleet.
In the 2370s, this starbase was the point of origin for tactical computer modules, which were delivered to Deep Space 9. This outpost was mentioned on a "DS 9 Routines and Duty Roster". (DS9: "The Assignment")
The wardroom graphic, which was seen in the far background in the episode, can be clearly read at Yourprops.com. [1]