Gravitronics was section aboard Regula I during the late 23rd century. It was located across from geoplastics.
Doctors Carol and David Marcus passed a door labelled "gravitronics" as they walked through the corridor from the lab in thermonics discussing Admiral James T. Kirk.
Kirk, Leonard McCoy, and Saavik later beamed in from the USS Enterprise to the same location. (Star Trek II: The Wrath of Khan)