The Origins
The name of this Navy rating has changed back to Fire Controlman (FC). This was the original name of the job in the early days. After WWII, when the duties changed to more technical things like radar and computers, the name was changed to Fire Control Technician (FT). I was an FT the entire time I was in the Navy. The FT name is now used exclusively for Fire Control personnel on Submarines. The rating insignia, shown above, is an optical rangefinder (on a tripod), with two lightning bolts signifying the technical side. In my day, it was the rangefinder without the lightning bolts.
FCs maintain the control mechanism used in weapons systems on combat ships. Complex electronic, electrical, and hydraulic equipment is required to ensure the accuracy of guided missile and surface gunfire control systems. FCs are responsible for the operation, routine care, and repair of this equipment, which includes radars, computers, weapons-direction equipment, target-designation systems, gyroscopes, and rangefinders.
During my time in the Navy, I worked exclusively on gun fire control systems. I was never trained or assigned on missile control systems. I've worked on control systems for 40 MM, 3"/50 cal., 5"/38 cal., and 5"/54 cal. Naval guns. I attended the Navy's two long schools for FT. These were: (Basic) Class "A" and (Advanced) Class "B" schools. Each was nearly a year in length.