A nice little film of an early 90mm AA battery at practice. It gives a nice explanation of the director and rangefinder, and how that automatically controls the elevation and traverse of the guns.
Later, the optical rangefinder would be replaced by a radar rangefinder, usually an SCR-584.
Also, this was made before the proximity (or VT) fuze was in use. The time delay setting for each fuze was electrically sent from the director to each gun. On each mount, just to the left of the breech, there was a fuzesetter. Looking much like a cupholder, the ammo man would put the nose of each shell in the fuze setter, which would mechanically turn the fuze of the shell to the proper setting. The ammo man would hold the shell in until the casing of the previous round was ejected, and then pass the shell to the loader.
Obviously, once the VT fuze came into use, the fuze setter no longer had to be used.