A director is the equipment occupying a centralised firing position on a naval ship. It tells the guns where to point and when to fire, and thus harmonises their destruction in coherent salvoes.
In its fullest implementation, the director firing principle most often attributed to Percy Scott relies upon a director and its crew to indicate the proper elevation and training angle for the barrels and turrets of a group of guns, as well as providing the firing impulse for a simultaneous salvo.
A director is very similar to a small gun mounting except that it lacks a gun. A typical gunnery director has a calibrated sight that can be set to a desired range and deflection, and hand wheels and telescopes by which crew can elevate and train it such that the crosshairs are on the object to be fired upon. The elevation angle and training angle resulting from these motions is continually signaled by electro-mechanical data circuits to the guns so the gun crews can mimic the proper motions. When the crosshairs are correctly positioned, a press on a pistol-type trigger sends an electrical impulse to cause the guns to fire.
Directors varied in their particulars according to nation and type. Amongst the most complete of the World War I era was the Royal Navy's Vickers light aloft director, which housed 4 crew: a director layer, a director trainer, a sightsetter, and a talker.
The talker was equipped with a telephone headset and often a flexible speaking tube snaking in from the spotting top above. He would act as the communication interface for any miscellaneous commands and criticisms that were not fully conveyable by the data receivers and gongs nearby.
The sightsetter had an F.T.P. sight to adjust to the range and deflection being continually indicated upon it from the transmitting station. As on any pedestal-mounted gun with a settable sight, this action rotated a pair of telescopes in a backwards manner so the elevation and deflection angles would be applied in the opposite direction.
The director trainer would use his handwheels to rotate the entire director assembly (a small bathtub-like cupola on the lip of which all 4 crew sat as if attending a tea party) and the top of the external housing until he saw the target aligned in his telescope.
The director layer would use his handwheel to elevate his crosshairs (whose elevation had been altered as the sightsetter dialed in the desired gun range). When the target was aligned and a small gun ready display board showed a sufficient number of guns were ready to fire, the director layer would pull a trigger with his free hand to signal the firing impulse.
Variant Director Designs
In addition to the light aloft mounting, Vickers tripod directors were also employed in armoured director mountings in several capital ships. A significant adaptation required in such cases was that the mechanical training handles and gearing was not powerful enough to rotate the massive armoured hood the director sat inside. To work around this, the director was made mechanically separate from the hood, and a separate man was tasked with hydraulically training the hood so that its telescope apertures remained in front of the director's telescopes. This added man was situated in a compartment below the director, and read its present training angle (relative to the keel) via a mechanical receiver, allowing him to match it with the hood's hydraulic travel.
The Vickers director design was scaled down late in the war (1917 onward?) into a pedestal-mounted form suitable for use in destroyers and to direct the secondary batteries of dreadnoughts. This was similar in conception to the fully equipped director, but the crew stood and shuffled around the pedestal as it was trained, just as a pedestal gun crew would be required to do. Additionally, any talker helping out the crew was seen as incidental, as there was no integral support in the equipment for his presence.
The Royal Navy also applied the director principle to the use of a directing gun, wherein one gun and its mounting would transmit elevation and training angle to the others. The gun would then be laid and fired locally, discharging all guns connected to it via the director circuits. This mode of director fire was generally intended as a last resort if all other directors were knocked out or were already directing a subgrouping of the battery's weapons.
The German director system did not include elevation — just training. Consequently, neither did it include a firing trigger impulse; the individual gun layers would independently fire their own guns upon hearing a gong which rang when the gunnery officer pressed a firing button). The result of this was that German ships fired their salvoes in a semi-simultaneous fashion, and not as cleanly as a British ship did with its central electrical firing circuitry. Presumably, German salvoes also manifested a greater range spread than the British salvoes would achieve if all other factors were equal, as the German guns were all independently pointed in elevation.