was fitted with another 9-foot rangefinder at the rear of the turret roof and a Mark I Dreyer Fire Control Table was installed in the main Transmitting Station. It combined the functions of the Dumaresq and the range clock. Fire-control technology advanced quickly during the years immediately preceding the First World War, and the most important development was the director firing system. This consisted of a fire-control director mounted high in the ship which electrically provided data to the turrets via pointers, which the turret crew were to follow. The director layer fired the guns simultaneously which aided in spotting the shell splashes and minimised the effects of the roll on the dispersion of the shells. A prototype was fitted in Dreadnought in 1909, but it was removed to avoid conflict with her duties as flagship of the Home Fleet. Preparations to install a production director were made during her May–June 1915 refit and every turret received a rangefinder at the same time. The exact date of the installation of the director is not known, other than it was not fitted before the end of 1915, and it was most likely mounted during her April–June 1916 refit. Armour Dreadnought used Krupp cemented armour throughout, unless otherwise mentioned. Her waterline belt measured thick, but tapered to at its lower edge. It extended from the rear of 'A' barbette to the centre of 'Y' barbette. Oddly, it was reduced to abreast 'A' barbette. A extension ran from 'A' barbette forward to the bow and a similar 4 inch extension ran aft to the stern. An bulkhead was angled obliquely inwards from the end of the main belt to the side of 'X' barbette to fully enclose the armoured citadel at middle deck level. An 8-inch belt sat above the main belt, but only ran as high as the main deck. One major problem with Dreadnoughts armour scheme was that the top of the 11 inch belt was only above the waterline at normal load and it was submerged by over 12 inches at deep load, which meant that the waterline was then protected only by the 8 inch upper belt. The turret faces and sides were protected by 11 inches of armour, while the turret roofs used 3 inches of Krupp non-cemented armour (KNC). The exposed faces of the barbettes were 11 inches thick, but the inner faces were 8 inches thick