guard against this possibility 'A' turret of Indefatigable was fitted with a 9-foot rangefinder at the rear of the turret roof and it was equipped to control the entire main armament during a refit between 1911 and 1914. Australia and New Zealand were built with a different arrangement. The spotting top on the main mast was deleted and an armoured spotting tower was built instead into the conning tower where it was better protected, had an improved field of vision and direct access to the primary conning position. The rear Transmitting Station was also deleted and the forward TS was consequently enlarged. Their 'A' turrets were built with the improvements listed above. Fire control technology advanced quickly during the years immediately preceding World War I and the development of the Dreyer Fire Control Table was one such advance. It combined the functions of the Dumaresq and the range clock and a simplified version, the Mk I, was fitted to the Indefatigables during refits in 1915–16. The more important development was the director firing system. This consisted of a fire-control director mounted high in the ship which electrically transmitted training and elevation angles to the gun turrets via pointers, which the turret crewmen had only to follow. The director layer's trigger fired the guns simultaneously which aided in spotting the shell splashes and minimized the effects of the roll on the dispersion of the shells. A gun within the 'Y' turret was also equipped with transmitters so that, as a backup, it could function as a "directing gun", but there was no provision for the gun battery to be split between the main director and this directing gun. The Indefatigables received their director equipment between mid-1915 and May 1916. Armour In some ways the armour protection given to the Indefatigables was weaker than that of their predecessors as the armour was reduced in thickness in a number of places, but it was spread out to a greater extent. The main belt ran from stem to stern; it was thick for the middle of the ship, but was reduced to abreast the end 12-inch gun barbettes and magazines and thinned still further to at the ends of the ship. A bulkhead met the barbette of X turret while the forward bulkhead was in thickness. The gun turrets and barbettes were protected by of armour, except for the turret roofs which used of