A major advance in the D Class was the incorporation of a wireless system for the first time, the aerial being rigged to the submarine's mast. Before diving, the mast had to be lowered by hand and the wireless aerial stowed away along the side of the vessel. Previous submarines had been equipped with receiving sets, but the D Class was the first to have both receiving and transmitting facilities; unfortunately, wireless signals could neither be received nor transmitted when submerged - that problem remaining unsolved until the late 1920s.
