Data from a 9 feet coincidence rangefinder (an unstabilized Barr and Stroud instrument in HMS King George V 1911 2 and stabilized Argo units in the other ships) on the roof of the conning tower, together with the target's speed and course information, was input into a Dumaresq mechanical computer and electrically transmitted to a Dreyer Fire-control Table (a Mark III system in King George V and Mark II Tables in the others with an Argo range clock replacing the Dreyer-Elphinstone model in the Mark III) located in the transmitting station located on the main deck.