 The shells and shot all had the same service weight of 94 pounds (to simplify calculation of elevation and depression) and diameter of ; therefore, lengths of the various types varied.In addition to these medium guns (intended to fend off an attack by up to six enemy light cruisers), smaller quick-firing guns were sited, in order to deal with the potential threat of fast, unarmoured torpedo boats.At Fort Rodd, a separate emplacement, called Belmont Battery was constructed to house two Quick-Firing 12-pdr guns, which were assisted by two sets of "Defence Electric Lights" (searchlights), which were powered by diesel engines and generators concealed in an engine room built into the landward side of a hill.