"Royal Air Force Radar, 1939-1945." Ground Control of Interception: AMES Type 15 mobile GCI station. The transmitter/receiver aerial can be seen on the left. The antenna was able to rotate around its vertical axis, and its output was displayed on a plan-position indicator (PPI) display. The Type 15 was used for traffic control in forward locations. The trailer on the right is a generator, providing power to the operations in the tent.