Type E/F-band (3 GHz spot frequency) 3-D early warning, Ground-Controlled Interception (GCI) and Air Traffic Control (ATC) radar. Description The ground-mobile 1L117 3D early warning, GCI and ATC radar is an upgraded version of the P-37 early warning and GCI system that is 'almost entirely' solid-state (with the exception of its coaxial magnetrons and cathode ray tubes).