Dear Colleagues, I decided to join this forum because of the very interesting subjects, detailed information and quality of discussion. Can the experts explain how the Cold War EE Lightning's GCI data link worked and whether it was based on an AM radio channel data transmission via the on-board PTR-175 VHF/UHF transceiver, which had to be preset to the DL or DL/T mode? What kind of data was transmitted from the aircraft in the DL/T mode? How GCI commands were shown to the pilot in the Lightning's office? I assume a dedicated system to decode and process the signals aired from a GCI station was needed (like the ARI 18168/2). Was this GCI data link also available on export Lightnings? What was the nomenclature on the GCI ground processor and transmitter that interoperated with the EE Lightnings? Looking forward to your inputs. Best wishes.