A Popham panel, or T-signalling panel, was a means of ground-to-air communication, in Morse code, developed during the First World War, before the introduction of radio communication. They were named for Robert Brooke-Popham and were used by the British and American armed forces.
They were used in the Waziristan campaign of 1919–1920, and in the Kabul Airlift of 1928, and remained in use as a reserve method of communicating with aircraft as late as just before the Second World War. They were eventually rendered obsolete by the development of effective radio communication with aircraft.