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Air-to-ground communication is the means by which people on the ground and those in airborne vehicles communicate with each other. Since the Wright brothers' first flight in 1903 in Kitty Hawk North Carolina, there has always been a question of how to communicate with pilots in the air. Originally it was seen as a very difficult task: ground controls used visual aides to provide signals to pilots in the air. Next came the advent of portable radios small enough to be placed in planes, which for the first time offered pilots the ability to communicate back to the ground. Today air-to-ground communication relies heavily on the use of many systems. Planes are outfitted with the newest radio and GPS systems as well as internet and video capabilities. ==Early systems== The early days of flight proved quite difficult for air-to-ground communication. Ground crews would rely on colored paddles, and hand signs and other visual aids. This was effective for ground crews, but it offered no way for pilots to communicate back. In the beginning of World War 1 planes were not outfitted with radios, so soldiers used large panel cut outs to distinguish friendly forces. These cut outs could also be used as a directional device to help pilots navigate back to friendly airfields. As technology developed planes were able to use telegraph systems to send messages in Morse code. Telegraphs used a plunger to complete an electric circuit. When the circuit was completed it sent out a signal as a dot or a dash. By depressing the plunger devise in a rhythmic pattern a telegraph operator could spell out words, with each dot- dash sequence representing a corresponding letter in a word. Using this technology planes were able to call in accurate artillery fire and act as forward observers. In 1912 the Royal Flying Corps had begun experimenting with "wireless telegraphy" in aircraft. Lieutenant B.T James was a leading pioneer of wireless (radio) in aircraft. In the spring 1913, he had begun to experiment with radios in a B.E.2a. James brought the science of wireless in aircraft to a high state of efficiency before he was shot down and killed by anti-aircraft fire on 13 July 1915. In April 1915 Captain J.M. Furnival was the first person to hear a voice from the ground when Major Prince said “If you can hear me now it will be the first time speech has ever been communicated to an aeroplane in flight.” In June 1915 the world's first air-to-ground voice transmission took place at Brooklands (England) over about 20miles (ground-to-air was initially by morse but it is believed 2-way voice communications was being achieved by July 1915). In early 1916 the Marconi Company (England) started production of air-to-ground radio transmitters/receivers which were used in the war over France. In 1917 AT&T invented the first American air-to-ground radio transmitter. They tested this device at Langley Field in Virginia and found it was a viable technology.〔(【引用サイトリンク】title=Technology Timeline - The First Air-to-ground & Ground-to-air Communication )〕 In May 1917, General George Squier of the U.S. Army Signal Corps contacted AT&T to develop an air-to-ground radio with a range of 2,000 yards. By July 4th of that same year AT&T technicians achieved two-way communication between pilots and ground personnel.〔 This allowed ground personnel to communicate directly with pilots using their voice instead of morse code. Though few of these devices saw service in the war, they proved this was a viable and valuable technology worthy of refinement and advancement. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Air-to-ground communication」の詳細全文を読む スポンサード リンク
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