Christian Hulsmeyer

Christian Hulsmeyer was a German inventor and physicist who, building on Heinrich Hertz's discovery that electromagnetic waves reflect off metal, developed the telemobiloscope, a transmitter-receiver system meant to warn ships of unseen obstacles. He applied for a German patent on the device in 1904 and demonstrated it publicly that year in Cologne and in Rotterdam harbor, where it detected vessels at ranges of roughly five kilometers. The shipping lines that watched the demonstrations were impressed, but every one of them declined to adopt the device commercially, reasoning that a ship's own steam whistle already carried farther than the telemobiloscope's range, and Hulsmeyer abandoned further development by 1905. He went on to file more than 180 further patents and became a wealthy man, but the telemobiloscope itself was largely forgotten until historians of radar identified it decades later as the first working device of its kind, patented three decades before Robert Watson-Watt's Daventry Experiment produced an operational radar network.