Braun, Karl Ferdinand (1850-1918), German physicist, inventor, and Nobel Prize winner. Braun is best known for his invention of the first oscilloscope (an electronic instrument that displays changes in the voltage of an electric circuit) made out of a cathode-ray tube (CRT), but he also contributed much to the study of electricity and telegraphy, or wireless communication (see Radio), through groundbreaking research and inventions. He shared the 1909 Nobel Prize in physics with Italian electrical engineer and inventor Guglielmo Marconi for their work on wireless communication.

Born in Fulda, Braun studied at the University of Marburg and received his doctorate from the University of Berlin in 1872, after a dissertation on the vibrations of elastic rods and strings. He began his career as a research assistant at the University of Würzburg, and later held positions at universities in Leipzig, Marburg an der Lahn, Karlsruhe, and Tübingen, where he founded the Physics Institute. From 1880 to 1883 Braun was at Strasbourg, France, and he returned there in 1895 to become professor of physics and director of the Strasbourg Physics Institute.

In 1874 Braun published some of the results of his research on mineral-metal sulfides. He found that these crystals conducted electric currents in only one direction. At the time, the information was important in electrical studies and in measuring electrical conductivity, but Braun's discovery found practical application in the early 20th century when it was employed in crystal radio receivers. The crystal rectifier allowed current to flow in only one direction and improved radio transmission.

Braun also created the first oscilloscope, then called a Braun tube, in 1897. The Braun tube was a valuable laboratory instrument, and modified versions are used in electronic testing and research today. The principle of the Braun tube, moving an electron beam by means of alternating voltage, is the principle on which all television tubes operate.

While Braun also made many contributions to pure science, he won honors for his fundamental modification of Marconi's wireless transmitting system. Braun tried to overcome the difficulty in increasing the range of a transmitter beyond 15 km (9 mi). He believed he could expand this range by increasing the power of the transmitter.

Studying the Marconi transmitter, which used a sparking apparatus to produce periodic waves that travel through the air, he learned that attempts to increase the power output by increasing the length of the spark gap eventually reached a limit at which the spark caused a decrease in output. Braun solved this dilemma by producing a sparkless antenna circuit. He magnetically coupled the power from the transmitter to the antenna circuit using a transformer effect instead of having the antenna directly in the power circuit.

Braun's circuit has been applied to all similar transmission, including radio, radar, and television. A patent was granted on this circuit in 1899. Braun also invented a transmitter that channeled the transmission of electric waves in one direction.

Braun gained notoriety outside the laboratory as well when he was called to the United States in 1914 to testify in litigation involving radio broadcasting. He was still in the country in 1917 when the United States entered World War I, and he was not allowed to return to Germany. He died in a Brooklyn, New York, hospital in 1918.

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