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was confident that producing a system capable of higher definition images "was only a matter of money". However, at the cost of ÂŁ15 (US$ 45) per selenium cell, he estimated that a 4,000 cell system would cost ÂŁ60,000 (US$ 180,000), and a 10,000 cell mechanism capable of reproducing "a scene or event requiring the background of a landscape" would cost ÂŁ150,000 (US$ 450,000). Because of the high cost, he didn't foresee his device as suitable for private home use, instead envisioning that central offices in major cities could be established, and customers would make arrangements to make use of the service.
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this photographic strip, by shining a bright light through the running filmstrip, with the resulting varying light illuminating a selenium cell. The changes in brightness caused a corresponding change in the selenium's resistance to electrical currents, which was used to modulate the sound produced in a telephone receiver. He summarized the results as: "It is truly a wonderful process: sound becomes electricity, becomes light, causes chemical actions, becomes light and electricity again, and finally sound." He called this invention the
69:. Bell introduced this device in 1880, which used selenium cells in the receiver to convert the fluctuating light produced by the transmitting unit into sounds. But Bell's invention only had a range of a few hundred meters, and he soon ended his research into this device. Ruhmer believed that the increased sensitivity of his selenium cells, combined with the superior receiving capabilities of professor H. T. Simon's "speaking arc", would make the photophone practical over longer signalling distances.
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140:. This book reviewed the various technologies being investigated for wireless telephony, including both optical telephone research and the newer radiotelephone developments. Radio transmissions were soon recognized to be superior for most applications, as they were unaffected by weather, and were not limited to line-of-sight transmissions.
117:, he reported that he had constructed a transmitter capable of producing frequencies up to 300,000 cycles-per-second. Although the quality of the resulting audio transmissions were "strikingly good", and he felt that transmission range could be extended to several kilometers, these tests were only conducted over a distance of 500 meters.
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In 1900, as part of his optical wireless telephone research, Ruhmer recorded the fluctuations of the transmitting arc-light as varying shades of light and dark bands onto a continuous roll of photographic film. He then determined that he could reverse the process and reproduce the recorded sound from
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Ruhmer also investigated radiotelephone transmissions using a high-frequency spark transmitter. This work took place during winter 1904-5, however, this approach had limited results, as he later noted that "the transmitted speech received on microphonic contact and telephone was rough and broken like
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Ruhmer's father was an inventor and manufacturer. From 1897 to 1900 he studied mathematics and natural sciences in Berlin, and the next year continued his studies in
Giessen. His early work included extensive research in developing selenium cells that were more sensitive, and faster reacting, to the
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at
Brussels to the city of Liege, a distance of 115 kilometers (72 miles). This demonstration was described at the time as "the world's first working model of television apparatus". However, his device consisted of only 25 cells, thus was only capable of representing simple geometric shapes. Ruhmer
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Ruhmer also carried out research in making audio transmissions using radio signals. In 1904, he was granted, along with Adolf Pieper, German patent 173,396, "A Process for
Generating Permanently Undamped Electrical Oscillations", which described a method for creating "continuous wave" transmissions
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were issued German patent 151,971 for their method of producing photographic images by exposing electrically conductive selenium-coated plates. Ruhmer also designed a light-sensitive control switch, using a selenium cell, which was successfully used to automatically turn off the flow of a buoy's
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transmissions (then commonly known as "wired wireless"), where multiple radio signals are transmitted along an electrical conductor, which acts as a wave guide carrying the signals to designated locations. In 1911, it was reported that during a recent demonstration, "four transmissions—German,
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and on Lake
Wannsee from 1901 to 1902. He reported achieving sending distances under good conditions of 15 kilometers (9 miles), with equal success during the day and at night, although the longest transmissions were dependent on having clear weather. He continued his experiments around Berlin
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would sponsor the construction of an advanced device with significantly more cells, as a showcase for the exposition. However, the estimated expense of ÂŁ250,000 (US$ 750,000) proved to be too high. Also, television research turned to using
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Ruhmer also researched using selenium cells as the picture elements for a television receiver. In late 1909 he successfully demonstrated in
Belgium the transmission of simple images over a telephone wire from the
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In 1904 he developed a high-speed alternator which produced transmitting frequencies of up to 120,000 cycles-per-second. However, this effort never got beyond a basic prototype that generated less than .001 watt.
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Ruhmer demonstrating his experimental television system, which was capable of transmitting images of simple shapes over telephone lines, using a 25-element selenium cell receiver (1909)
26:, which he employed in developing wireless telephony using line-of-sight optical transmissions, sound-on-film audio recording, and television transmissions over wires.
22:(15 April 1878 – 8 April 1913) was a German physicist. He was best known for investigating practical applications making use of the light-sensitivity properties of
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French, song and gramophone music respectively—were effected simultaneously, but the number can obviously be increased considerably without any disturbance".
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through 1904, in conjunction with the German Navy, which supplied high-powered searchlights for use in the transmissions.
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illuminating gas during daylight hours. In 1904 he established a private physics laboratory, located in southwest Berlin.
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Ruhmer's promising career was eventually cut short. He fell ill in 1912, and died the next year at the age of 34.
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by Ernst Ruhmer (translated from the German by James
Erskine-Murray), 1908.
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Ruhmer first gained widespread recognition for his work on improvements to
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Ruhmer carried out a series of experimental transmissions along the
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246:"Fernsehleute im Spannungsdeld zwischen Fortschritt und Reaktion"
153:. The general concept would eventually be adopted for producing
468:"Pioneer Experiments of Eugene Lauste in Recording Sound"
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effects of light illumination. In
December 1902 he and
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by
William J. Hammer, April 17, 1903 lecture, page 57.
454:, January 31, 1910, pages viii-x (reprinted from the
472:Journal of the Society of Motion Picture Engineers
182:Ruhmer expressed the hope that the 1910 Brussels
109:In 1906, employing a design largely based on the
307:Wireless From Marconi's Black-Box to the Audion
279:(October 30, 1902 letter from Ernst Ruhmer),
228:"The Properties and Applications of Selenium"
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248:by Manfred Hempel (in German), included in
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388:Wireless Telephony In Theory and Practice
294:Wireless Telephony In Theory and Practice
138:Wireless Telephony In Theory and Practice
185:Exposition Universelle et Internationale
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233:Radium and Other Radioactive Substances
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218:(in German), June 15, 1904, page 578.
193:in receivers as a superior approach.
97:Ruhmer's radiotelephone transmitter,
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277:"Correspondence: Wireless Telephony"
250:Die Anfänge des Deutschen Fernsehens
297:by Ernst Ruhmer, 1908, pages 49-59.
86:using a mercury-vapor vacuum-tube.
65:'s optical wireless telephone, the
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429:"Another Electric Distance-Seer"
309:by Hong Sungook, 2001, page 166.
435:, September 11, 1909, page 385.
371:"Ruhmer's Multiplex Telephony"
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517:20th-century German inventors
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330:Goldsmith, Alfred N. (1918)
16:German physicist (1878–1913)
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136:and published in 1908 as
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111:hydrogen arc transmitter
144:Sound-on-film recording
113:developed by Denmark's
413:"The Photographophone"
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106:that of a stammerer".
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128:In 1907 Ruhmer wrote
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63:Alexander Graham Bell
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487:"Wireless Telephony"
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130:Drahtlose Telephonie
522:Television pioneers
417:Scientific American
20:Ernst Walter Ruhmer
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415:by Ernst Ruhmer,
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161:Television
67:photophone
49:Photophone
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24:selenium
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30:Career
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