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Topic: Photophone

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	Photophone - Wikipedia, the free encyclopedia
		The idea of the photophone was thus to modulate a light beam: the resulting varying illumination of the receiver would induce corresponding varying resistance in the selenium cells, which could be used by a telephone to regenerate the sounds captured at the receiver.
		The photophone functioned similarly to the telephone, except the photophone used light as a means of projecting the information, while the telephone relied on electricity.
		Bell's photophone is recognized as the progenitor of the modern fiber optics that today transport over eight percent of the world's telecommunications.
	en.wikipedia.org /wiki/Photophone (446 words)

	NationMaster.com - Encyclopedia: Photophone
		The photophone used crystalline (A toxic nonmetallic element related to sulfur and tellurium; occurs in several allotropic forms; a stable gray metallike allotrope conducts electricity better in the light than in the dark and is used in photocells; occurs in sulfide ores (as pyrite)) selenium cells as the receiver.
		The photophone functioned similarly to the telephone, except the photophone used light as a means of projecting the information, while the telephone relied on (A physical phenomenon associated with stationary or moving electrons and protons) electricity.
		Bell's photophone is recognized as the progenitor of the modern fiber optics that today transport over eight percent of the world's ((often plural) systems used in transmitting messages over a distance electronically) telecommunications.
	www.nationmaster.com /encyclopedia/Photophone (1285 words)

	Alexander Graham Bell - Wikipedia, the free encyclopedia
		Another of Bell's inventions was the photophone, a device enabling the transmission of sound over a beam of light, which he developed together with Charles Sumner Tainter.
		The device employed light-sensitive cells of crystalline selenium, which has the property that its electrical resistance varies inversely with the illumination (i.e., the resistance is higher when the material is in the dark, and lower when it is lighted).
		The photophone was patented on December 18, 1880, but the quality of communication remained poor and the research was not pursued by Bell.
	en.wikipedia.org /wiki/Alexander_Graham_Bell (2424 words)

	The Photophone
		The ensuing vibrations would distort the mirror and create variations in the beam of light striking the selenium cell, which in turn led to the varying of the electrical current flowing through the circuit.
		By 1880, Bell could observe audible effects over a distance of 270 feet (82 metres), and was optimistic that the photophone would replace electrical transmitters that depended on the use of wires.
		The two parts of the photophone had to be in sight of each other to be able to function.
	www.abheritage.ca /telephone/era/photophone.html (302 words)

	Alexander Graham Bell - Simple English Wikipedia
		These included fourteen for the telephone and telegraph, four for the photophone, one for the phonograph, five for aerial vehicles, four for hydroairplanes, and two for a selenium cell.
		In 1888, he was one of the original members of the National Geographic Society and became its second president.
		The photophone was patented on December 18, 1880.
	simple.wikipedia.org /wiki/Alexander_Graham_Bell (1405 words)

	Photophone: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-10-21)
		Bell believed the photophone was his most important invention invention quick summary:
		The idea of the photophone was thus to modulate a light beam: the resulting varying illumination of the receiver would induce corresponding varying resistance in the selenium cells, EHandler: no quick summary.
		Bell's photophone is recognized as the progenitor of the modern fiber optics that today transport over eight percent of the world's telecommunication telecommunication quick summary:
	www.absoluteastronomy.com /encyclopedia/p/ph/photophone.htm (1018 words)

	RCA Photophone - Wikipedia, the free encyclopedia
		The Photophone system was initally inferior to the Western Electric system, but with the work of the RCA engineers it eventually superceeded that system.
		The Photophone was a variable area film exposure system.
		The modulated area corresponded to the amplitude of the audio signal.
	en.wikipedia.org /wiki/RCA_Photophone (194 words)

	Alexander Graham Bell Invented the Photophone
		Bell's photophone was based on transmitting sound on a beam of light.
		The vibrations of the voice caused similar vibrations in the mirror.
		Sunlight was then directed into the mirror, where the vibrations were captured and projected back to the photophone's receiver.
	www.americaslibrary.gov /cgi-bin/page.cgi/jb/gilded/bell_3 (109 words)

	Canonla (Site not responding. Last check: 2007-10-21)
		Photophone for communication with fort No. 3, with a narrow safety exit below it.
		Another photophone oriented Westwards, but I was unable to locate any fort there.
		Furthermore, since fort No. 1 is situated above it (not to the West), it is unclear whether the photophone was used for communication with some other position (or, for instance, barracks...).
	free-ri.htnet.hr /fortress-fiume/Canonla.htm (400 words)

	Chapter 5.4: Turning Students into Inventors
		This group elected to work with Bell's photophone, on the grounds that it had the most room for improvement, resembled modern ideas like fiber optics and might be easier to manage than messy liquids and ground carbon.
		Their initial information about the photophone came from a brochure describing a December 1976, exhibit at the National Museum of American History entitled "Person to Person"; page 6 showed how one could build a simple photophone using a flashlight, a tin can, a solar cell and a couple of batteries (see http:repo-nt.tcc.virginia.edu/classes/tcc315/alm/telephone/exhibits/build.html).
		The students in the photophone group had to make the same kind of change in direction after they submitted their caveat, revising their original intentions in the light of their interference with Bell's actual photophone patent.
	repo-nt.tcc.virginia.edu /book2/chapter5sec4.htm (7144 words)

	RCA Types PB-31, PB-140, PB-144, 44-A, 44-B
		The succession of RCA ribbon and magnet velocity microphones was rooted in the elegant, machine-age design of the Photophone PB-31.
		For those unfamiliar with the sound characteristic of the Photophone PB-31, it could be best described as flat and dark, very similar to the sonics and gain level of the 44-A. This mic has excellent high frequencies, and most people are startled to hear a seventy-year old microphone sound so modern.
		RCA and Western Electric were in fierce competition for theater sound business, and whenever a system was installed or, more importantly, when the competitor’s system was replaced, one of these plaques was installed in the lobby or on an outside wall where they could not be missed by the patrons.
	www.coutant.org /pb31 (2830 words)

	Document Image Transmission by Telecommunication
		Photophone® is an image-transmission device which uses telecommunications to transmit questioned documents for examination on an international scale.
		The Photophone video camera and zoom lens can be focused close up on a document, or on a particular portion of a document, or even out to infinity to capture a high-fidelity image on the Photophone screen.
		Photophone creates for the INS a vitally integrated system for examination of questioned documents and identifying individuals at all U.S. Ports of Entry and offices containing a Photophone.
	www.astm.org /JOURNALS/FORENSIC/PAGES/1876.htm (208 words)

	Investigating 'Photophone'.
		This is a totally multi-media presentation, which gives you the power to choose from straightforward descriptions, more in-depth study, images of exhibits in 3D, reminiscences in oral and written form from people who worked in the telecommunications industry in former times, movie sequences, and simple explanations or interactive animations of the way that technology operates.
		Connected Earth is an appropriate place to continue your study of the subject photophone.
		In addition to looking for information that specifically answers your questions, you'll be able to choose from 9 different galleries.
	www.connected-earth.com /content/photophone_online.html (281 words)

	Adventures in CyberSound: Bell, Alexander Graham (Site not responding. Last check: 2007-10-21)
		In 1880 he invented the photophone and the graphophone and went on to found the journal 'Science' in 1883.
		He invented the photophone, transmission of sound on a beam of light, and the graphophone, a practical approach to sound recording.
		These included 14 for the telephone and telegraph, 4 for the photophone, 1 for the phonograph, 5 for aerial vehicles, 4 for hydroairplanes, and 2 for a selenium cell.
	www.acmi.net.au /AIC/BELL_BIO.html (2398 words)

	Smithsonian Press--Legacies--3Palace of Progress--Photophone invented by Alexander Graham Bell and Sumner Tainter, 1880 (Site not responding. Last check: 2007-10-21)
		In 1880 Bell established the Volta Laboratory in Washington, D.C., to undertake inventions beyond the telephone.
		That year he and his associate Sumner Tainter deposited at the Smithsonian two sealed tin boxes containing models and documentation of a device they called a photophone, which transmitted sound over a beam of light, and other apparatus.
		The inventors hoped that the sealed boxes would prove their priority in invention; they did not want to file a patent for fear of giving away secrets that would help competitors.
	www.smithsonianlegacies.si.edu /objectdescription.cfm?ID=134 (138 words)

	Photoacoustic and Photothermal Phenomena (Site not responding. Last check: 2007-10-21)
		Bell's photophone consisted of a voice-activated mirror, a selenium cell, and an electrical telephone receiver.
		Since the electrical resistance of selenium depend on the intensity of light falling on it, the voice-modulated beam of sunlight occured in electrically reproduced telephonic speech.While experimenting with the photophone, Bell observed that it was possibile to obtain, at times, an audible signal directly, that is in a nonelectrical fashion.
		This phenomenon occured if the beam of light was rapidly interrupted with a rotating slotted disk, and than focused on selenium, or onto solids that were in the form of diaphragms connected to a hearing tube.
	www.movar.pate.hu /~mathphys/pas.html (791 words)

	A Brief History of Fiber Optic Technology
		The photophone used free-space light to carry the human voice 200 meters.
		This resistor was connected to a battery that was, in turn, wired to a telephone receiver.
		As one spoke into the photophone, the illuminated diaphragm vibrated, casting various intensities of light onto the selenium resistor.
	www.fiber-optics.info /fiber-history.htm (2006 words)

	RCA Photophone Wall Plaque (Site not responding. Last check: 2007-10-21)
		Western Electric was the pioneer in this field, both with the Vitaphone system, and their slightly later sound-on-film system.
		RCA entered the field in 1928 with their own sound-on-film system which they called "Photophone".
		These two companies were in fierce competition for the theatre sound business throughout the 1930's.
	uv201.com /Misc_Pages/rca_photophone.htm (165 words)

	First Radio Built by San Diego Resident (Site not responding. Last check: 2007-10-21)
		That was even eight years before Heinrich Hertz, the German physicist and electrician, laid the foundation and understanding for electrical wave communication by describing and demonstrating the "Hertzian waves." Their "photophone" and their method were somewhat different than the instrument and the system later employed in wireless and radio.
		Besides being associate inventor of the "photophone," or "radiophone," he is credited wth invention ofthe dictaphone, of that rival to Edison's phonograph, the graphophone, and of the first engraved and first disk talking-machine records.
		The San Diegan was awarded a gold medal at the Paris Electrical exhibition of 1881 for his part in the invention of the "photophone." In 1889, he was made "Officer de l'Instruction Publique" of France for his graphophone inventions.
	history.acusd.edu /gen/recording/ar304.html (1279 words)

	jimi tenor : tenorvision : gear
		The Photophone is a light sensitive synth constructed from a rotating fan, a photocell and a piece of specially exposed fl and white film.
		A special cylindrical version of the photophone was introduced at the Barbican show in September 2000.
		Sirkka, a man-sized mechanical drum machine, is a sturdy device consisting of a couple of oil barrels which are hit by two large hammers.
	www.jimitenor.com /gear.html (386 words)

	Interesting Engineering event (Site not responding. Last check: 2007-10-21)
		Optical Fiber is also more lightweight compared to copper cabling because it is a thin glass strand and has huge bandwidth because information travels along the fiber at the speed of light.
		In the decades that followed, light was used for a few special applications, such as signalling b etween ships, but otherwise optical communications, like the experimental Photophone Bell donated to the Smithsonian Institution, languished on the shelf.
		Although the photophone was an extremely important invention, it was many years before the significance of Bell's work was fully recognized.
	www.pitt.edu /~irr1/engrevent.html (2049 words)

	Alexander Graham Bell
		His output included the bel and decibel, photophone, metal detector, experimental aircraft, hydrofoil, and eugenics.
		Among one of Alexander's first innovations after the telephone was the "photophone," a device that enabled sound to be transmitted on a beam of light — the principle upon which today's laser and fiber optic communication systems are based.
		Bell and his assistant, Charles Sumner Tainter, developed the photophone using a sensitive selenium crystal and a mirror that would vibrate in response to a sound.
	www.u-s-history.com /pages/h1797.html (864 words)

	Using Sunlight to Intercept Audio (Site not responding. Last check: 2007-10-21)
		Bell called his invention the "photophone" and said it was fundamentally a greater invention than the telephone.
		Bell's photophones used a selenium detector in series with a battery and telephone receiver.
		This photophone receiver uses a silicon solar cell so no lens is necessary.
	www.curlysurmudgeon.com /gbppr/mil/sun (260 words)

	Sample Student Patent Application
		Improving upon Alexander Graham Bell's photophone patent, the proposed design claims a mechanism for transmitting sound waves through variation in intensity of light rays.
		The communications devices described in the aforementioned documents operate upon the principle of using air vibrations to produce an undulating current in a transmission device, this current being sent to a receiver, whereupon it is translated into its previous state.
		The device which most relates to our design, the photophone, uses light as a means for the conversion of these vibrations into electrical energy.
	cti.itc.virginia.edu /~meg3c/classes/tcc315_old/photoexe1.html (1302 words)

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