The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D.C. Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell.
On June 3, 1880, Bell's assistant transmitted a wireless voice telephone message from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters (about 700 ft.) away.
Bell believed the photophone was his most important invention. Of the 18 patents granted in Bell's name alone, and the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his "greatest achievement", telling a reporter shortly before his death that the photophone was "the greatest invention [I have] ever made, greater than the telephone".
The photophone was a precursor to the fiber-optic communication systems that achieved worldwide popular usage starting in the 1980s. The master patent for the photophone (U.S. Patent 235,199 Apparatus for Signalling and Communicating, called Photophone) was issued in December 1880, many decades before its principles came to have practical applications.
The photophone was similar to a contemporary telephone, except that it used modulated light as a means of wireless transmission while the telephone relied on modulated electricity carried over a conductive wire circuit.
Bell's own description of the light modulator:
We have found that the simplest form of apparatus for producing the effect consists of a plane mirror of flexible material against the back of which the speaker's voice is directed. Under the action of the voice the mirror becomes alternately convex and concave and thus alternately scatters and condenses the light.
The brightness of a reflected beam of light, as observed from the location of the receiver, therefore varied in accordance with the audio-frequency variations in air pressure—the sound waves—which acted upon the mirror.
In its initial form, the photophone receiver was also non-electronic, using the photoacoustic effect. Bell found that many substances could be used as direct light-to-sound transducers. Lampblack proved to be outstanding. Using a fully modulated beam of sunlight as a test signal, one experimental receiver design, employing only a deposit of lampblack, produced a tone that Bell described as "painfully loud" to an ear pressed close to the device.
In its ultimate electronic form, the photophone receiver used a simple selenium cell photodetector at the focus of a parabolic mirror. The cell's electrical resistance (between about 100 and 300 ohms) varied inversely with the light falling upon it, i.e., its resistance was higher when dimly lit, lower when brightly lit. The selenium cell took the place of a carbon microphone—also a variable-resistance device—in the circuit of what was otherwise essentially an ordinary telephone, consisting of a battery, an electromagnetic earphone, and the variable resistance, all connected in series. The selenium modulated the current flowing through the circuit, and the current was converted back into variations of air pressure—sound—by the earphone.
In his speech to the American Association for the Advancement of Science in August 1880, Bell gave credit for the first demonstration of speech transmission by light to Mr. A.C. Brown of London in the Fall of 1878.
Because the device used radiant energy, the French scientist Ernest Mercadier suggested that the invention should not be named 'photophone', but 'radiophone', as its mirrors reflected the Sun's radiant energy in multiple bands including the invisible infrared band. Bell used the name for a while but it should not be confused with the later invention "radiophone" which used radio waves.
While honeymooning in Europe with his bride Mabel Hubbard, Bell likely read of the newly discovered property of selenium having a variable resistance when acted upon by light, in a paper by Robert Sabine as published in Nature on 25 April 1878. In his experiments, Sabine used a meter to see the effects of light acting on selenium connected in a circuit to a battery. However Bell reasoned that by adding a telephone receiver to the same circuit he would be able to hear what Sabine could only see.
As Bell's former associate, Thomas Watson, was fully occupied as the superintendent of manufacturing for the nascent Bell Telephone Company back in Boston, Massachusetts, Bell hired Charles Sumner Tainter, an instrument maker who had previously been assigned to the U.S. 1874 Transit of Venus Commission, for his new 'L' Street laboratory in Washington, at the rate of $15 per week.
On February 19, 1880 the pair had managed to make a functional photophone in their new laboratory by attaching a set of metallic gratings to a diaphragm, with a beam of light being interrupted by the gratings movement in response to spoken sounds. When the modulated light beam fell upon their selenium receiver Bell, on his headphones, was able to clearly hear Tainter singing Auld Lang Syne.
In an April 1, 1880 Washington, D.C. experiment, Bell and Tainter communicated some 79 metres (259 ft) along an alleyway to the laboratory's rear window. Then a few months later on June 21 they succeeded in communicating clearly over a distance of some 213 meters (about 700 ft.), using plain sunlight as their light source, practical electrical lighting having only just been introduced to the U.S. by Edison. The transmitter in their latter experiments had sunlight reflected off the surface of a very thin mirror positioned at the end of a speaking tube; as words were spoken they cause the mirror to oscillate between convex and concave, altering the amount of light reflected from its surface to the receiver. Tainter, who was on the roof of the Franklin School, spoke to Bell, who was in his laboratory listening and who signaled back to Tainter by waving his hat vigorously from the window, as had been requested.
The receiver was a parabolic mirror with selenium cells at its focal point. Conducted from the roof of the Franklin School to Bell's laboratory at 1325 'L' Street, this was the world's first formal wireless telephone communication (away from their laboratory), thus making the photophone the world's earliest known voice wireless telephone systems, at least 19 years ahead of the first spoken radio wave transmissions. Before Bell and Tainter had concluded their research in order to move on to the development of the Graphophone, they had devised some 50 different methods of modulating and demodulating light beams for optical telephony.
The telephone itself was still something of a novelty, and radio was decades away from commercialization. The social resistance to the photophone's futuristic form of communications could be seen in an August 1880 New York Times commentary:
The ordinary man ... will find a little difficulty in comprehending how sunbeams are to be used. Does Prof. Bell intend to connect Boston and Cambridge ... with a line of sunbeams hung on telegraph posts, and, if so, what diameter are the sunbeams to be ....[and] will it be necessary to insulate them against the weather ... until (the public) sees a man going through the streets with a coil of No. 12 sunbeams on his shoulder, and suspending them from pole to pole, there will be a general feeling that there is something about Professor Bell's photophone which places a tremendous strain on human credulity.
However at the time of their February 1880 breakthrough, Bell was immensely proud of the achievement, to the point that he wanted to name his new second daughter "Photophone", which was subtly discouraged by his wife Mabel Bell (they instead chose "Marian", with "Daisy" as her nickname). He wrote somewhat enthusiastically:
I have heard articulate speech by sunlight! I have heard a ray of the sun laugh and cough and sing! ...I have been able to hear a shadow and I have even perceived by ear the passage of a cloud across the sun's disk. You are the grandfather of the Photophone and I want to share my delight at my success.
Bell transferred the photophone's intellectual property rights to the American Bell Telephone Company in May 1880. While Bell had hoped his new photophone could be used by ships at sea and to also displace the plethora of telephone lines that were blooming along busy city boulevards, his design failed to protect its transmissions from outdoor interferences such as clouds, fog, rain, snow and such, that could easily disrupt the transmission of light. Factors such as the weather and the lack of light inhibited the use of Bell's invention. Not long after its invention laboratories within the Bell System continued to improve the photophone in the hope that it could supplement or replace expensive conventional telephone lines. Its earliest non-experimental use came with military communication systems during World War I and II, its key advantage being that its light-based transmissions could not be intercepted by the enemy.
Bell pondered the photophone's possible scientific use in the spectral analysis of artificial light sources, stars and sunspots. He later also speculated on its possible future applications, though he did not anticipate either the laser or fiber-optic telecommunications:
Can Imagination picture what the future of this invention is to be!.... We may talk by light to any visible distance without any conduction wire.... In general science, discoveries will be make by the Photophone that are undreamed of just now.
Although Bell Telephone researchers made several modest incremental improvements on Bell and Tainter's design, Marconi's radio transmissions started to far surpass the maximum range of the photophone as early as 1897 and further development of the photophone was largely arrested until German-Austrian experiments began at the turn of the 20th century.
The German physicist Ernst Ruhmer believed that the increased sensitivity of his improved 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. Ruhmer carried out a series of experimental transmissions along the Havel river 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. He continued his experiments around Berlin through 1904, in conjunction with the German Navy, which supplied high-powered searchlights for use in the transmissions.
The German Siemens & Halske Company boosted the photophone's range by utilizing current-modulated carbon arc lamps which provided a useful range of approximately 8 kilometres (5.0 mi). They produced units commercially for the German Navy, which were further adapted to increase their range to 11 kilometres (6.8 mi) using voice-modulated ship searchlights.
British Admiralty research during WWI resulted in the development of a vibrating mirror modulator in 1916. More sensitive molybdenite receiver cells, which also had greater sensitivity to infra-red radiation, replaced the older selenium cells in 1917. The United States and German governments also worked on technical improvements to Bell's system.
By 1935 the German Carl Zeiss Company had started producing infra-red photophones for the German Army's tank battalions, employing tungsten lamps with infra-red filters which were modulated by vibrating mirrors or prisms. These also used receivers which employed lead sulfide detector cells and amplifiers, boosting their range to 14 kilometres (8.7 mi) under optimal conditions. The Japanese and Italian armies also attempted similar development of lightwave telecommunications before 1945.
Several military laboratories, including those in the United States, continued R&D efforts on the photophone into the 1950s, experimenting with high-pressure vapour and mercury arc lamps of between 500 and 2,000 watts power.
On March 3, 1947, the centenary of Alexander Graham Bell's birth, the Telephone Pioneers of America dedicated a historical marker on the side of one of the buildings, the Franklin School, which Bell and Sumner Tainter used for their first formal trial involving a considerable distance. Tainter had originally stood on the roof of the school building and transmitted to Bell at the window of his laboratory. The marker did not acknowledge Tainter's scientific and engineering contributions.
On February 19, 1980, exactly 100 years to the day after Bell and Tainter's first photophone transmission in their laboratory, staff from the Smithsonian Institution, the National Geographic Society and AT&T's Bell Labs gathered at the location of Bell's former 1325 'L' Street Volta Laboratory in Washington, D.C. for a commemoration of the event.
The Photophone Centenary commemoration had first been proposed by electronics researcher and writer Forrest M. Mims, who suggested it to Dr. Melville Bell Grosvenor, the inventor's grandson, during a visit to his office at the National Geographic Society. The historic grouping later observed the centennial of the photophone's first successful laboratory transmission by using Mims hand-made demonstration photophone, which functioned similar to Bell and Tainter's model.[Note 1]
Mims also built and provided a pair of modern hand-held battery-powered LED transceivers connected by 100 yards (91 m) of optical fiber. The Bell Labs' Richard Gundlach and the Smithsonian's Elliot Sivowitch used the device at the commemoration to demonstrate one of the photophone's modern-day descendants. The National Geographic Society also mounted a special educational exhibit in its Explorer's Hall, highlighting the photophone's invention with original items borrowed from the Smithsonian Institution.
Alexander Graham Bell ('Graham' pronounced ) (March 3, 1847 – August 2, 1922) was a Scottish-born scientist, inventor, engineer, and innovator who is credited with inventing and patenting the first practical telephone. He also founded the American Telephone and Telegraph Company (AT&T) in 1885.Bell's father, grandfather, and brother had all been associated with work on elocution and speech and both his mother and wife were deaf, profoundly influencing Bell's life's work. His research on hearing and speech further led him to experiment with hearing devices which eventually culminated in Bell being awarded the first U.S. patent for the telephone in 1876. Bell considered his invention an intrusion on his real work as a scientist and refused to have a telephone in his study.Many other inventions marked Bell's later life, including groundbreaking work in optical telecommunications, hydrofoils, and aeronautics. Although Bell was not one of the 33 founders of the National Geographic Society, he had a strong influence on the magazine while serving as the second president from January 7, 1898, until 1903.Annapolis (1928 film)
Annapolis is a 1928 silent film drama directed by Christy Cabanne. It was released with Photophone sound and effects. It stars Johnny Mack Brown, Jeanette Loff and Hugh Allan.Prints and incomplete prints exist.Captain Swagger
Captain Swagger is a 1928 American silent crime drama film directed by Edward H. Griffith and stars Rod La Rocque. The film was produced and distributed by the Pathé Exchange company. Utilizing the RCA Photophone sound-on-film sound system, the film was rereleased in the United States with talking sequences, synchronized music, and sound effects.Charles Sumner Tainter
Charles Sumner Tainter (April 25, 1854 – April 20, 1940) was an American scientific instrument maker, engineer and inventor, best known for his collaborations with Alexander Graham Bell, Chichester Bell, Alexander's father-in-law Gardiner Hubbard, and for his significant improvements to Thomas Edison's phonograph, resulting in the Graphophone, one version of which was the first Dictaphone.Later in his career Tainter was associated with the International Graphopone Company of West Virginia, and also managed his own research and development laboratory, earning him the title: 'Father Of The Talking Machine' (i.e.: father of the phonograph).Gotham Pictures Company
Gotham Pictures Company was an American movie production business established in San Antonio in 1916 during the silent film era. Marshall W. Taggart was the company's president. Property in Hot Wells, Texas near San Antonio was planned as an area to build a studio for productions. The company transitioned into the sound era and under its then president Sam Sax joined with RCA Photophone to film The Girl from the Argentine. Gotham worked with Bristolphone to wire theaters in 1928.Along with Rayart, Gotham was one of the significant independent film industry prodiction houses that operated as Hollywood's dominance was still emerging. Tiffany-Stahl was another independent studio.Movietone sound system
The Movietone sound system is an optical sound-on-film method of recording sound for motion pictures that guarantees synchronization between sound and picture. It achieves this by recording the sound as a variable-density optical track on the same strip of film that records the pictures. The initial version was capable of a frequency response of 8500 Hz. Although sound films today use variable-area tracks, any modern motion picture theater (excluding those that have transitioned to digital cinema) can play a Movietone film without modification to the projector (though if the projector's sound unit has been fitted with red LED or laser light sources, the reproduction quality from a variable density track will be significantly impaired). Movietone was one of four motion picture sound systems under development in the U.S. during the 1920s, the others being DeForest Phonofilm, Warner Brothers' Vitaphone, and RCA Photophone, though Phonofilm was primarily an early version of Movietone.Optical communication
Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880.
An optical communication system uses a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal. When electronic equipment is not employed the 'receiver' is a person visually observing and interpreting a signal, which may be either simple (such as the presence of a beacon fire) or complex (such as lights using color codes or flashed in a Morse code sequence).
Free-space optical communication has been deployed in space, while terrestrial forms are naturally limited by geography, weather and the availability of light. This article provides a basic introduction to different forms of optical communication.Optical sound
Optical sound is a means of storing sound recordings on transparent film. Originally developed for military purposes, the technology first saw widespread use in the 1920s as a sound-on-film format for motion pictures. Optical sound eventually superseded all of other sound film technologies until the advent of digital sound became the standard in cinema projection booths. Optical sound has also been used for multitrack recording and for creating effects in some musical synthesizers.Pallophotophone
The pallophotophone (coined from the Greek root words pallo, to oscillate or shake; photo, light; and phone, sound, therefore literally meaning "shaking light sound") was a photographic sound recording and playback system developed by General Electric researcher Charles A. Hoxie circa 1922. The RCA Photophone sound-on-film system for motion pictures was later derived from it.RCA Photophone
This article is for the sound-on-film technology. For the telecommunication device invented by Alexander Graham Bell and Charles Sumner Tainter, see Photophone.RCA Photophone was the trade name given to one of four major competing technologies that emerged in the American film industry in the late 1920s for synchronizing electrically recorded audio to a motion picture image. RCA Photophone was an optical sound, "variable-area" film exposure system, in which the modulated area (width) corresponded to the waveform of the audio signal. The three other major technologies were the Warner Bros. Vitaphone sound-on-disc system, as well as two "variable-density" sound-on-film systems, Lee De Forest's Phonofilm, and Fox-Case's Movietone.
When Joseph P. Kennedy and other investors merged Film Booking Offices of America (FBO) with the Keith-Albee-Orpheum theater chain and Radio Corporation of America, the resulting movie studio RKO Radio Pictures used RCA Photophone as their primary sound system. In May 1929, RKO released Syncopation, the first film made in RCA Photophone.Remote infrared audible signage
Remote infrared audible signage (RIAS) was developed by Smith-Kettlewell Eye Research Institute (as Talking SignsR) so that print-handicapped people, such as those that are blind or have low-vision, or are illiterate, foreign, or visually impaired, would be able to access the same type of information available through textual print signs within the built environment.
It consists of infrared transmitters repeatedly sending encoded spoken versions of the contents of the sign through wireless communication. An early version in 1979 called "Talking Lights" has been successfully upgraded/marketed commercially as "Talking Signs" which are being globally installed.
An associated handheld or glasses-mounted IR receiver is directionally sensitive to a direct, line-of-sight infrared light beam and orients the person by giving more positive feedback when the sign is being pointed to directly and is close.
The system has been tested and works effectively in both interior and exterior settings and does not disturb those environments because the IR beams are invisible and silent.
The principle of Alexander Graham Bell's photophone led to development of devices capable of transmitting/decoding infrared waves in systems ranging from military communications through remote control systems for televisions and computers.Roberto Landell de Moura
Father Roberto Landell de Moura (January 21, 1861 – June 30, 1928), commonly known as Roberto Landell, was a Brazilian Roman Catholic priest and inventor. He is best known for his work developing long-distance audio transmissions, using a variety of technologies, including an improved megaphone device, photophone (using light beams) and radio signals.
It was reported in June 1899 that he had successfully transmitted audio over a distance of 7 kilometers (4.3 miles), which was followed by a second, public, demonstration on June 3, 1900. A lack of technical details makes it uncertain which sending technology was being used, however, if radio signals were employed, then these would be the earliest reported audio transmissions by radio. Although Landell received patents in Brazil and the United States during the first decade of the 1900s, he was unable to procure the financial support needed to further develop his devices.Sound-on-film
Sound-on-film is a class of sound film processes where the sound accompanying a picture is physically recorded onto photographic film, usually, but not always, the same strip of film carrying the picture. Sound-on-film processes can either record an analog sound track or digital sound track, and may record the signal either optically or magnetically. Earlier technologies were sound-on-disc, meaning the film's soundtrack would be on a separate phonograph record.Syncopation (1929 film)
Syncopation is a 1929 American musical film directed by Bert Glennon and starring Barbara Bennett, Bobby Watson, and Ian Hunter, although top billing went to Fred Waring and his Pennsylvanians.
This was the second film produced by RKO Radio Pictures, but the first released by the studio, as the company's first produced film, Street Girl, was not released until August 1929. The film was made at the company's New York City studios and is based on the novel Stepping High by Gene Markey. The film was heavily marketed on its release, being the first film to be broadcast over the radio, as well as being RKO's first sound musical, and was a significant success.This film was the first made in the RCA Photophone sound-on-film process, and was an important test for Radio Corporation of America, which had invested heavily in the newly created RKO.The Delightful Rogue
The Delightful Rogue is a 1929 Pre-Code romantic adventure film produced and distributed by RKO Pictures. The film was directed by A. Leslie Pearce, with the screenplay by Wallace Smith, based on his short story, A Woman Decides. The film stars Rod La Rocque as a modern-day pirate in the south seas, as well as Rita La Roy and Charles Byer. La Rocque had been playing similar style adventurers in a few of his last silent films, and this film attempts to replicate the success of those silent adventure movies using RCA's early sound equipment, the Photophone system.This Thing Called Love (1929 film)
This Thing Called Love is a 1929 American romantic comedy film directed by Paul L. Stein and starring Edmund Lowe, Constance Bennett, Ruth Taylor, Roscoe Karns, ZaSu Pitts, and Jean Harlow. Harlow appears in a cameo role, as she was not yet famous. The film is based on the play This Thing Called Love, a Comedy in Three Acts, by Edwin J. Burke.The film was recorded in RCA Photophone and featured a two-tone Technicolor sequence. No complete copy survives, only the Technicolor sequence.Volta Laboratory and Bureau
The Volta Laboratory (also known as the "Alexander Graham Bell Laboratory", the "Bell Carriage House" and the "Bell Laboratory") and the Volta Bureau were created in Georgetown, Washington, D.C. by Alexander Graham Bell.The Volta Laboratory was founded in 1880–1881 with Charles Sumner Tainter and Bell's cousin, Chichester Bell, for the research and development of telecommunication, phonograph and other technologies.
Using funds generated by the Volta Laboratory, Bell later founded the Volta Bureau in 1887 "for the increase and diffusion of knowledge relating to the deaf", and merged with the American Association for the Promotion and Teaching of Speech to the Deaf (AAPTSD) in 1908. It was renamed as the Alexander Graham Bell Association for the Deaf in 1956 and then the Alexander Graham Bell Association for the Deaf and Hard of Hearing in 1999.Wireless
Wireless communication, or sometimes simply wireless, is the transfer of information or power between two or more points that are not connected by an electrical conductor. The most common wireless technologies use radio waves. With radio waves distances can be short, such as a few meters for Bluetooth or as far as millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. Somewhat less common methods of achieving wireless communications include the use of other electromagnetic wireless technologies, such as light, magnetic, or electric fields or the use of sound.
The term wireless has been used twice in communications history, with slightly different meaning. It was initially used from about 1890 for the first radio transmitting and receiving technology, as in wireless telegraphy, until the new word radio replaced it around 1920. The term was revived in the 1980s and 1990s mainly to distinguish digital devices that communicate without wires, such as the examples listed in the previous paragraph, from those that require wires or cables. This became its primary usage in the 2000s, due to the advent of technologies such as mobile broadband, Wi-Fi and Bluetooth.
Wireless operations permit services, such as long-range communications, that are impossible or impractical to implement with the use of wires. The term is commonly used in the telecommunications industry to refer to telecommunications systems (e.g. radio transmitters and receivers, remote controls, etc.) which use some form of energy (e.g. radio waves, acoustic energy,) to transfer information without the use of wires. Information is transferred in this manner over both short and long distances.Wireless telephone
Wireless telephone may refer to:
Cordless telephone, a telephone in which the handset is portable and communicates with the body of the phone by radio, instead of being attached by a cord
Mobile phone, a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area
Photophone, a device invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter in 1880