The development of practical fluorescent lamps took decades, and many researchers contributed. Julius Plucker and Heinrich Geissler made glowing glass tubes in the 1850s, about the time George Stokes discovered that invisible ultraviolet light made some materials glow or "fluoresce." Alexandre Edmond Becquerel put fluorescent materials in a Geissler tube in 1859, though his tubes did not last long. Carbon dioxide-filled tubes by D. McFarlan Moore and mercury vapor tubes by Peter Cooper Hewitt around 1900 gave practical experience with gas-filled, discharge lamps and inspired the neon tubes of Georges Claude.
In 1926 Friedrich Meyer, Hans Spanner, and Edmund Germer of Germany patented an enclosed glass tube containing mercury vapor, electrodes at either end, and a coating of fluorescent powders called phosphors. This incorporated all of the features we see in modern fluorescent tubes, but their employer did not pursue development. William Enfield of General Electric saw phosphor-coated neon tubes in France in the early 1930s, and heard that European researchers were developing a fluorescent lamp. An especially urgent 1934 letter from a consultant, Nobel-laureate Arthur Compton, coming on the heels of European breakthroughs in low-pressure sodium and high-pressure mercury lamps, spurred both GE and its licensee Westinghouse into combined action.
Enfield created a team led by George Inman, and by the end of 1934 they made several working fluorescent lamps, including the one seen here. To save time, the team adopted the design of an existing tubular incandescent lamp in order to make use of available production equipment and lamp parts. Speed was important. In addition to European competitors, American companies like Sylvania were also working on fluorescents. A second GE group under Philip Pritchard worked on production equipment. Other GE groups in Schenectady and in Ft. Wayne assisted in developing ballasts and resolving problems of circuit design.
In 1936 GE and Westinghouse demonstrated the new lamp to the U.S. Navy (that lamp is in the Smithsonian's collection). The public finally saw fluorescent lamps in 1939 at both the New York World's Fair and the Golden Gate Exposition in San Francisco. These early lamps gave twice the energy efficiency of the best incandescent designs. Production of fluorescent lamps, slow at first, soon soared as millions were installed in factories making equipment for the American military during World War 2.
Lamp characteristics: Double-ended without bases. Flat presses with an exhaust tip near one press. A tungsten electrode, CC-6 configuration coated with emitter, is set at either end. A mercury pellet is loose inside the lamp. The clear T-7 glass envelope has a phosphor coating covering about 3 inches (8 cm) of the lamp near the center.
In the wake of soaring energy prices in the 1970s, several manufacturers quickly introduced new lamp designs to meet a demand for efficient lighting devices. General Electric mounted a circular fluorescent tube on an adapter that housed a starter and ballast, and that could screw into an ordinary fixture. Called the Circlite, this hybrid product was introduced to the public in 1976.
Since circular fluorescent tubes were already a mature product (originally developed in 1943), GE could take advantage of existing research data and production lines for the Circlite. Also, retailers and consumers were familiar with circular lamps, which eased resistance to the introduction of the new unit. The modular design allowed users to replace the tube when it failed, without having to replace the more expensive ballast package. Ultimately, GE and other manufacturers produced several versions of the lamp and refined the product. A light-weight electronic ballast replaced the heavier, less-efficient magnetic ballast used in this 1978 model, for example. As of today Circlites remain in production.
Lamp characteristics: A modular fluorescent lamp with three components: ballast, mounting frame, and lamp. Ballast: aluminum medium-screw base with brass contact and a glass insulator. A plastic skirt houses a magnetic ballast and a receptacle for a circular fluorescent lamp frame. Mounting frame: a three-arm plastic frame (made in two halves) with a sliding switch to release the ballast. The ballast mounts at center of mounting frame. Lamp: circular fluorescent tube with soft white colored phosphor.
This reel-to-reel BK-401 “Soundmirror” used paper recording tape coated with artificial magnetite particles. Brush Company designed the BK-401 after Semi Begun’s experiments convinced him that a thin, flexible tape would give good audio performance. Introduced in 1947 with tape made by Shellmar Company, the expensive BK-401 malfunctioned easily. Despite good initial sales, production ceased in 1952.
Before leaving Nazi Germany in 1935, Begun had heard of Fritz Pfleumer’s work on printing cigarette paper with a gold-colored band. Pfleumer also made paper tape coated with magnetizable materials and fabricated a demonstration tape recorder in 1931.
Electrical to mechanical transducer in original package. Loud-speaker adapter. "Radio talking machine speaker". Marked: Unit: "Dulce-Tone / The Teagle Co. / Cleveland, O. / Pats. Pend. / Made in USA"; Box: "Radio Talking Machine Speaker / Model V / For Victor Victrolas Only". Cord about 57". Phonograph needle of an acoustical phonograph rests on a slotted metal piece which acts to convey audio signals from the electromagnet headphone-type driver unit to the diaphragm of an acoustical tone arm, which in turn conveys sound to the standard phonograph flare horn. Pin plugs on the cord attached to the Dulce-Tone unit plug into the audio output stage of a radio receiver. Original sale price $10.00 Reference: Pettingell-Andrews Catalog No. 7 (1925-26), page 53. "[This unit is an] electroacoustical coupler, designed to connect the audio output stage of a radio receiver to a standard acoustical phonograph. They were advertised as cures for the 'unsightly' loudspeaker which generally had a horn shape at this time. Basically a magnetic headphone, coupling was achieved by inserting the pickup needle into a reed on the driver."