The Invention of Television Technology
The Invention of Television Technology
It is hard for Americans in the twenty-first century to envision a world without television. According to U.S. Census Bureau statistics from 2004, 98 percent of households in the United States contain at least one TV set, and the average household has 2.4 sets. TV sets in the 2000s often have large screens (at least 32 inches across) that show high-definition color images. Cable and satellite systems, which are available to about 80 percent of U.S. homes, give viewers hundreds of programs from which to choose. Typical Americans spend more than four hours each day watching television. They depend on TV for entertainment as well as news and information, and they expect to see instantaneous, live coverage of various types of events from around the world.
Yet television is a relatively new invention. The technology that allowed people to send moving images across great distances did not become available until the 1920s, and most commercial development of TV took place after 1945. In fact, the grandparents of young people in school in 2006 can probably remember the first time they ever saw a TV set. That set almost certainly had a tiny screen (between 4 and 10 inches across) that showed grainy, black-and-white images. In the early days of TV, there were only three television networks. These networks broadcast programs only a few days each week, for an hour or two in the evening. For many years, television viewing was such a special event that people who owned TV sets often invited friends and neighbors over to watch the shows. Over the course of just a few decades, however, television has become a constant presence in people's lives and one of the most influential forces in American culture.
Dreaming of distance vision
Television did not arise out of the work of a single inventor. Instead, a number of inventors, scientists, and engineers made important contributions to the development of TV technology. Perhaps the first invention that contributed to the later development of TV was the telegraph. Introduced by Samuel Morse (1791–1872) in 1835, the telegraph allowed people to exchange coded messages by transmitting (sending) a series of tapping sounds over electrical wires. Although the telegraph did not allow for the transmission of voices or pictures, its invention opened the door to long-distance communication. The next step in the development of communication technology was the 1876 invention of the telephone by Alexander Graham Bell (1847–1922). Unlike the telegraph, which limited communication to codes made up of dots and dashes, the telephone enabled people to send live voice messages across many miles of wires.
Origins of Television Terminology
The word "television," which means "seeing at a distance," was first used to describe the futuristic technology at the 1900 World's Fair by Russian scientist Constantin Perskyi. It combined two root words of different origins: the Greek word "tele," meaning "distant," and the Latin word "visio," meaning "sight." Once television technology became a reality in the late 1920s, some critics did not like the term. The editor of the British newspaper Manchester Guardian, for instance, once famously wrote: "Television? The word is half Greek and half Latin. No good will come of it."
More complaints were heard in England in 1936, during a competition to decide what television system would be adopted as standard by the British Broadcasting Corporation (BBC). Some people claimed that, given the roots of the word, the verb "televise" should actually refer to the act of watching a program rather than the act of broadcasting one. People suggested a wide variety of alternative names that they felt better described TV technology, including radioscope, farscope, mirascope, optiphone, and lustreer.
The early days of television also saw many arguments over what to call television viewers. During the 1936 competition, for example, London newspapers generally referred to people watching the test broadcasts as "lookers" or "lookers-in." Some people felt that this term was too narrow, since people not only watched but also listened to TV. A number of alternative terms were suggested—such as perceptors, audiobservers, telegazers, teleseers, inviders, and audivists—but the simpler term "viewers" eventually caught on.
Almost as soon as the telephone was introduced, scientists began dreaming about the possibility of transmitting visual images of people, objects, and events. They referred to this exciting potential technology as distance vision or seeing at a distance. Bell himself spent time working to develop a picture phone that would enable people to see each other as they talked on the telephone. The idea of viewing live, moving pictures across a distance also captured the public's imagination during the late nineteenth century. Scientific American magazine, for instance, ran its first articles about the potential for distance vision in 1880. Futuristic cartoons of the period showed people sitting at home watching sports and current events projected on a wall or a small screen. The topic of distance vision generated so much public interest that it was featured at the 1900 World's Fair (major events held in large cities around the world that gave people an opportunity to see and experience new technologies) in Paris, France, where Russian scientist Constantin Perskyi became the first person to use the word television.
Another important step in the development of long-distance communications technology came in 1887, when Heinrich Rudolf Hertz (1857–1894) discovered radio waves. Radio waves are electromagnetic energy that travels through the air (see sidebar "Broadcasting over Radio Waves"). In 1895 a scientist named Guglielmo Marconi (1874–1937) used Hertz's discovery to develop a wireless telegraph. Also known as a radio telegraph, this invention allowed telegraph messages to be sent through the air on radio waves instead of through wires. Marconi first demonstrated his invention in 1899 by sending a message across the English Channel (a twenty-mile-wide body of water separating Great Britain and France). The wireless telegraph soon led to the development of broadcast radio, which allowed voices, music, and other sounds to be transmitted wirelessly through the air. Lee DeForest (1873–1961) demonstrated this new technology in 1908 by broadcasting from the top of the Eiffel Tower in Paris, France. Some 500 miles away listeners with radio receivers were able to hear DeForest's broadcast. It was only a matter of time before inventors figured out how to use similar technology to broadcast pictures.
Experimenting with light
While all of these inventions were paving the way for television, a number of scientists and engineers were actively trying to develop the technology to transmit moving images. The earliest efforts involved the chemical element selenium. In 1873 scientists discovered that selenium responded to variations in the intensity of light. In other words, the element's ability to conduct electricity changed depending on whether it was exposed to bright light or dim light. For several years, inventors tried to use selenium's light sensitivity to convert moving images into electrical impulses, but they eventually found that the element responded too slowly for this purpose.
In 1884 German scientist Paul G. Nipkow (1860–1940) applied for a patent (a form of legal protection that gives an inventor exclusive rights to use and market an invention for a certain number of years) on an invention he called an electric telescope. Nipkow's invention successfully scanned the light reflected by a moving image, turned it into an electrical signal, and transmitted it across a wire. His system used a set of spinning metal disks with holes arranged in a spiral pattern to scan the image. Inside each hole were photosensitive cells (cells sensitive to light) that, as the disks spun, repeatedly measured the amount of light hitting the hole. The cells then sent electrical signals that varied in strength depending on the amount of light hitting them. These signals were transmitted across a wire to a similar device at the other end, which reversed the process and turned the electrical signals back into light. The light source varied in intensity depending on the strength of the electrical signals it received and thus created a crude representation of the moving image at the other end of the wire. Nipkow's system of spinning disks provided the
Broadcasting over Radio Waves
Television broadcasting, along with all other types of wireless communication, relies upon radio waves. Radio waves are made up of electrical and magnetic energy that travels through space. These electromagnetic waves have two main characteristics: amplitude, which is a measure of the strength or height of each wave; and frequency, which is a measure of how quickly the wave repeats itself, or occurs at any given point.
Both of these characteristics of radio waves vary. Waves that are stronger, or taller, have a higher amplitude. Waves that occur more rapidly have a higher frequency. The frequency of radio waves is measured in hertz (named after the German physicist Heinrich Rudolf Hertz [1857–1894], who discovered radio waves in 1887). Using metric prefixes, the term kilohertz or KHz means one thousand hertz, while megahertz or MHz means one million hertz.
Not all electromagnetic energy takes the form of radio waves. At higher frequencies, the waves become infrared light. At even higher frequencies, they appear as visible light. At other, increasingly high frequencies, they turn into ultraviolet light and X rays. Some people are surprised to learn that the type of energy in radio waves is actually related to light rather than to sound. Radio waves occur in a continuous spectrum, like the colors of the rainbow in the spectrum of visible light. Each part of the radio spectrum provides a different frequency, or broadcast channel.
Radio waves can be used to carry many types of communication signals, including music, television programs, cellular phone calls, and wireless Internet data. In order to transmit such information from one place to another, it must be attached to the radio waves through a process called modulation. Modulating a radio wave involves changing one or both of its basic characteristics. Changing the strength of the wave is called amplitude modulation, which is commonly abbreviated AM. Changing the repetition pattern of the wave is called frequency modulation, abbreviated FM. There are many other types of modulation, but they are all variations or combinations of AM and FM. For example, one of the types that is often used to carry television broadcast signals, Vestigial Sideband (VSB), is a form of AM.
Although the spectrum of useful radio waves is large, it is not unlimited. If two radio or television stations in the same area broadcast on the same frequency, their signals may interfere with each other, causing poor reception. In order to prevent interference between different types of communication signals, the Federal Communications Commission (FCC) divides up the radio spectrum and assigns frequencies to broadcasters through a system of licenses.
foundation for mechanical television sets. Mechanical TV sets were perfected in 1926 by two independent inventors, American Charles Francis Jenkins (1867–1934) and Scotsman John Logie Baird (1888–1946).
Other scientists followed a different path to develop electronic television sets. Electronic TV systems were based on cathode rays—the light rays that were emitted when an electrical current was forced through a vacuum tube. This technology served as the foundation for modern TV (see sidebar "How TV Works"). German physicist Karl Ferdinand Braun (1850–1918) invented the first cathode ray tube in 1897. The technology was further developed a decade later by English inventor A. A. Campbell-Swinton (1863–1930) and Russian scientist Boris Rosing (1869–1933).
The two men who are arguably considered the fathers of American television—Philo T. Farnsworth (1906–1971) and Vladimir Zworykin (1889–1982)—succeeded in using cathode ray tubes to create the first working electronic television systems. Farnsworth came up with his first ideas about electronic television systems in 1921, at the age of fourteen. He later claimed that a vision of the technology appeared to him while he was plowing hay on his family's Idaho farm. He began experimenting while still in high school and demonstrated various systems for his teachers. After graduating, he gained the support of investors and created the first complete electronic TV system, which he called the Image Dissector. Farnsworth applied for a patent on his system in 1927 and demonstrated it to members of the media in San Francisco, California, the following year.
In the meantime, Zworykin immigrated to the United States from Russia, where he had worked as an assistant to Boris Rosing. After taking a research job at the electrical equipment manufacturer Westinghouse, Zworykin received a patent in 1923 for a television camera tube, which he called the Iconoscope or electric eye. He then developed a screen he called the Kinescope for displaying images captured by his electric eye. Zworykin combined the two inventions to achieve the first successful electronic transmission of images in 1925. The following year, Westinghouse management decided that there was no future in television technology. They ordered Zworykin to work on projects that they considered more valuable. Yet Zworykin remained committed to television and continued his research on his own time.
Demonstrating TV's potential
The American people in the 1920s knew very little about the early research into television systems that was taking place. Farnsworth, Zworykin, and other inventors conducted their experiments outside the public eye, and no TV sets were produced for sale at this time. Most Americans were not aware that television had become a reality until April 7, 1927, when the first public demonstration of television in the United States took place. On that day, Bell Laboratories and the U.S. Department of Commerce staged the first simultaneous long-distance transmission of a live image and voice.
The speaker was Herbert Hoover (1874–1964), who was then the secretary of commerce and later became president of the United States (served 1929–33). In his historic transmission, as quoted in The Broadcast Century, Hoover said: "Today we have, in a sense, the transmission of sight for the first time in the world's history. Human genius has now destroyed the impediment [barrier] of distance in a new respect, and in a manner hitherto [until now] unknown."
The New York Times covered the event in the following day's newspaper, under a large headline reading: "Far-off Speakers Seen as Well as Heard Here in a Test of Television." According to The Broadcast Century, the Times reported that "Herbert Hoover made a speech in Washington yesterday afternoon. An audience in New York heard him and saw him. More than 200 miles of space intervening between the speaker and his audience was annihilated [destroyed] by the television apparatus … demonstrated publicly for the first time yesterday … It was as if a photograph had suddenly come to life and begun to talk, smile, nod its head and look this way and that."
Experimental television broadcasts began the following year. In 1928 inventor Charles Francis Jenkins received the first license awarded to a television station in the United States. His station, W3XK, broadcast from Wheaton, Maryland, using a mechanical TV system. The first broadcasts were so weak that the images appeared on screen as shadowlike pictures or silhouettes. According to David E. Fisher and Marshall Jon Fisher in Tube: The Invention of Television, "the entertainment value lay solely in the miracle of seeing these flickering images in your own home, transmitted as if by magic through the air." At that time, television receiver sets were tiny and expensive. The screens were only about four inches across, and they cost the equivalent of a month's pay for an average worker. Since the only programming available consisted of test broadcasts, few people were willing to make the investment in the new technology.
The golden age of radio
Another reason that television failed to catch on right away was the growing popularity of radio. Broadcast radio originated in 1908, but its initial use was limited to sailing ships and the military. The U.S. government authorized the first commercial radio station in 1921. From that time on, radio's popularity increased rapidly, and the number of radio stations, programs, and receivers increased as well. Throughout the 1920s, in fact, Americans bought radio receiver sets as quickly as they could be manufactured. Two million sets were sold in 1925 alone, and by the end of that year one out of every six homes in the country contained a radio.
Radio became America's main source of entertainment and news. The first broadcasts originated in live performances at local radio stations. Soon two major radio networks emerged: the Columbia Broadcasting System (CBS) and the National Broadcasting Company (NBC). One of the nation's largest radio manufacturers, the Radio Corporation of America (RCA), launched NBC with much fanfare in 1926. The network's first broadcast included live coverage of a star-studded event in the grand ballroom of the Waldorf-Astoria Hotel in New York City. Featuring leading singers, orchestras, and humorists of the day, it was heard by millions of people in the city and surrounding areas.
Both NBC and CBS quickly developed large networks of local radio stations that covered much of the United States. Programs originated in the network studios in New York and were sent to local stations over telephone lines. The rapid increase in radio stations led to overcrowding of the air waves, which caused interference between stations. The U.S. government addressed this situation by passing the Radio Act of 1927, which created the Federal Radio Commission (FRC) to oversee and regulate, or control, broadcasting. The FRC took responsibility for issuing radio licenses and assigning specific broadcast frequencies (operating space on the air waves) to individual stations. "Laws of physics tell us that only a limited number of frequencies can carry [radio or] television signals," William F. Baker and George Dessart explained in Down the Tube. "That limitation brought about the Radio Act of 1927: the government, to ensure that the air waves were efficiently used in the public interest, had somehow to choose among those who wished to own stations, selecting some and rejecting others."
The Radio Act of 1927 included several requirements that had important effects on the later development of broadcast television. For instance, it required that radio stations operate in the "public interest, convenience, or necessity." In effect, the act ensured that no individual or company could own the air waves. Instead, it said that the air waves belonged to the American people, and it granted broadcasters temporary licenses to use those air waves. People with radio receivers were allowed to tune into broadcasts for free, while the stations were encouraged to pay their operating costs by selling advertising time to sponsors. All of these provisions also applied to broadcast television when it became established.
Car radios were introduced in 1927, which led to further increases in the number of listeners. By 1928 there were 677 broadcast radio stations on the air and eight million radios in use across the United States. In 1929, however, the United States entered a long period of extreme economic hardship known as the Great Depression (1929–41). Businesses failed by the thousands, and a significant percentage of Americans found themselves unemployed. At the same time, a severe dry spell hit the farmlands of the Midwest and South, leading to sharp declines in crop production and widespread food shortages.
By providing free news and entertainment to struggling Americans, radio became even more popular during the 1930s. People gathered around their radios to listen to concerts, variety shows, comedies such as "Amos 'n' Andy," and multi-part dramas. As stated in The Broadcast Century, "The principal escape for millions of homeless, hungry, and ill Americans—and for millions more on the edge of poverty—was radio."
TV technology continues to develop
Since radio seemed to fulfill Americans' needs for news and entertainment, especially during the Great Depression, many people doubted whether a market really existed for television. Despite such doubts, a number of inventors and entrepreneurs continued working to develop television technology. Frustrated by Westinghouse's negative view of television, Zworykin left the company in 1929 and took his ideas to RCA. The visionary leader of RCA at this time was David Sarnoff (1891–1971). Sarnoff had first become famous in 1912 when, as a young telegraph operator, he had supposedly picked up distress signals from the famous ocean liner Titanic as it was sinking. He was a rising executive at RCA when the company created its NBC radio network in 1926, and four years later he became president of the company.
Sarnoff understood emerging communications technologies better than most people of his day, and he eagerly agreed to support Zworykin's efforts to build an all-electronic television system. In his biography of Sarnoff, titled The General: David Sarnoff and the Rise of the Communications Industry, Kenneth Bilby called the meeting between Sarnoff and Zworykin "one of the most decisive in industrial annals [history]. It brought together television's leading inventor with the executive who would guide its development."
Unwilling to be left behind, the major radio networks got involved in early TV broadcasting. These broadcasts were considered experimental, rather than regular or commercial, until TV sets went on sale to the public in 1939. The radio networks used these broadcasts to test and improve their equipment and programming. CBS began making experimental television broadcasts in 1931, for example, and by the end of that year fifteen experimental TV stations were on the air. NBC launched its first experimental television broadcasts the following year, helping to increase the total number of experimental TV stations to thirty-eight.
The early experimental TV stations did not broadcast regularly scheduled programs. Instead, the stations usually sent out postcards to inform potential viewers of the time and date of an upcoming program. Most programs were limited to half an hour, because that was how long performers could endure standing under the hot studio lights. Since only a few people had television sets in their homes at this time, the experimental TV stations often set up receivers in public places to demonstrate the new technology.
As the number of experimental television stations grew, the U.S. government decided to step in to regulate the new form of broadcasting. The Communications Act of 1934 created the Federal Communications Commission (FCC) to oversee and regulate all types of communications, including radio, television, telephone, and telegraph. The FCC thus took over the responsibilities of the FRC and also gained new, expanded responsibilities. The Communications Act of 1934 affirmed the public ownership of air waves and free access to broadcast programming that had been granted by the Radio Act of 1927. This arrangement meant that the broadcast networks depended on paid advertisements to finance their operations.
Some critics complained about this system, claiming that it forced networks to create programming with mass appeal (of interest to the majority of people) in order to attract the large audiences required by advertisers. They argued that this limited the potential for special interest and educational programming. Some people recommended that the United States adopt the British system of broadcasting, in which all TV and radio stations were owned by the government and financed through taxes. But the National Association of Broadcasters (NAB), which represented the commercial radio and experimental TV networks, objected to this plan. Its members looked forward to making money from television broadcasting.
Television saw a number of technological improvements during the 1930s. In 1936, for instance, the first coaxial cable was laid between New York City and Philadelphia, Pennsylvania. This type of cable—which consisted of copper wire surrounded by insulation, with an aluminum covering—could be used to transmit TV, telephone, and data signals. Many years later, it would make cable television possible. The first coaxial cables had the capacity to carry one television program or 480 telephone calls (by the 1970s, according to the FCC History Project, improved coaxial cables could carry 200 television programs or 132,000 telephone calls). In 1937, brothers and physicists Russell Varian (1898–1959) and Sigurd Varian (1901–1961) introduced a high-frequency amplifier called the Klystron. Their invention is credited with vastly expanding the frequencies available for TV broadcasting.
A number of broadcasting firsts also occurred during the 1930s. TV equipment produced by both RCA and Philo Farnsworth was used to broadcast the 1936 Olympic Games in Berlin, Germany. The German government set up twenty-five large screens around the city so that residents could watch the events as they occurred. Back in the United States, 1938 saw the first telecast of a Broadway play, Rachel Crothers's Susan and God. That year also featured the first live television coverage of an unscheduled news event. An NBC mobile TV camera unit happened to be nearby when a fire broke out on Ward's Island in New York. Since the TV camera was the first on the scene, several newspapers ran photographs of television screens showing footage of the event, rather than pictures of the fire itself.
RCA pushes commercial television
By the mid-1930s, electronic television systems had basically overtaken mechanical systems as the basis for future technological development efforts. Electronic systems could scan images faster than the mechanical systems' rotating disks and thus produced clearer pictures on the TV screen. In 1935, RCA announced a million-dollar research program aimed at producing affordable electronic television systems for American homes.
David Sarnoff announced a three-part strategy to bring TV to the American people. First, RCA planned to mass-produce sets on a factory assembly line to make them affordable for consumers. Second, the company decided to expand the original programs offered on its NBC network to make TV ownership more appealing. Finally, RCA organized a major demonstration of television to expose large numbers of people to the exciting new technology.
Before Sarnoff could follow through on his plans, however, RCA had to clear up some legal complications. RCA researcher Vladimir Zworykin and independent inventor Philo Farnsworth had developed working electronic television systems independently at around the same time. Both men applied to the U.S. government for patents to protect their inventions. In 1939 the U.S. Patent Office ruled in Farnsworth's favor, granting him the legal rights to produce and market several key components of television systems. After losing the patent lawsuit, RCA was forced to pay Farnsworth a licensing fee, or royalty, in order to use his patented components in its TV sets. Paying this fee marked the first time that RCA, which was famous for its own research and development, had ever paid to use someone else's technology since the company's founding in 1919.
Once RCA gained access to Farnsworth's patents, Sarnoff put his plan into action at the 1939 World's Fair in New York. The RCA pavilion contained twelve television sets representing the various new products the company planned to sell to consumers. Each set featured a small screen that was between five and nine inches across diagonally. Some of the sets had to be hooked up to a separate radio receiver in order to provide sound.
On the first day of the fair, NBC televised opening remarks by President Franklin D. Roosevelt (1882–1945; served 1933–45). This event marked the first presidential speech ever aired on television. It was broadcast to around two hundred TV sets within a 40-mile radius of the exhibition. As the fair continued, NBC broadcast different types of programs each day to appeal to a wide audience, including puppet shows, a circus, sporting events, cooking demonstrations, and coverage of the star-studded world premiere of the movie Gone with the Wind.
RCA advertised its World Fair exhibition as the first major public demonstration of television technology. Although this was not strictly true, since experimental stations had been offering programs for a dozen years by this time, huge crowds gathered to see TV for the first time. Visitors to the RCA pavilion could even step in front of a camera and see themselves on a nearby TV set. The memorable exhibit succeeded in creating a wave of public interest in television technology.
Shortly after the World's Fair, NBC switched from experimental to regular programming. It broadcast a regular schedule of dramas, variety shows, sports, and special events over its network of local stations. CBS followed suit in 1941, airing about fifteen hours of shows per week. As the programming options improved, television sets became widely available for the first time. Eight different companies—including RCA, GE, DuMont, and Philco—offered TV sets for sale to the public in 1939. The price of the sets ranged from $200 to $600, or the equivalent of about two months' salary for an average worker. This put the technology out of reach for many consumers, since millions of Americans were still out of work due to the Great Depression. Nevertheless, about five thousand television sets were sold by the end of 1939.
TV screens go black during World War II
While commercial television made its debut, however, most Americans remained glued to their radios. By 1940 there were fifty million radios in use in the United States, and more than 80 percent of American homes contained at least one radio. Radio proved its place in people's lives the following year, when the United States became involved in World War II (1939–45). On December 7, 1941, Japanese fighter planes launched a surprise attack on the U.S. naval base at Pearl Harbor, Hawaii. The following day, President Roosevelt declared war on Japan and its allies, Germany and Italy, which had been conquering various countries in Europe for the previous two years. Some sixty-two million people—the largest audience ever up to this time—listened to Roosevelt's speech on the radio.
How TV Works
The technology that makes television sets work remained basically the same for eighty-five years after the invention of television in the 1920s. Although more sophisticated types of display screens became more popular in the early 2000s, such as liquid crystal and plasma screens, most traditional televisions continued to rely on cathode ray tubes—also known as picture tubes—to display images.
A cathode is a filament inside a sealed glass tube, similar to those found in light bulbs. When the filament is heated, it forms a vacuum, or an empty space that does not contain any matter, inside the glass tube. A cathode ray is a stream of electrons, or negatively charged particles, that pour off the cathode into the vacuum. These electrons are attracted to a positively charged terminal called an anode. The anode focuses the electrons into a tight beam and shoots them toward a flat screen at one end of the tube. The inside of the screen is coated in phosphor, a substance that emits light, or glows, when struck by the beam of radiation.
If the beam of electrons were allowed to hit the screen without any interference, it would appear as a tiny dot in the middle. Instead, the cathode ray tube is wrapped in copper wires called steering coils, which create magnetic fields inside the vacuum. One set of coils deflects the beam vertically, and another set deflects it horizontally. Electronic circuits inside the TV control the movement of the beam. These circuits cause the beam to move across the phosphor-coated screen in high-frequency patterns, effectively painting the screen with an image.
The specific image that appears on the screen depends on the instructions, or video signals, that the TV set receives from a broadcast network, cable box, satellite dish, or VCR/DVD player. A complete video signal consists of three separate parts representing picture, color, and synchronization (a signal that forces the television receiver to lock on in order to reproduce an image correctly). Every TV station is assigned a specific transmitting frequency and operating power. Stations can send their video signals through the air to television antennas (for broadcast networks), through cables to decoder boxes (for cable TV), or through satellites orbiting the earth to satellite dishes (for satellite TV).
The FCC established the first technical standards for scanning and transmitting television images in the United States in 1941, and these standards have been maintained ever since then. "Images are scanned in the television camera and reproduced in the television receiver or monitor 30 times each second," as the Museum of Broadcast Communications described in its publication "Television Technology." "Each full image, or frame, is scanned by dividing the image into 525 horizontal lines, and then sequentially scanning first all the even lines (every other line) from top to bottom creating one field, and then scanning the odd-numbered lines in the same manner creating a second field. The two fields, when combined (interlaced), create one frame. Therefore, 30 complete images or frames, each made up of two fields, are created each second."
In this way, television screens essentially display a series of still frames in rapid succession. In order to turn these still pictures into a moving image, television technology depends on a special ability of the human brain known as persistence of vision. Since the brain is not capable of processing visual images as quickly as 30 times per second, it perceives the succession of still frames on a TV screen as continuous motion.
Television development, as well as most broadcasting, came to a halt during World War II. At that time, there were twenty-three television stations in the United States, and about ten thousand TV sets had been sold. TV was not yet sophisticated enough to record live events and broadcast them across long distances, so people turned to the radio for war news. Some TV stations tried to provide special wartime programming—such as training for air-raid drills and entertainment for wounded soldiers in Veterans Administration hospitals—but these efforts did not last long. Instead, television manufacturing and broadcasting mostly stopped during the war.
When the United States entered the conflict, the government placed a variety of restrictions on businesses in the interest of national defense. The U.S. military needed a large supply of electronic parts and communications equipment, for instance, so the government converted many TV and radio assembly plants to produce these materials for the war effort. Some RCA researchers began working on a secret military project to use high-frequency radio waves to locate and track moving objects. Their successful efforts became known as radar. The government also prohibited the construction of new radio and TV stations during the war years. U.S. leaders worried that spies might use these facilities to transmit information to the enemy.
Despite such restrictions, a few notable developments in the history of television occurred during the early 1940s. In April 1941, for example, the FCC adopted its first technical standard (a set of basic rules or guidelines for all manufacturers to follow) for commercial television. This standard specified that TV sets produced in the United States would divide images into 525 horizontal lines, each of which would be scanned by the TV camera and reproduced on the TV screen thirty times per second. Despite ongoing technological developments, this standard remained in place for more than fifty years.
The national television broadcasting network structure also began to take shape during the 1940s. Until 1943, NBC operated two separate radio networks, called Red and Blue. The U.S. government claimed that this arrangement unfairly limited competition and filed a lawsuit attempting to force NBC to sell one of its networks. The case went all the way to the U.S. Supreme Court, the highest court in the United States, which ruled against NBC. NBC then sold its Blue network, which became the American Broadcasting Company (ABC). When television started growing in popularity after World War II ended in 1945, the three major radio networks also became television networks. The so-called Big Three of ABC, CBS, and NBC controlled the American broadcasting industry until the rise of cable television in the 1980s.
For More Information
Barnouw, Erik. Tube of Plenty: The Evolution of American Television. New York: Oxford University Press, 1975.
Bilby, Kenneth. The General: David Sarnoff and the Rise of the Communications Industry. New York: Harper and Row, 1986.
Calabro, Marian. Zap! A Brief History of TV. New York: Four Winds Press, 1992.
Fisher, David E., and Marshall Jon Fisher. Tube: The Invention of Television. Washington, DC: Counterpoint, 1996.
Hilliard, Robert L., and Michael C. Keith. The Broadcast Century: A Biography of American Broadcasting. Boston: Focal Press, 1992.
Schwartz, Evan I. The Last Lone Inventor: A Tale of Genius, Deceit, and the Birth of Television. New York: HarperCollins, 2002.
Stashower, Daniel. The Boy Genius and the Mogul: The Untold Story of Television. New York: Broadway Books, 2002.
Bellis, Mary. "Television History." http://inventors.about.com/library/inventors/bltelevision.htm (accessed on June 5, 2006).
Brain, Marshall. "How Television Works." How Stuff Works. http://www.howstuffworks.com/tv.htm (accessed on June 5, 2006).
Couzens, Michael. "United States: Networks." Museum of Broadcast Communications. http://www.museum.tv/archives/etv/U/htmlU/unitedstatesn/unitedstatesn.htm (accessed on June 5, 2006).
"The FCC History Project: Historical Periods in Television Technology." Federal Communications Commission. http://www.fcc.gov/omd/history/tv (accessed on June 5, 2006).
"50th Anniversary of the Wonderful World of Color," March 11, 2004. U.S. Census Bureau. http://www.census.gov (accessed on June 5, 2006).
"Pioneers of TV Technology." http://members.aol.com/aj2x/PIONRS.htm (accessed on June 5, 2006).
Runyon, Steve. "Television Technology." Museum of Broadcast Communications. http://www.museum.tv/archives/etv/T/htmlT/televisionte/televisionte.htm (accessed on June 5, 2006).
"Television History: The First 75 Years." http://www.tvhistory.tv/timeline2.htm (accessed on June 5, 2006).