New York City
The City of New York called either New York City or New York, is the most populous city in the United States. With an estimated 2017 population of 8,622,698 distributed over a land area of about 302.6 square miles, New York is the most densely populated major city in the United States. Located at the southern tip of the state of New York, the city is the center of the New York metropolitan area, the largest metropolitan area in the world by urban landmass and one of the world's most populous megacities, with an estimated 20,320,876 people in its 2017 Metropolitan Statistical Area and 23,876,155 residents in its Combined Statistical Area. A global power city, New York City has been described as the cultural and media capital of the world, exerts a significant impact upon commerce, research, education, tourism, art and sports; the city's fast pace has inspired the term New York minute. Home to the headquarters of the United Nations, New York is an important center for international diplomacy.
Situated on one of the world's largest natural harbors, New York City consists of five boroughs, each of, a separate county of the State of New York. The five boroughs – Brooklyn, Manhattan, The Bronx, Staten Island – were consolidated into a single city in 1898; the city and its metropolitan area constitute the premier gateway for legal immigration to the United States. As many as 800 languages are spoken in New York, making it the most linguistically diverse city in the world. New York City is home to more than 3.2 million residents born outside the United States, the largest foreign-born population of any city in the world. In 2017, the New York metropolitan area produced a gross metropolitan product of US$1.73 trillion. If greater New York City were a sovereign state, it would have the 12th highest GDP in the world. New York is home to the highest number of billionaires of any city in the world. New York City traces its origins to a trading post founded by colonists from the Dutch Republic in 1624 on Lower Manhattan.
The city and its surroundings came under English control in 1664 and were renamed New York after King Charles II of England granted the lands to his brother, the Duke of York. New York served as the capital of the United States from 1785 until 1790, it has been the country's largest city since 1790. The Statue of Liberty greeted millions of immigrants as they came to the U. S. by ship in the late 19th and early 20th centuries and is an international symbol of the U. S. and its ideals of liberty and peace. In the 21st century, New York has emerged as a global node of creativity and entrepreneurship, social tolerance, environmental sustainability, as a symbol of freedom and cultural diversity. Many districts and landmarks in New York City are well known, with the city having three of the world's ten most visited tourist attractions in 2013 and receiving a record 62.8 million tourists in 2017. Several sources have ranked New York the most photographed city in the world. Times Square, iconic as the world's "heart" and its "Crossroads", is the brightly illuminated hub of the Broadway Theater District, one of the world's busiest pedestrian intersections, a major center of the world's entertainment industry.
The names of many of the city's landmarks and parks are known around the world. Manhattan's real estate market is among the most expensive in the world. New York is home to the largest ethnic Chinese population outside of Asia, with multiple signature Chinatowns developing across the city. Providing continuous 24/7 service, the New York City Subway is the largest single-operator rapid transit system worldwide, with 472 rail stations. Over 120 colleges and universities are located in New York City, including Columbia University, New York University, Rockefeller University, which have been ranked among the top universities in the world. Anchored by Wall Street in the Financial District of Lower Manhattan, New York has been called both the most economically powerful city and the leading financial center of the world, the city is home to the world's two largest stock exchanges by total market capitalization, the New York Stock Exchange and NASDAQ. In 1664, the city was named in honor of the Duke of York.
James's older brother, King Charles II, had appointed the Duke proprietor of the former territory of New Netherland, including the city of New Amsterdam, which England had seized from the Dutch. During the Wisconsinan glaciation, 75,000 to 11,000 years ago, the New York City region was situated at the edge of a large ice sheet over 1,000 feet in depth; the erosive forward movement of the ice contributed to the separation of what is now Long Island and Staten Island. That action left bedrock at a shallow depth, providing a solid foundation for most of Manhattan's skyscrapers. In the precolonial era, the area of present-day New York City was inhabited by Algonquian Native Americans, including the Lenape, whose homeland, known as Lenapehoking, included Staten Island; the first documented visit into New York Harbor by a European was in 1524 by Giovanni da Verrazzano, a Florentine explorer in the service of the French crown. He named it Nouvelle Angoulême. A Spanish expedition led by captain Estêvão Gomes, a Portuguese sailing for Emperor Charles V, arrived in New York Harbor in January 1525 and charted the mouth of the Hudson River, which he named Río de San Antonio.
The Padrón Rea
The Polo Grounds was the name of three stadiums in Upper Manhattan, New York City, used for professional baseball and American football from 1880 through 1963. As the name suggests, the original Polo Grounds, opened in 1876 and demolished in 1889, was built for the sport of polo. Bound on the south and north by 110th and 112th Streets and on the east and west by Fifth and Sixth Avenues, just north of Central Park, it was converted to a baseball stadium when leased by the New York Metropolitans in 1880; the third Polo Grounds, built in 1890 and renovated after a fire in 1911, is the one indicated when the Polo Grounds is referenced. It was located in Coogan's Hollow and was noted for its distinctive bathtub shape short distances to the left and right field walls, an unusually deep center field. In baseball, the original Polo Grounds was home to the New York Metropolitans from 1880 through 1885, the New York Giants from 1883 through 1888; the Giants played in the second Polo Grounds for part of the 1889 season and all of the 1890 season, at the third and fourth Polo Grounds from 1891 through 1957.
The Polo Grounds was the home field of the New York Yankees from 1913 through 1922 and the New York Mets in their first two seasons of 1962 and 1963. All four versions of the ballpark hosted; the fourth version hosted the 1934 and 1942 Major League Baseball All-Star Games. In football, the third Polo Grounds was home to the New York Brickley Giants for one game in 1921 and the New York Giants from 1925 to 1955; the New York Jets of the American Football League played at the stadium from the league's inaugural season of 1960 through 1963. Other sporting events held at the Polo Grounds included soccer and Gaelic football; the last sporting event at the Polo Grounds was a football game between the New York Jets and the Buffalo Bills on December 14, 1963. Shea Stadium replaced the Polo Grounds as the home of the Mets and Jets; the Polo Grounds was demolished over a period of four months that year and a public housing complex, known as the Polo Grounds Towers, was built on the site. The original Polo Grounds stood at 110th Street between Fifth Avenue and Sixth Avenue, directly across 110th Street from the northeast corner of Central Park.
The venue's original purpose was for the sport of polo, its name was merely descriptive, not a formal name rendered as "the polo grounds" in newspapers. The Metropolitans, an independent team of major-league caliber, was the first professional baseball team to play there, beginning in September 1880, remained the sole professional occupant through the 1882 season. At that time the Metropolitans' ownership had the opportunity to bring it into the National League, but elected instead to organize a new team, the New York Gothams — who soon came to be known as the Giants — using players from the Metropolitans and the newly defunct Troy Trojans, entered it in the National League, while bringing what remained of the Metropolitan club into the competing American Association. For this purpose the ownership built a second diamond and grandstand at the park, dividing it into eastern and western fields for use by the Giants and Metropolitans respectively. Polo Grounds I thus hosted its first Major League Baseball games in 1883 as the home stadium of two teams, the American Association Metropolitans and the National League Gothams.
The dual-fields arrangement proved unworkable because of faulty surfacing of the western field, after various other arrangements were tried, the Metropolitans and Giants alternated play on the eastern field in years until the Metropolitans moved to the St. George Cricket Grounds on Staten Island in 1886. Although the Giants would soon become the team of choice in the city, the "Mets" had a good year in 1884, they had started the season in a new facility called Metropolitan Park, which proved to be such a poor venue that they moved back to the Polo Grounds within a few weeks. Despite that bit of drama, the Mets went on to win the American Association pennant, their good fortune ran out when they faced the Providence Grays in the World Series, in which Providence pitcher Old Hoss Radbourn pitched three consecutive shutouts against them. All three games had been staged at the Polo Grounds. An early highlight of Giants' play at the Polo Grounds was Roger Connor's home run over the right-field wall and into 112th Street.
The original Polo Grounds was used not only for Polo and professional baseball, but for college baseball and football as well – by teams outside New York. The earliest known surviving image of the field is an engraving of a baseball game between Yale University and Princeton University on Decoration Day, May 30, 1882. Yale and Harvard played their traditional Thanksgiving Day football game there on November 29, 1883 and November 24, 1887. New York City was in the process of extending its street grid into uptown Manhattan in 1889. Plans for an extended West 111th Street ran through the Polo Grounds. City workers are said to have shown up one day and begun cutting through the fence to lay out the new street. With the Giants having won the National League pennant the year before, as well as the World Series there was significant sentiment in the city against the move. Governor David B. Hill, who had campaigned for office on a "home rule" pledge, vetoed it on the grounds that whatever he might think of the forced destruction of the park, the will of the city government was to be respected.
The loss of their park forced the Gia
El Ateneo Grand Splendid
El Ateneo Grand Splendid is a bookshop in Buenos Aires, Argentina. In 2008, The Guardian placed it as the second most beautiful bookshop in the world.. In 2019, it was named the "world's most beautiful bookstore" by the National Geographic. Situated on Santa Fe Avenue in Barrio Norte, the building was designed by architects Peró and Torres Armengol for impresario Max Glücksmann, opened as a theatre called Teatro Gran Splendid in May 1919; the ecleticist building features ceiling frescoes painted by the Italian artist Nazareno Orlandi and caryatids sculpted by Troiano Troiani, whose work graces the cornice along the Palacio de la Legislatura de la Ciudad de Buenos Aires. The theatre had a seating capacity of 1,050, staged a variety of performances, including appearances by the tango artists Carlos Gardel, Francisco Canaro, Roberto Firpo and Ignacio Corsini. Glücksmann started his own radio station in 1924, which broadcast from the building where his recording company, Nacional Odeón, made some of the early recordings of the great tango singers of the day.
In the late twenties the theatre was converted into a cinema, in 1929 showed the first sound films presented in Argentina. The ornate former theatre was leased by Grupo Ilhsa in February 2000. Ilhsa, through Tematika, owns El Ateneo and Yenny booksellers, as well as the El Ateneo publishing house; the building was subsequently renovated and converted into a book and music shop under the direction of architect Fernando Manzone. Following refurbishment works, the 2,000 m2 El Ateneo Grand Splendid became the group's flagship store, in 2007 sold over 700,000 books. Chairs are provided throughout the building, including the still-intact theatre boxes, where customers can dip into books before purchase, there is now a café on the back of what was once the stage; the ceiling, the ornate carvings, the crimson stage curtains, the auditorium lighting and many architectural details remain. Despite the changes, the building still retains the feeling of the grand theatre; the Guardian, a prominent British periodical, named El Ateneo Grand Splendid second in its 2008 list of the world's ten best bookshops.
In 2019, it was named the "world's most beautiful bookstore" by the National Geographic
FM broadcasting is a method of radio broadcasting using frequency modulation technology. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high-fidelity sound over broadcast radio. FM broadcasting is capable of better sound quality than AM broadcasting, the chief competing radio broadcasting technology, so it is used for most music broadcasts. Theoretically wideband AM can offer good sound quality, provided the reception conditions are ideal. FM radio stations use the VHF frequencies; the term "FM band" describes the frequency band in a given country, dedicated to FM broadcasting. Throughout the world, the FM broadcast band falls within the VHF part of the radio spectrum. 87.5 to 108.0 MHz is used, or some portion thereof, with few exceptions: In the former Soviet republics, some former Eastern Bloc countries, the older 65.8–74 MHz band is used. Assigned frequencies are at intervals of 30 kHz; this band, sometimes referred to as the OIRT band, is being phased out in many countries.
In those countries the 87.5–108.0 MHz band is referred to as the CCIR band. In Japan, the band 76–95 MHz is used; the frequency of an FM broadcast station is an exact multiple of 100 kHz. In most of South Korea, the Americas, the Philippines and the Caribbean, only odd multiples are used. In some parts of Europe and Africa, only multiples are used. In the UK odd or are used. In Italy, multiples of 50 kHz are used. In most countries the maximum permitted frequency error is specified, the unmodulated carrier should be within 2000 Hz of the assigned frequency. There are other unusual and obsolete FM broadcasting standards in some countries, including 1, 10, 30, 74, 500, 300 kHz. However, to minimise inter-channel interference, stations operating from the same or geographically close transmitter sites tend to keep to at least a 500 kHz frequency separation when closer frequency spacing is technically permitted, with closer tunings reserved for more distantly spaced transmitters, as interfering signals are more attenuated and so have less effect on neighboring frequencies.
Frequency modulation or FM is a form of modulation which conveys information by varying the frequency of a carrier wave. With FM, frequency deviation from the assigned carrier frequency at any instant is directly proportional to the amplitude of the input signal, determining the instantaneous frequency of the transmitted signal; because transmitted FM signals use more bandwidth than AM signals, this form of modulation is used with the higher frequencies used by TV, the FM broadcast band, land mobile radio systems. The maximum frequency deviation of the carrier is specified and regulated by the licensing authorities in each country. For a stereo broadcast, the maximum permitted carrier deviation is invariably ±75 kHz, although a little higher is permitted in the United States when SCA systems are used. For a monophonic broadcast, again the most common permitted. However, some countries specify a lower value for monophonic broadcasts, such as ±50 kHz. Random noise has a triangular spectral distribution in an FM system, with the effect that noise occurs predominantly at the highest audio frequencies within the baseband.
This can be offset, to a limited extent, by boosting the high frequencies before transmission and reducing them by a corresponding amount in the receiver. Reducing the high audio frequencies in the receiver reduces the high-frequency noise; these processes of boosting and reducing certain frequencies are known as pre-emphasis and de-emphasis, respectively. The amount of pre-emphasis and de-emphasis used is defined by the time constant of a simple RC filter circuit. In most of the world a 50 µs time constant is used. In the Americas and South Korea, 75 µs is used; this applies to both stereo transmissions. For stereo, pre-emphasis is applied to the left and right channels before multiplexing; the use of pre-emphasis becomes a problem because of the fact that many forms of contemporary music contain more high-frequency energy than the musical styles which prevailed at the birth of FM broadcasting. Pre-emphasizing these high frequency sounds would cause excessive deviation of the FM carrier. Modulation control devices are used to prevent this.
Systems more modern than FM broadcasting tend to use either programme-dependent variable pre-emphasis. Long before FM stereo transmission was considered, FM multiplexing of other types of audio level information was experimented with. Edwin Armstrong who invented FM was the first to experiment with multiplexing, at his experimental 41 MHz station W2XDG located on the 85th floor of the Empire State Building in New York City; these FM multiplex transmissions started in November 1934 and consisted of the main channel audio program and three subcarriers: a fax program, a synchronizing signal for the fax program and a telegraph “order” channel. These original FM multiplex subcarriers were amplitude modulated. Two musical programs, consisting of both the Red and Blue Network program feeds of the NBC Radio Network, were transmitted using the same system of subcarrier modulation as part of a studio-to-transmitter link system. In April 1935, the AM subcarriers were replaced with much improved results.
The first FM subcarrier transmissions emanating from Major Armstrong's experimental station KE2XCC at Alpine, New Jersey occurred in 1948. These transmissions consisted of two-cha
Argentina the Argentine Republic, is a country located in the southern half of South America. Sharing the bulk of the Southern Cone with Chile to the west, the country is bordered by Bolivia and Paraguay to the north, Brazil to the northeast and the South Atlantic Ocean to the east, the Drake Passage to the south. With a mainland area of 2,780,400 km2, Argentina is the eighth-largest country in the world, the fourth largest in the Americas, the largest Spanish-speaking nation; the sovereign state is subdivided into twenty-three provinces and one autonomous city, Buenos Aires, the federal capital of the nation as decided by Congress. The provinces and the capital exist under a federal system. Argentina claims sovereignty over part of Antarctica, the Falkland Islands, South Georgia and the South Sandwich Islands; the earliest recorded human presence in modern-day Argentina dates back to the Paleolithic period. The Inca Empire expanded to the northwest of the country in Pre-Columbian times; the country has its roots in Spanish colonization of the region during the 16th century.
Argentina rose as the successor state of the Viceroyalty of the Río de la Plata, a Spanish overseas viceroyalty founded in 1776. The declaration and fight for independence was followed by an extended civil war that lasted until 1861, culminating in the country's reorganization as a federation of provinces with Buenos Aires as its capital city; the country thereafter enjoyed relative peace and stability, with several waves of European immigration radically reshaping its cultural and demographic outlook. The almost-unparalleled increase in prosperity led to Argentina becoming the seventh wealthiest nation in the world by the early 20th century. Following the Great Depression in the 1930s, Argentina descended into political instability and economic decline that pushed it back into underdevelopment, though it remained among the fifteen richest countries for several decades. Following the death of President Juan Perón in 1974, his widow, Isabel Martínez de Perón, ascended to the presidency, she was overthrown in 1976 by a U.
S.-backed coup which installed a right-wing military dictatorship. The military government persecuted and murdered numerous political critics and leftists in the Dirty War, a period of state terrorism that lasted until the election of Raúl Alfonsín as President in 1983. Several of the junta's leaders were convicted of their crimes and sentenced to imprisonment. Argentina is a prominent regional power in the Southern Cone and Latin America, retains its historic status as a middle power in international affairs. Argentina has the second largest economy in South America, the third-largest in Latin America, membership in the G-15 and G-20 major economies, it is a founding member of the United Nations, World Bank, World Trade Organization, Union of South American Nations, Community of Latin American and Caribbean States and the Organization of Ibero-American States. Despite its history of economic instability, it ranks second highest in the Human Development Index in Latin America; the description of the country by the word Argentina has been found on a Venetian map in 1536.
In English the name "Argentina" comes from the Spanish language, however the naming itself is not Spanish, but Italian. Argentina means in Italian " of silver, silver coloured" borrowed from the Old French adjective argentine " of silver" > "silver coloured" mentioned in the 12th century. The French word argentine is the feminine form of argentin and derives from argent "silver" with the suffix -in; the Italian naming "Argentina" for the country implies Terra Argentina "land of silver" or Costa Argentina "coast of silver". In Italian, the adjective or the proper noun is used in an autonomous way as a substantive and replaces it and it is said l'Argentina; the name Argentina was first given by the Venetian and Genoese navigators, such as Giovanni Caboto. In Spanish and Portuguese, the words for "silver" are plata and prata and " of silver" is said plateado and prateado. Argentina was first associated with the silver mountains legend, widespread among the first European explorers of the La Plata Basin.
The first written use of the name in Spanish can be traced to La Argentina, a 1602 poem by Martín del Barco Centenera describing the region. Although "Argentina" was in common usage by the 18th century, the country was formally named "Viceroyalty of the Río de la Plata" by the Spanish Empire, "United Provinces of the Río de la Plata" after independence; the 1826 constitution included the first use of the name "Argentine Republic" in legal documents. The name "Argentine Confederation" was commonly used and was formalized in the Argentine Constitution of 1853. In 1860 a presidential decree settled the country's name as "Argentine Republic", that year's constitutional amendment ruled all the names since 1810 as valid. In the English language the country was traditionally called "the Argentine", mimicking the typical Spanish usage la Argentina and resulting from a mistaken shortening of the fuller name'Argentine Republic'.'The Argentine' fell out of fashion during the mid-to-late 20th century, now the country is referred to as "Argentina".
In the Spanish language "Argentina" is feminine, taking the feminine article "La" as the i
Argentine comics are one of the most important comic traditions internationally, the most important within Latin America, living its "Golden Age" between the 1940s and the 1960s. Soon after, in 1970, the theorist Oscar Masotta synthesized its contributions in the development of their own models of action comics, humor comics and folkloric comics and the presence of other artists; the first cartoons to appear in Argentina were editorial cartoons in political satire magazines at the end of the 19th century. These cartoons single panels evolved to multiple panel constructions with sequential action. Many used methods such as text indicating dialogue emanating from the speaker's mouth, or text below the drawings for dialogue and explanation. In the 1900s, comics continued to be political satire and commentary, but strips about normal life, called cuentos vivos began to appear. Text still appeared below each drawing with dialogue or explanation. Comics continued to be published in magazines. During this time, translations of comics from the United States, such as Cocoliche by Frederick Burr Opper, showed up in Argentina.
During the 1910s, the amount of comics made in Argentina grew by bounds. In 1912, the first Argentine comic strip proper, with speech balloons and recurring characters, Las aventuras de Viruta y Chicharrón, by Manuel Redondo, began being published in Caras y Caretas. Comics, such as Aventuras de un matrimonio aun sin bautizar, by 1917, Las diabluras de Tijereta was one of the lone strips that still put text at the bottom of each picture. Billiken, a children's magazine started in 1919 included some cartoons; the popularity of comics grew in the 1920s, children's comics gained popularity. The newspaper La Nación started publishing comics daily in 1920, comics, both foreign and domestic, were a big reason for the popularity of the newspaper Crítica. In 1928, the first publication containing comics, the magazine El Tony, began its run of more than 70 years. The'20s saw the first characters created and drawn by Dante Quinterno. In 1928 Quinterno's most important character, Patoruzú, first appeared.
The 1930s saw most important newspapers featuring comic strips. Patoruzú had its own magazine, which began publication in November 1936, it became one of the most important humor magazines of the 1940s, with a record of over 300,000 copies printed for one edition. During the late 1930s superheroes from the United States, such as Superman and Batman, began appearing in local magazines such as Pif Paf, giving a place to action comics; the Argentine comic had its golden age between the mid-1940s and the 1960s, the so-called Golden Age of Argentine Comics, when a number of foreign artists, including many Italians, arrived in Argentina following World War II. José Antonio Guillermo Divito's magazine Rico Tipo, launched on 16 November 1944, contained many comic strips and was published until 1972, it included Oscar Conti's Amarroto and many others. Intervalo magazine appeared in 1945, containing longer dialogs and text in comparison with comics edited in other houses. Patoruzito magazine appeared in 1945, containing a number of children's comics in addition to the adventures of young Paturuzú.
In 1948, local superhero Misterix got his own magazine, which included other action comics, which would become one of the most important the time period. It contained several Italian comics translated into Spanish, but that gave way to local creations; the late 1940s saw the arrival to Argentina of a circle of Italian writers and artists, which further improved the quantity and quality of the comics in Argentina. These included Mario Faustinelli, Hugo Pratt, Ivo Pavone, Dino Battaglia, who were known as the Venice Group; some Argentines, notably Alberto Breccia and Solano López, were considered honorary members of the Venice Group. A number of new publications appeared, such as Fantasía. During this decade, Héctor Oesterheld, one of the most prolific writers, Solano López created the Hora Cero magazine. Between the mid-1950s and mid-1960s, some of the most important Argentine comics were created, such as Héctor Oesterheld's El Eternauta. Another illustrator, Landrú, launched Tía Vicenta in 1957.
Prominently featuring his own political cartoons and those of colleagues such as Oski and Hermenegildo Sábat, its circulation grew to nearly half a million and became the most read magazine in Argentina before its banning order by the military government installed in 1966. Around 1960, of the 6 best selling publications, only one was foreign; the arrival of foreign publications from Mexico, with better paper and ink quality and lower prices, started a financial crisis in the Argentine comic industry, several publishers, including Oesterheld's Ediciones Frontera, had to close or be sold, which forced several artists and writers to go abroad. After the 1966 coup d'état, the comics industry suffered from both some censorship and from recurring economic downturns; the 1968 biographic graphic novel of Che Guevara by Oesterheld and Breccia was removed from circulation by the government and the originals destroyed. Never
Wireless telegraphy means transmission of telegraph signals by radio waves. Before about 1910 when radio became dominant, the term wireless telegraphy was used for various other experimental technologies for transmitting telegraph signals without wires, such as electromagnetic induction, ground conduction telegraph systems. Radiotelegraphy was the first means of radio communication, it continued to be the only type of radio transmission during the first three decades of radio, called the "wireless telegraphy era" up until World War I, when the development of amplitude modulation radiotelephony allowed sound to be transmitted by radio. In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes", which spell out text messages in Morse code. In a manual system, the sending operator taps on a switch called a telegraph key which turns the transmitter on and off, producing the pulses of radio waves. At the receiver the pulses are audible in the receiver's speaker as beeps, which are translated back to text by an operator who knows Morse code.
Radiotelegraphy was used for long distance person-to-person commercial and military text communication throughout the first half of the 20th century. It became a strategically important capability during the two world wars, since a nation without long distance radiotelegraph stations could be isolated from the rest of the world by an enemy cutting its submarine telegraph cables. Beginning about 1908, powerful transoceanic radiotelegraphy stations transmitted commercial telegram traffic between countries at rates up to 200 words per minute. Radiotelegraphy was transmitted by several different modulation methods during its history; the primitive spark gap transmitters used until 1920 transmitted damped waves, which had large bandwidth and tended to interfere with other transmissions. This type of emission was banned by 1930; the vacuum tube transmitters which came into use after 1920 transmitted code by pulses of unmodulated sinusoidal carrier wave called continuous waves, still used today. To make CW transmissions audible, the receiver requires a circuit called a beat frequency oscillator.
A third type of modulation, frequency shift keying was used by radioteletypes. Morse code radiotelegraphy was replaced by radioteletype networks in most high volume applications by World War 2. Today it is nearly obsolete, the only remaining users are the radio amateur community and some limited training by the military for emergency use. Wireless telegraphy or radiotelegraphy called CW, ICW transmission, or on-off keying, designated by the International Telecommunication Union as emission type A1A, is a radio communication method in which the sending operator taps on a switch called a telegraph key, which turns the radio transmitter on and off, producing pulses of unmodulated carrier wave of different lengths called "dots" and "dashes", which encode characters of text in Morse code. At the receiving location the code is audible in the radio receiver's earphone or speaker as a sequence of buzzes or beeps, translated back to text by an operator who knows Morse code. Although this type of communication has been replaced since its introduction over 100 years ago by other means of communication it is still used by amateur radio operators as well as some military services.
A CW coastal station, KSM, still exists in California, run as a museum by volunteers, occasional contacts with ships are made. Radio beacons in the aviation service, but as "placeholders" for commercial ship-to-shore systems transmit Morse but at slow speeds; the US Federal Communications Commission issues a lifetime commercial Radiotelegraph Operator License. This requires passing a simple written test on regulations, a more complex written exam on technology, demonstrating Morse reception at 20 words per minute plain language and 16 wpm code groups. Wireless telegraphy is still used today by amateur radio hobbyists where it is referred to as radio telegraphy, continuous wave, or just CW. However, its knowledge is not required to obtain any class of amateur license. Continuous wave radiotelegraphy is regulated by the International Telecommunication Union as emission type A1A. Efforts to find a way to transmit telegraph signals without wires grew out of the success of electric telegraph networks, the first instant telecommunication systems.
Developed beginning in the 1830s, a telegraph line was a person-to-person text message system consisting of multiple telegraph offices linked by an overhead wire supported on telegraph poles. To send a message, an operator at one office would tap on a switch called a telegraph key, creating pulses of electric current which spelled out a message in Morse code; when the key was pressed, it would connect a battery to the telegraph line, sending current down the wire. At the receiving office the current pulses would operate a telegraph sounder, a device which would make a "click" sound when it received each pulse of current; the operator at the receiving station who knew Morse code would translate the clicking sounds to text and write down the message. The ground was used as the return path for current in the telegraph circuit, to avoid having to use a second overhead wire. By the 1860s, telegraph was the standard way to send most urgent commercial and milita