Paris is the capital and most populous city of France, with an area of 105 square kilometres and an official estimated population of 2,140,526 residents as of 1 January 2019. Since the 17th century, Paris has been one of Europe's major centres of finance, commerce, fashion and the arts; the City of Paris is the centre and seat of government of the Île-de-France, or Paris Region, which has an estimated official 2019 population of 12,213,364, or about 18 percent of the population of France. The Paris Region had a GDP of €681 billion in 2016, accounting for 31 percent of the GDP of France, was the 5th largest region by GDP in the world. According to the Economist Intelligence Unit Worldwide Cost of Living Survey in 2018, Paris was the second most expensive city in the world, after Singapore, ahead of Zurich, Hong Kong and Geneva. Another source ranked Paris as most expensive, on a par with Singapore and Hong-Kong, in 2018; the city is a major rail and air-transport hub served by two international airports: Paris-Charles de Gaulle and Paris-Orly.
Opened in 1900, the city's subway system, the Paris Métro, serves 5.23 million passengers daily, is the second busiest metro system in Europe after Moscow Metro. Gare du Nord is the 24th busiest railway station in the world, the first located outside Japan, with 262 million passengers in 2015. Paris is known for its museums and architectural landmarks: the Louvre was the most visited art museum in the world in 2018, with 10.2 million visitors. The Musée d'Orsay and Musée de l'Orangerie are noted for their collections of French Impressionist art, the Pompidou Centre Musée National d'Art Moderne has the largest collection of modern and contemporary art in Europe; the historical district along the Seine in the city centre is classified as a UNESCO Heritage Site. Popular landmarks in the centre of the city include the Cathedral of Notre Dame de Paris and the Gothic royal chapel of Sainte-Chapelle, both on the Île de la Cité. Paris received 23 million visitors in 2017, measured by hotel stays, with the largest numbers of foreign visitors coming from the United States, the UK, Germany and China.
It was ranked as the third most visited travel destination in the world in 2017, after Bangkok and London. The football club Paris Saint-Germain and the rugby union club Stade Français are based in Paris; the 80,000-seat Stade de France, built for the 1998 FIFA World Cup, is located just north of Paris in the neighbouring commune of Saint-Denis. Paris hosts the annual French Open Grand Slam tennis tournament on the red clay of Roland Garros. Paris will host the 2024 Summer Olympics; the 1938 and 1998 FIFA World Cups, the 2007 Rugby World Cup, the 1960, 1984, 2016 UEFA European Championships were held in the city and, every July, the Tour de France bicycle race finishes there. The name "Paris" is derived from the Celtic Parisii tribe; the city's name is not related to the Paris of Greek mythology. Paris is referred to as the City of Light, both because of its leading role during the Age of Enlightenment and more because Paris was one of the first large European cities to use gas street lighting on a grand scale on its boulevards and monuments.
Gas lights were installed on the Place du Carousel, Rue de Rivoli and Place Vendome in 1829. By 1857, the Grand boulevards were lit. By the 1860s, the boulevards and streets of Paris were illuminated by 56,000 gas lamps. Since the late 19th century, Paris has been known as Panam in French slang. Inhabitants are known in French as Parisiens, they are pejoratively called Parigots. The Parisii, a sub-tribe of the Celtic Senones, inhabited the Paris area from around the middle of the 3rd century BC. One of the area's major north–south trade routes crossed the Seine on the île de la Cité; the Parisii minted their own coins for that purpose. The Romans began their settlement on Paris' Left Bank; the Roman town was called Lutetia. It became a prosperous city with a forum, temples, an amphitheatre. By the end of the Western Roman Empire, the town was known as Parisius, a Latin name that would become Paris in French. Christianity was introduced in the middle of the 3rd century AD by Saint Denis, the first Bishop of Paris: according to legend, when he refused to renounce his faith before the Roman occupiers, he was beheaded on the hill which became known as Mons Martyrum "Montmartre", from where he walked headless to the north of the city.
Clovis the Frank, the first king of the Merovingian dynasty, made the city his capital from 508. As the Frankish domination of Gaul began, there was a gradual immigration by the Franks to Paris and the Parisian Francien dialects were born. Fortification of the Île-de-la-Citie failed to avert sacking by Vikings in 845, but Paris' strategic importance—with its bridges prevent
A patent is a form of intellectual property. A patent gives its owner the right to exclude others from making, using and importing an invention for a limited period of time twenty years; the patent rights are granted in exchange for an enabling public disclosure of the invention. In most countries patent rights fall under civil law and the patent holder needs to sue someone infringing the patent in order to enforce his or her rights. In some industries patents are an essential form of competitive advantage; the procedure for granting patents, requirements placed on the patentee, the extent of the exclusive rights vary between countries according to national laws and international agreements. However, a granted patent application must include one or more claims that define the invention. A patent may include many claims; these claims must meet relevant patentability requirements, such as novelty and non-obviousness. Under the World Trade Organization's TRIPS Agreement, patents should be available in WTO member states for any invention, in all fields of technology, provided they are new, involve an inventive step, are capable of industrial application.
There are variations on what is patentable subject matter from country to country among WTO member states. TRIPS provides that the term of protection available should be a minimum of twenty years; the word patent originates from the Latin patere, which means "to lay open". It is a shortened version of the term letters patent, an open document or instrument issued by a monarch or government granting exclusive rights to a person, predating the modern patent system. Similar grants included land patents, which were land grants by early state governments in the USA, printing patents, a precursor of modern copyright. In modern usage, the term patent refers to the right granted to anyone who invents something new and non-obvious; some other types of intellectual property rights are called patents in some jurisdictions: industrial design rights are called design patents in the US, plant breeders' rights are sometimes called plant patents, utility models and Gebrauchsmuster are sometimes called petty patents or innovation patents.
The additional qualification utility patent is sometimes used to distinguish the primary meaning from these other types of patents. Particular species of patents for inventions include biological patents, business method patents, chemical patents and software patents. Although there is some evidence that some form of patent rights was recognized in Ancient Greece in the Greek city of Sybaris, the first statutory patent system is regarded to be the Venetian Patent Statute of 1474. Patents were systematically granted in Venice as of 1474, where they issued a decree by which new and inventive devices had to be communicated to the Republic in order to obtain legal protection against potential infringers; the period of protection was 10 years.. As Venetians emigrated, they sought similar patent protection in their new homes; this led to the diffusion of patent systems to other countries. The English patent system evolved from its early medieval origins into the first modern patent system that recognised intellectual property in order to stimulate invention.
By the 16th century, the English Crown would habitually abuse the granting of letters patent for monopolies. After public outcry, King James I of England was forced to revoke all existing monopolies and declare that they were only to be used for "projects of new invention"; this was incorporated into the Statute of Monopolies in which Parliament restricted the Crown's power explicitly so that the King could only issue letters patent to the inventors or introducers of original inventions for a fixed number of years. The Statute became the foundation for developments in patent law in England and elsewhere. Important developments in patent law emerged during the 18th century through a slow process of judicial interpretation of the law. During the reign of Queen Anne, patent applications were required to supply a complete specification of the principles of operation of the invention for public access. Legal battles around the 1796 patent taken out by James Watt for his steam engine, established the principles that patents could be issued for improvements of an existing machine and that ideas or principles without specific practical application could legally be patented.
Influenced by the philosophy of John Locke, the granting of patents began to be viewed as a form of intellectual property right, rather than the obtaining of economic privilege. The English legal system became the foundation for patent law in countries with a common law heritage, including the United States, New Zealand and Australia. In the Thirteen Colonies, inventors could obtain patents through petition to a given colony's legislature. In 1641, Samuel Winslow was granted the first patent in North America by the Massachusetts General Court for a new process for making salt; the modern French patent system was created during the Revolution in 1791. Patents were granted without examination. Patent costs were high. Importation patents protected new devices coming from foreign countries; the patent law was revised in 1844 - patent cost was lowered and importation patents were abolished. The first Patent Act of the U. S. Congress was passed on April 10, 1790, titled "An Act to promote the progress of
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency. This frequency is used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, to stabilize frequencies for radio transmitters and receivers; the most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators, but other piezoelectric materials including polycrystalline ceramics are used in similar circuits. A crystal oscillator one using a quartz crystal, works by distorting the crystal with an electric field, when voltage is applied to an electrode near or on the crystal; this property is known as inverse piezoelectricity. When the field is removed, the quartz - which oscillates in a precise frequency - generates an electric field as it returns to its previous shape, this can generate a voltage.
The result is that a quartz crystal behaves like an RLC circuit, but with a much higher Q. Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz. More than two billion crystals are manufactured annually. Most are used for consumer devices such as wristwatches, radios and cellphones. Quartz crystals are found inside test and measurement equipment, such as counters, signal generators, oscilloscopes. A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric resonator, a crystal, as its frequency-determining element. Crystal is the common term used in electronics for the frequency-determining component, a wafer of quartz crystal or ceramic with electrodes connected to it. A more accurate term for it is piezoelectric resonator. Crystals are used in other types of electronic circuits, such as crystal filters. Piezoelectric resonators are sold as separate components for use in crystal oscillator circuits. An example is shown in the picture.
They are often incorporated in a single package with the crystal oscillator circuit, shown on the righthand side. Piezoelectricity was discovered by Jacques and Pierre Curie in 1880. Paul Langevin first investigated quartz resonators for use in sonar during World War I; the first crystal-controlled oscillator, using a crystal of Rochelle salt, was built in 1917 and patented in 1918 by Alexander M. Nicholson at Bell Telephone Laboratories, although his priority was disputed by Walter Guyton Cady. Cady built the first quartz crystal oscillator in 1921. Other early innovators in quartz crystal oscillators include Louis Essen. Quartz crystal oscillators were developed for high-stability frequency references during the 1920s and 1930s. Prior to crystals, radio stations controlled their frequency with tuned circuits, which could drift off frequency by 3–4 kHz. Since broadcast stations were assigned frequencies only 10 kHz apart, interference between adjacent stations due to frequency drift was a common problem.
In 1925, Westinghouse installed a crystal oscillator in its flagship station KDKA, by 1926, quartz crystals were used to control the frequency of many broadcasting stations and were popular with amateur radio operators. In 1928, Warren Marrison of Bell Telephone Laboratories developed the first quartz-crystal clock. With accuracies of up to 1 second in 30 years, quartz clocks replaced precision pendulum clocks as the world's most accurate timekeepers until atomic clocks were developed in the 1950s. Using the early work at Bell Labs, AT&T established their Frequency Control Products division spun off and known today as Vectron International. A number of firms started producing quartz crystals for electronic use during this time. Using what are now considered primitive methods, about 100,000 crystal units were produced in the United States during 1939. Through World War II crystals were made from natural quartz crystal all from Brazil. Shortages of crystals during the war caused by the demand for accurate frequency control of military and naval radios and radars spurred postwar research into culturing synthetic quartz, by 1950 a hydrothermal process for growing quartz crystals on a commercial scale was developed at Bell Laboratories.
By the 1970s all crystals used in electronics were synthetic. In 1968, Juergen Staudte invented a photolithographic process for manufacturing quartz crystal oscillators while working at North American Aviation that allowed them to be made small enough for portable products like watches. Although crystal oscillators still most use quartz crystals, devices using other materials are becoming more common, such as ceramic resonators. A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a ordered, repeating pattern extending in all three spatial dimensions. Any object made of an elastic material could be used like a crystal, with appropriate transducers, since all objects have natural resonant frequencies of vibration. For example, steel is elastic and has a high speed of sound, it was used in mechanical filters before quartz. The resonant frequency depends on size, shape and the speed of sound in the material. High-frequency crystals are cut in the shape of a simple rectangle or circular disk.
Low-frequency crystals, such as those used in digital watches, are cut in the shape of a tuning fork. For applications not needing precise timing, a low-cost ceramic resonator is used in place of a quartz crystal; when a crystal of quartz is properly cut and mounted, it can be made to distort in an electric field by applying a vol
The Japan Times
The Japan Times is Japan's largest and oldest English-language daily newspaper. It is published by The Japan Times, Ltd. a subsidiary of News2u Holdings, Inc.. It is headquartered in the Kioicho Building in Kioicho, Tokyo; the Japan Times was launched by Motosada Zumoto on March 22, 1897, with the goal of giving Japanese an opportunity to read and discuss news and current events in English to help Japan to participate in the international community. The paper was independent of government control, but from 1931 onward, the Japanese government was mounting pressure on the paper's editors to submit to its policies. In 1933, the Japanese Ministry of Foreign Affairs managed to appoint Hitoshi Ashida, former Ministry official, as chief editor. During World War II, the newspaper served as an outlet for Imperial Japanese government propaganda and editorial opinion; the paper's circulation at that time was about 825,000. It was successively renamed The Japan Times and Mail following its merger with The Japan Mail, The Japan Times and Advertiser following its merger with The Japan Advertiser, Nippon Times before reverting to the Japan Times title in 1956.
The temporary change to Nippon Times occurred during ban of English language sentiment during World War II era Japan. Shintaro Fukushima became the president in 1956, he exchanged each company's stock with Toshiaki Ogasawara. After Fukushima renounced managing rights, Ogasawara's company Nifco, a manufacturer of automotive fasteners, acquired control of The Japan Times in 1983 and changed all of former staffs and company's tradition established in 1897. Nifco chairman Toshiaki Ogasawara served as the chairman and publisher of The Japan Times until 2016, his daughter Yukiko Ogasawara was president of the company from 2006 to 2012, when she was replaced by career Japan Times staffer Takeharu Tsutsumi. Yukiko succeeded her father as chairman of the company in 2016. Nifco sold The Japan Times to News2u Holdings, Inc. on June 30, 2017. After being sold to the "PR company" News2u, the Japan Times changed its editorial stance and contributor lineup as part of efforts to reduce criticism of the paper as an "anti-Japanese" outlet.
In November 2018, the newspaper announced in an editor's note that it would replace the term "forced labor" with "wartime laborers", the term "comfort women" with "women who worked in wartime brothels, including those who did so against their will, to provide sex to Japanese soldiers", in its subsequent articles. The change drew immediate criticism from readers and employees, with particular concerns expressed over the paper's apparent alignment with the political positions of Prime Minister Shinzō Abe; the Japan Times, Inc. publishes three periodicals: The Japan Times, an English-language daily broadsheet. The daily's content includes: News: domestic and world news. Opinion: editorials, op-eds, letters to the editor. Features: life and style, media, technology and drink, environment, cartoons. Entertainment: film, music, books, event previews, festival listing. Sports: domestic and overseas sports news, including coverage of baseball, basketball, figure skating. Since 16 October 2013, The Japan Times has been printed and sold along with The New York Times International Edition.
Printed stories from The Japan Times are archived online. The newspaper has a reader's forum and, since 2013, the website offers a section for readers' comments below articles; this came about during a redesign and redevelopment of the newspaper, using Responsive Web Design techniques so the site is optimised for all digital devices. The Japan Times has a social media presence on Twitter and Google+. Monty DiPietro, art critic John Gauntner, Nihonshu columnist Don Maloney Dreux Richard, African community, investigative Donald Richie, film critic Edward Seidensticker Robert Yellin Ceramic Scene columnist Jean Pearce, Community columnist Fred Varcoe, Sports editor Elyse Rogers and Fume Miyatake, Women in Business Columnists Mark Brazil, "Wild Watch" nature columnist Staff at The Japan Times are represented by two unions, one of, Tozen. Capital: ¥100,000,000 Business: Publishes The Japan Times, The Japan Times On Sunday, The Japan Times Alpha, books in English and Japanese Genki: an Integrated Course in Elementary Japanese A Dictionary of Basic Japanese Grammar Yomiuri Shimbun International Herald Tribune Asahi Shimbun Media related to The Japan Times at Wikimedia Commons The Japan Times Online The Japan Times Plus The Japan Times Bookclub Genki Online
In horology, a movement known as a caliber, is the mechanism of a watch or timepiece, as opposed to the case, which encloses and protects the movement, the face, which displays the time. The term originated with mechanical timepieces, whose clockwork movements are made of many moving parts, it is less applied to modern electronic or quartz timepieces, where the word module is used instead. In modern mass-produced clocks and watches, the same movement is inserted into many different styles of case; when buying a quality pocketwatch from the mid-19th to the mid-20th century, for example, the customer would select movement and case individually. Mechanical movements get dirty and the lubricants dry up, so they must periodically be disassembled and lubricated. One source recommends servicing intervals of: 3–5 years for watches, 15–20 years for grandfather clocks, 10–15 years for wall or mantel clocks, 15–20 years for anniversary clocks, 7 years for cuckoo clocks, with the longer intervals applying to antique timepieces.
A mechanical movement contains all the moving parts of a watch or clock except the hands, in the case of pendulum clocks, the pendulum and driving weights. The movement is made of the following components: Power source Either a mainspring, or a weight suspended from a cord wrapped around a pulley; the mainspring or pulley has a mechanism to allow it to be wound up, which includes a ratchet to prevent it from unwinding. The barrel or pulley has gear teeth on it. Wheel train A gear train. Large gears known as wheels mesh with small gears known as pinions; the wheels in a typical going train are the centre wheel, third wheel, fourth wheel. A separate set of wheels, the motion work, divides the motion of the minute hand by 12 to move the hour hand and in watches another set, the keyless work, allows the hands to be set. Escapement A mechanism that allows the wheel train to advance, or escape a fixed amount with each swing of the balance wheel or pendulum, it consists of a gear called an escape wheel, released one tooth at a time by a lever that rocks back and forth.
Each time the escape wheel moves forward it gives the pendulum or balance wheel a push to keep it moving. Oscillator The timekeeping element, either a pendulum or a balance wheel, it swings back and forth, with a constant time interval between each swing, called the beat. A pendulum movement has a pendulum hangar attached to a sturdy support on the back, from which the pendulum is suspended and a fork which gives the pendulum impulses; the oscillator always has some means for adjusting the rate of the clock. Pendulums have an adjustment nut under the bob, while balance wheels have a regulator lever on the balance spring. Watch movements come in various shapes to fit different case styles, such as round, rectangular, rectangular with cut corners and baguette, are measured in lignes, or in millimetres; each specific watch movement is called a caliber. The movement parts are separated into two main categories: those belonging to the ébauches and those belonging to the assortments. In watch movements the wheels and other moving parts are mounted between two plates, which are held a small distance apart with pillars to make a rigid framework for the movement.
One of these plates, the front plate just behind the face, is always circular, or the same shape and dimensions as the movement. The back plate has various shapes: Full plate movement In this design, used in the earliest pocketwatches until the 18th century, the back plate was circular. All the parts of the watch were mounted between the two plates except the balance wheel, mounted on the outside of the back plate, held by a bracket called the balance cock. Three-quarter plate movement In the 18th century, to make movements thinner, part of the back plate was cut away to make room for the balance and balance cock. Bridge movement In modern watch movements, the back plate is replaced with a series of plates or bars, called bridges; this makes servicing the movement easier, since individual bridges and the wheels they support can be removed and installed without disturbing the rest of the movement. The first bridge movements, in Swiss pocketwatches from around 1900, had three parallel bar bridges to support the three wheels of the going train.
This style is called Geneva movement. Mechanical watch movements are classified as manual or automatic: Manual or hand winding In this type the wearer must turn the crown periodically daily, in order to wind the mainspring, storing energy to run the watch until the next winding. Automatic or self-winding In this type, used in most mechanical watches sold today, the mainspring is automatically wound by the natural motions of the wearer's wrist while it is being worn, eliminating the need for manual winding. Additionally, a distinction is sometimes made on whether or not the movement offers hacking, allowing the second hand to be stopped. In horology, "caliber" refers to the specific internal mechanism of a watch or clock known as a movement. Although the term was only used to refer to the size of a movement, it is now used to designate a specific model. Different watch manufacturers tend to use their own identification system to number their calibers. Clockwork Chinese standard movement Spring Drive Federation of the Swiss Watch Industry: Glossary Easy Guide to Watch Movements Caliber Guide
Seikosha was a branch of the Japanese company Seiko that produced clocks, shutters, computer printers and other devices. It was the root of the manufacturing companies of the Seiko Group. 1881 — Kintarō Hattori opens the watch and jewelry shop "K. Hattori" in the Ginza area of Tokyo, Japan. 1892 — Seikosha is established in Tokyo as the clock manufacturing arm of K. Hattori. 1917 — K. Hattori becomes a company. 1937 — The watch production division of Seikosha is split off as Daini Seikosha Co. Ltd.. 1942 — Daiwa Kogyo, Ltd. is founded in Suwa, Nagano by Hisao Yamazaki. 1943 — Daini Seikosha establishes a factory in Suwa for manufacturing watches with Daiwa Kogyo. 1959 — Daiwa Kogyo and the Suwa Plant of Daini Seikosha merge to form Suwa Seikosha Co. Ltd. 1961 — Shinshu Seiki Co. Ltd. is established as a subsidiary of Suwa Seikosha. 1970 — Seikosha is split off from K. Hattori & Co. Ltd. and Seikosha Co. Ltd. is incorporated. 1982 — K. Hattori & Co. Ltd. is renamed Hattori Seiko Co. Ltd. 1982 — Shinshu Seiki is renamed Epson Corporation.
1983 — Daini Seikosha is renamed Seiko Instruments & Electronics Ltd. 1985 — Suwa Seikosha and Epson merge to form Seiko Epson Corporation. 1990 — Hattori Seiko Co. Ltd. is renamed Seiko Corporation. 1996 — Seikosha Co. Ltd. is divided into Seiko Precision Inc. and Seiko Clock Inc. 1997 — Seiko Instruments & Electronics is renamed Seiko Instruments Inc. 2007 — Seiko Corporation is renamed Seiko Holdings Corporation. 1 October 2009 — Seiko Instruments becomes a wholly owned subsidiary of Seiko Holdings. Seikosha website Seiko Holdings Corporation Seiko Clock Inc. Seiko Precision Inc. Seiko Instruments Inc. Seiko Epson Corporation
A balance wheel, or balance, is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral torsion spring, the balance spring or hairspring, it is driven by the escapement, which transforms the rotating motion of the watch gear train into impulses delivered to the balance wheel. Each swing of the wheel allows the gear train moving the hands forward; the balance wheel and hairspring together form a harmonic oscillator, which due to resonance oscillates preferentially at a certain rate, its resonant frequency or'beat', resists oscillating at other rates. The combination of the mass of the balance wheel and the elasticity of the spring keep the time between each oscillation or ‘tick’ constant, accounting for its nearly universal use as the timekeeper in mechanical watches to the present. From its invention in the 14th century until tuning fork and quartz movements became available in the 1960s every portable timekeeping device used some form of balance wheel.
Until the 1980s balance wheels were the timekeeping technology used in chronometers, bank vault time locks, time fuzes for munitions, alarm clocks, kitchen timers and stopwatches, but quartz technology has taken over these applications, the main remaining use is in quality mechanical watches. Modern watch balance wheels are made of Glucydur, a low thermal expansion alloy of beryllium and iron, with springs of a low thermal coefficient of elasticity alloy such as Nivarox; the two alloys are matched so their residual temperature responses cancel out, resulting in lower temperature error. The wheels are smooth, to reduce air friction, the pivots are supported on precision jewel bearings. Older balance wheels used weight screws around the rim to adjust the poise, but modern wheels are computer-poised at the factory, using a laser to burn a precise pit in the rim to make them balanced. Balance wheels rotate about 1½ turns with each swing, that is, about 270° to each side of their center equilibrium position.
The rate of the balance wheel is adjusted with the regulator, a lever with a narrow slit on the end through which the balance spring passes. This holds the part of the spring behind the slit stationary. Moving the lever slides the slit up and down the balance spring, changing its effective length, thus the resonant vibration rate of the balance. Since the regulator interferes with the spring's action and some precision watches have ‘free sprung’ balances with no regulator, such as the Gyromax, their rate is adjusted by weight screws on the balance rim. A balance's vibration rate is traditionally measured in beats per hour, or BPH, although beats per second and Hz are used; the length of a beat is one swing of the balance wheel, between reversals of direction, so there are two beats in a complete cycle. Balances in precision watches are designed with faster beats, because they are less affected by motions of the wrist. Alarm clocks and kitchen timers have a rate of 4 beats per second. Watches made prior to the 1970s had a rate of 5 beats per second.
Current watches have rates of 6, 8 and a few have 10 beats per second. During WWII, Elgin produced a precise stopwatch that ran at 40 beats per second, earning it the nickname'Jitterbug'. Audemars Piguet produces a movement that allows for a high balance vibration of 12 beats/s; the precision of the best balance wheel watches on the wrist is around a few seconds per day. The most accurate balance wheel timepieces made were marine chronometers, which were used on ships for celestial navigation, as a precise time source to determine longitude. By WWII they had achieved accuracies of 0.1 second per day. In watchmaking the term "wheel" means a large gear with teeth on its periphery – great wheel, centre wheel, third wheel, etc; the "balance wheel" has no teeth and therefore is not a wheel in this sense. Some recognise this and refer to it as the "balance". For instance Jendritzki and de Carle use the term "balance" rather than "balance wheel", it appears that the term balance wheel is used in America, although the great American watchmaker Henry Fried, described in his obituary in The New York Times as "the dean of American watchmakers" used the term balance rather than balance wheel.
A balance wheel's period of oscillation T in seconds, the time required for one complete cycle, is determined by the wheel's moment of inertia I in kilogram-meter2 and the stiffness of its balance spring κ in newton-meters per radian: T = 2 π I κ The balance wheel appeared with the first mechanical clocks, in 14th century Europe, but it seems unknown when or where it was first used. It is an improved version of the foliot, an early inertial timekeeper consisting of a straight bar pivoted in the center with weights on the ends, which oscillates back and forth; the foliot weights could be slid out on the bar, to adjust the rate of the clock. The first clocks in northern Europe used foliots, while those in southern Europe used balance wheels; as clocks were made smaller, first as bracket clocks and lantern clocks and as the first large watches after 1500, balance wheels began to be used in place of foliots. Since more of its weight is located on the rim away from the axis, a balance wheel could have a larger moment of inertia than a foliot of the same size