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A LED lamp is a product that uses a Light-emitting diode and that is assembled into a lamp or a light bulb. LED lamps last much longer, and are more efficient than incandescent lamps. Many LED lamps are also better than fluorescent lamps.

Unlike fluorescent lamps, most LED lamps do not need to "warm up" before they emit the full amount of light.

Application

LED lamps are used for both general and special-purpose lighting. Where colored light is needed, LEDs that inherently emit light of a single color require no energy-absorbing filters.

White-light LED lamps have longer life expectancy and higher efficiency (more light for the same electricity) than most other lighting when used at the proper temperature. LED sources are compact, which gives flexibility in designing lighting fixtures and good control over the distribution of light with small reflectors or lenses. Because of the small size of LEDs, control of the spatial distribution of illumination is extremely flexible, and the light output and spatial distribution of an LED array can be controlled with no efficiency loss.

LEDs using the color-mixing principle can emit a wide range of colors by changing the proportions of light generated in each primary color. This allows full color mixing in lamps with LEDs of different colors. Unlike other lighting technologies, LED emission tends to be directional (or at least Lambertian), which can be either advantageous or disadvantageous, depending on requirements. For applications where non-directional light is required, either a diffuser is used, or multiple individual LED emitters are used to emit in different directions.

Household LED lamp

Lamp sizes and bases

LED lamps are made with standard lamp connections and shapes, such as an Edison screw base, an MR16 shape with a bi-pin base, or a GU5.3 (bi-pin cap) or GU10 (bayonet fitting) and are made compatible with the voltage supplied to the sockets. They include driver circuitry to rectify the AC power and convert the voltage to an appropriate value, usually a switched-mode power supply.

As of 2010 some LED lamps replaced higher wattage bulbs; for example, one manufacturer claimed a 16-watt LED lamp was as bright as a 150 W halogen lamp.[1] A standard general-purpose incandescent bulb emits light at an efficiency of about 14 to 17 lumens/W depending on its size and voltage. According to the European Union standard, an energy-efficient lamp that claims to be the equivalent of a 60 W tungsten lamp must have a minimum light output of 806 lumens.

Some models of LED lamps are compatible with dimmers as used for incandescent lamps. LED lamps often have directional light characteristics. These lamps are more power-efficient than compact fluorescent lamps and offer lifespans of 30,000 or more hours, reduced if operated at a higher temperature than specified. Incandescent lamps have a typical life of 1,000 hours, and compact fluorescents about 8,000 hours. The lamps maintain output light intensity well over their lifetimes. Energy Star specifications require the lamps to typically drop less than 10% after 6,000 or more hours of operation, and in the worst case not more than 15%. LED lamps are available with a variety of color properties. The purchase price is higher than most other lamps, but the higher efficiency may make total cost of ownership (purchase price plus cost of electricity and changing bulbs) lower.

Several companies offer LED lamps for general lighting purposes. The technology is improving rapidly and new energy-efficient consumer LED lamps are available.

As of 2016, in the United States, LED lamps are close to being adopted as the mainstream light source because of the falling prices and because 40 and 60 watt incandescent lamps are being phased out. In the U.S. the Energy Independence and Security Act of 2007 effectively bans the manufacturing and importing of most current incandescent lamps. LED lamps have decreased substantially in pricing and many varieties are sold with subsidized prices from local utilities.

LED tube lamps

LED tube lights are designed to physically fit in fixtures intended for fluorescent tubes. Some LED tubular lamps are intended to be a drop-in replacement into existing fixtures if appropriate ballast is used. Others require rewiring of the fixtures to remove the ballast. An LED tube lamp generally uses many individual Surface-Mounted LEDs which are directional and require proper orientation during installation as opposed to Fluorescent tube lamps which emit light in all directions around the tube. Most LED tube lights available can be used in place of T8, T10, or T12 tube designations, T8 is D26mm, T10 is D30mm, in lengths of 590 mm (23 in), 1,200 mm (47 in) and 1,500 mm (59 in).

Lighting designed for LEDs

Newer light fittings designed for LED lamps, or indeed with long-lived LEDs built-in, have been coming into use as the need for compatibility with existing fittings diminishes. Such lighting does not require each bulb to contain circuitry to operate from mains voltage.

Experiments revealed surprising performance and production of vegetables and ornamental plants under LED light sources. A large number of plant species have been assessed in greenhouse trials to make sure that the quality of biomass and biochemical ingredients of such plants is comparable with, or even higher than, those grown in field conditions. Plant performance of mint, basil, lentil, lettuce, cabbage, parsley and carrot was measured by assessing both the health and vigor of the plants and the success of the LEDs in promoting growth. Also noticed was profuse flowering of select ornamentals including primula, marigold and stock.

Light emitting diodes (LEDs) offer efficient electric lighting in desired wavelengths (red + blue) which support greenhouse production in minimum time and with high quality and quantity. As LEDs are cool, plants can be placed as close as possible to light sources without overheating or scorching. This saves a large amount of space for intense cultivation.

White LED lamps have achieved market dominance in applications where high efficiency is important at low power levels. Some of these applications include flashlights, solar-powered garden or walkway lights, and bicycle lights. Monochromatic (colored) LED lamps are now commercially used for traffic signal lamps, where the ability to emit bright monochromatic light is a desired feature, and in strings of holiday lights. LED automotive lamps are widely used for their long life and small size (allowing for multiple bulbs), improving road safety. LED lamps are also becoming popular in homes, especially for bathroom and medicine cabinet lighting.

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A LED lamp is a product that uses a Light-emitting diode and that is assembled into a lamp or a light bulb. LED lamps last much longer, and are more efficient than incandescent lamps. Many LED lamps are also better than fluorescent lamps.

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Traffic lights (or traffic signals) are lights used to control the movement of traffic. They are placed on roads at intersections and crossings. The different colors of lights tell drivers what to do.

Light cycles

Traffic lights change their colors in the same order every time. In most English-speaking countries, traffic lights usually change in this order:

1. Red light on: This tells drivers to stop.

2. Green light on: This means the driver can start driving or keep driving.

3. Yellow light on: This tells drivers to stop when it is safe to, because the light is about to turn red.

In some places, the red and yellow lights can be on the same time. In the United Kingdom, this signals that the light is about to turn green. In some parts of the United States, it signals that pedestrians can cross the road. In many places, traffic signals do not use the red and yellow lights together, and traffic lights go straight from red to green.

Garrett A. Morgan, an African-American inventor, invented one of the first traffic lights. He was one of the first people to get a patent for a traffic light.

William Potts, a police officer, invented the first traffic light with three colors.

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Traffic lights (or traffic signals) are lights used to control the movement of traffic. They are placed on roads at intersections and crossings. The different colors of lights tell drivers what to do. Traffic lights change their colors in the same order every time.

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A plastic is a material that can change its shape, so many things can be made of plastic. There are many types of plastic. Some can be shaped only when they are freshly made; then they become hard. Others can be changed by heating them up or even by melting them.

Most plastics are man-made; they do not occur in nature. Most are made from petroleum or natural gas. The process of making plastics is usually quite complicated. Most of the materials that are called plastic are polymers. Polymers are long chains of atoms bonded to one another.

People experimented with plastics based on natural polymers for a very long time. Alexander Parkes, an English inventor (1813-1890), created the earliest form of plastic in 1855. It was hard but flexible and transparent, and he called it "Parkesine."

Plastic is filling up the landfills and sometimes if you burn it, it releases toxic fumes. If we do not recycle, it becomes waste.

Plastic Formulation

Plastics are mostly petrochemicals, made from petroleum, a type of oil. Engineers refine the petroleum which goes through a heating process. It develops ethylene and propylene, which are the chemical building blocks for many plastics. These chemicals are then combined with other chemicals to produce a polymer.

Well-known plastics, and their use

Environmental effects

Most plastics are durable and degrade very slowly, as their chemical structure renders them resistant to many natural processes of degradation. There are differing estimates of how much plastic waste has been produced in the last century. By one estimate, one billion tons of plastic waste have been discarded since the 1950s. Others estimate a cumulative human production of 8.3 billion tons of plastic of which 6.3 billion tons is waste, with a recycling rate of only 9%. Much of this material may persist for centuries or longer, given the demonstrated persistence of structurally similar natural materials such as amber.

The Ocean Conservancy reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined. The rivers Yangtze, Indus, Yellow River, Hai River, Nile, Ganges, Pearl River, Amur, Niger, and the Mekong "transport 88-95% of the global [plastics] load into the sea."

The presence of plastics, particularly microplastics, within the food chain is increasing. In the 1960s microplastics were observed in the guts of seabirds, and since then have been found in increasing concentrations. The long-term effects of plastic in the food chain are poorly understood. In 2009, it was estimated that 10% of modern waste was plastic, although estimates vary according to region. Meanwhile, 50-80% of debris in marine areas is plastic.

Prior to the Montreal Protocol, CFCs were commonly used in the manufacture of polystyrene, and as such the production of polystyrene contributed to the depletion of the ozone layer.

Climate change

In 2019 a new report "Plastic and Climate" was published. According to the report plastic wiil contribute Greenhouse gases in the equivalent of 850 million tons of Carbon dioxide (CO2) to the atmosphere in 2019. In current trend, annual emissions will grow to 1.34 billion tons by 2030. By 2050 plastic could emit 56 billion tons of Greenhouse gas emissions, as much as 14 percent of the earth's remaining carbon budget.

The effect of plastics on global warming is mixed. Plastics are generally made from petroleum. If the plastic is incinerated, it increases carbon emissions; if it is placed in a landfill, it becomes a carbon sink although biodegradable plastics have caused methane emissions.

Due to the lightness of plastic versus glass or metal, plastic may reduce energy consumption. For example, packaging beverages in PET plastic rather than glass or metal is estimated to save 52% in transportation energy.

Production of plastics

Production of plastics from crude oil requires 62 to 108 MJ/Kg (taking into account the average efficiency of US utility stations of 35%). Producing silicon and semiconductors for modern electronic equipment is even more energy consuming: 230 to 235 MJ/Kg of silicon, and about 3,000 MJ/Kg of semiconductors. This is much higher than the energy needed to produce many other materials, e.g. iron (from iron ore) requires 20-25 MJ/Kg of energy, glass (from sand, etc.) 18-35 MJ/Kg, steel (from iron) 20-50 MJ/Kg, paper (from timber) 25-50 MJ/Kg.

Incineration of plastics

Controlled high-temperature incineration, above 850 °C for two seconds, performed with selective additional heating, breaks down toxic dioxins and furans from burning plastic, and is widely used in municipal solid waste incineration. Municipal solid waste incinerators also normally include flue gas treatments to reduce pollutants further. This is needed because uncontrolled incineration of plastic produces polychlorinated dibenzo-p-dioxins, a carcinogen (cancer causing chemical). The problem occurs because the heat content of the waste stream varies. Open-air burning of plastic occurs at lower temperatures, and normally releases such toxic fumes.

Pyrolytic disposal

Plastics can be pyrolyzed into hydrocarbon fuels, since plastics include hydrogen and carbon. One kilogram of waste plastic produces roughly a liter of hydrocarbon.

Decomposition of plastics

Plastics contribute to approximately 10% of discarded waste. Depending on their chemical composition, plastics and resins have varying properties related to contaminant absorption and adsorption. Polymer degradation takes much longer as a result of saline environments and the cooling effect of the sea. These factors contribute to the persistence of plastic debris in certain environments. Recent studies have shown that plastics in the ocean decompose faster than was once thought, due to exposure to sun, rain, and other environmental conditions, resulting in the release of toxic chemicals such as bisphenol A. However, due to the increased volume of plastics in the ocean, decomposition has slowed down. The Marine Conservancy has predicted the decomposition rates of several plastic products. It is estimated that a foam plastic cup will take 50 years, a plastic beverage holder will take 400 years, a disposable nappy will take 450 years, and fishing line will take 600 years to degrade.

In 2018, a survey by the Global Oceanic Environmental Survey (GOES) Foundation found that the ecosystem in seas and oceans may collapse in the next 25 years, potentially causing failure of terrestrial ecosystem and "very possibly the end of life on Earth as we know it"; the main agents of this prediction were hypothesized to be plastic, ocean acidification, and ocean pollution. In order to prevent such a catastrophe, experts have proposed a total single use plastic ban, wood burning bans while planting "as many trees as possible," "pollution-free recycling of electronics, and by 2030 all industries to be zero toxic discharge." One British scientist advocates "special protection and perservation of peat bogs, wetlands, marshlands and mangrove swamps to ensure carbon dioxide is absorbed from the atmosphere."

Microbial species capable of degrading plastics are known to science, and some are potentially useful for the disposal of certain classes of plastic waste.

In 1975 a team of Japanese scientists studying ponds containing waste water from a nylon factory, discovered a strain of Flavobacterium that digested certain byproducts of nylon 6 manufacture, such as the linear dimer of 6-aminohexanoate. Nylon 4 or polybutyrolactam can be degraded by the (ND-10 and ND-11) strands of Pseudomonas sp. found in sludge. This produced γ-aminobutyric acid (GABA) as a byproduct.

Several species of soil fungi can consume polyurethane. This includes two species of the Ecuadorian fungus Pestalotiopsis that can consume polyurethane aerobically and also in anaerobic conditions such as those at the bottom of landfills.

Methanogenic consortia degrade styrene, using it as a carbon source. Pseudomonas putida can convert styrene oil into various biodegradable polyhydroxyalkanoates.

Microbial communities isolated from soil samples mixed with starch have been shown to be capable of degrading polypropylene.

The fungus Aspergillus fumigatus effectively degrades plasticized PVC. Phanerochaete chrysosporium has been grown on PVC in a mineral salt agar. Phanerochaete chrysosporium, Lentinus tigrinus, Aspergillus niger, and Aspergillus sydowii can also effectively degrade PVC. Phanerochaete chrysosporium was grown on PVC in a mineral salt agar.

Acinetobacter has been found to partially degrade low molecular weight polyethylene oligomers. When used in combination, Pseudomonas fluorescens and Sphingomonas can degrade over 40% of the weight of plastic bags in less than three months. The thermophilic bacterium Brevibacillus borstelensis (strain 707) was isolated from a soil sample and found capable of using low-density polyethylene as a sole carbon source when incubated at 50 degrees Celsius. Pre-exposure of the plastic to ultraviolet radiation broke chemical bonds and aided biodegradation; the longer the period of UV exposure, the greater the promotion of the degradation.

Less desirably, hazardous molds have been found aboard space stations, molds that degrade rubber into a digestible form.

Several species of yeasts, bacteria, algae and lichens have been found growing on synthetic polymer artifacts in museums and at archaeological sites.

In the plastic-polluted waters of the Sargasso Sea, bacteria have been found that consume various types of plastic; however it is unknown to what extent these bacteria effectively clean up poisons rather than simply releasing them into the marine microbial ecosystem.

Plastic eating microbes also have been found in landfills.

Nocardia can degrade PET with an esterase enzyme.

The fungus Geotrichum candidum, found in Belize, has been found to consume the polycarbonate plastic found in CDs.

Phenol-formaldehyde, commonly known as bakelite, is degraded by the white rot fungus Phanerochaete chrysosporium.

The futuro house was made of fibreglass-reinforced polyesters, polyester-polyurethane, and poly(methylmethacrylate.) One such house was found to be harmfully degraded by Cyanobacteria and Archaea.

Thermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler, although the purity of the material tends to degrade with each reuse cycle. There are methods by which plastics can be broken down to a feedstock state.

The greatest challenge to the recycling of plastics is the difficulty of automating the sorting of plastic wastes, making it labor-intensive. Typically, workers sort the plastic by looking at the resin identification code, although common containers like soda bottles can be sorted from memory. Typically, the caps for PETE bottles are made from a different kind of plastic which is not recyclable, which presents additional problems for the sorting process. Other recyclable materials such as metals are easier to process mechanically. However, new processes of mechanical sorting are being developed to increase the capacity and efficiency of plastic recycling.

While containers are usually made from a single type and color of plastic, making them relatively easy to sort, a consumer product like a cellular phone may have many small parts consisting of over a dozen different types and colors of plastics. In such cases, the resources it would take to separate the plastics far exceed their value and the item is discarded. However, developments are taking place in the field of active disassembly, which may result in more product components being reused or recycled. Recycling certain types of plastics can be unprofitable as well. For example, polystyrene is rarely recycled because the process is usually not cost effective. These unrecycled wastes are typically disposed of in landfills, incinerated or used to produce electricity at waste-to-energy plants.

An early success in the recycling of plastics is Vinyloop, an industrial process to separate PVC from other materials through dissolution, filtration and separation of contaminants. A solvent is used in a closed loop to elute PVC from the waste. This makes it possible to recycle composite PVC waste, which is normally incinerated or put in a landfill. Vinyloop-based recycled PVC's primary energy demand is 46 percent lower than conventionally produced PVC. The global warming potential is 39 percent lower. This is why the use of recycled material leads to a significantly better ecological outcome. This process was used after the Olympic Games in London 2012. Parts of temporary Buildings like the Water Polo Arena and the Royal Artillery Barracks were recycled. In this way, the PVC Policy could be fulfilled, which says that no PVC waste should be left after the games had ended.

In 1988, to assist recycling of disposable items, the Plastic Bottle Institute of the U.S. Society of the Plastics Industry devised a now-familiar scheme to mark plastic bottles by plastic type. Under this scheme, a plastic container is marked with a triangle of three " chasing arrows".

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Molded plastic food replicas on display outside a restaurant in Japan

Plastic piping and firestops being installed in Ontario. Certain plastic pipes can be used in some non-combustible buildings, provided they are firestopped properly and that the flame spread ratings comply with the local building code.

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A plastic is a material that can change its shape, so many things can be made of plastic. There are many types of plastic. Some can be shaped only when they are freshly made; then they become hard. Others can be changed by heating them up or even by melting them.

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A sticky note is a small piece of paper with a strip of glue along one edge that make it "sticky," so you can stick it to things.

The most common sticky note is the Post-It, which is made by a company called 3M. In 1974 a man named Arthur Fry came up with the idea for the sticky note. He used a glue that was originally too weak to be used for anything else, so the notes would come off easy. 3M started to sell Post-Its in 1980.

In 2001, the patent for the glue that 3M uses on Post-It notes expired, so many other companies now make similar sticky notes.

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A sticky note is a small piece of paper with a strip of glue along one edge that make it "sticky," so you can stick it to things. The most common sticky note is the Post-It, which is made by a company called 3M.

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Glue is a sticky material (usually a liquid) that can stick two or more things together. Glue can be made from plant or animal parts, or it can be made from oil-based chemicals.

The first glues may have been natural liquids that come out of trees when they are cut. Later people learned to make glue by boiling animal feet, cartilage or bones. Some very strong glues were first made from fish bones, rubber or milk.

A simple glue can be made at home by mixing wheat flour and water. This glue will stick pieces of paper together. Many kinds of art can be made using glue. A collage is a work of art made by using glue to stick coloured things onto paper.

Some glues can be used to keep water out of boats, buildings or vehicles. In this case the glue may be called caulk. Some man-made materials, including wood-like materials, are made using glues to bind together small pieces of material or powders.

While many glues are safe, certain kinds of glue contain strong-smelling chemicals. Some people sniff these glues to get high. Sometimes people breathe in the vapors by mistake. This is a very bad idea because these chemicals are often poisons and may cause brain damage or illness.

Glue can also be made from rice or rice flour.

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# data[].attributes.attachment_link.description
Glue is a sticky material (usually a liquid) that can stick two or more things together. Glue can be made from plant or animal parts, or it can be made from oil-based chemicals. The first glues may have been natural liquids that come out of trees when they are cut.

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Scissors are a tool used for cutting thin material like:

Knives are better than scissors for some uses. Unlike a knife, scissors have two sharp edges. Some types of scissors, like children's scissors, are not very sharp. Children's scissors are often protected with plastic. These are called "Safety Scissors".

Scissors can be made for left-handed or right-handed people. Using scissors made for the wrong hand is very hard for most people.

There are many kinds of scissors used for cutting different materials and shapes.

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Scissors are a tool used for cutting thin material like: Knives are better than scissors for some uses. Unlike a knife, scissors have two sharp edges. Some types of scissors, like children's scissors, are not very sharp. Children's scissors are often protected with plastic. These are called "Safety Scissors".

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Eyeglasses (U.S), or spectacles (Brit.) are pieces of glass or clear plastic, called lenses, in a frame that holds them in front of someone's eyes.

Corrective lenses let some people see or read better if they have problems seeing. This is used by person who have poor eyesight. Contact lenses also help people see better.

Sunglasses are a kind of eyeglasses that keep too much sunlight from getting in people's eyes.

Some eyeglasses block blue light from a computer, game, smart phone and TV.

Eyeglasses have many models. So it may be worn for fashion.

Precursors

The use of a convex lens to form an enlarged/magnified image is discussed in Alhazen's Book of Optics (1021). Its translation into Latin from Arabic in the 12th century was instrumental to the invention of eyeglasses in 13th century Italy. Englishman Robert Grosseteste's treatise De iride ("On the Rainbow"), written between 1220 and 1235, mentions using optics to "read the smallest letters at incredible distances". A few years later in 1262, Roger Bacon is also known to have written on the magnifying properties of lenses.

Sunglasses, in the form of flat panes of smoky quartz, were used in China during the 12th century. Similarly, the Inuit have used snow goggles for eye protection. While they did not offer any corrective benefits they did improve visual acuity via the pinhole effect.

The first eyeglasses were made in Italy in about 1286, but it is not clear who the inventor was. In a sermon delivered on February 23, 1306, the Dominican friar Giordano da Pisa (ca. 1255-1311) wrote "It is not yet twenty years since there was found the art of making eyeglasses, which make for good vision... And it is so short a time that this new art, never before extant, was discovered. ... I saw the one who first discovered and practiced it, and I talked to him." Giordano's colleague Friar Alessandro della Spina of Pisa (d. 1313) was soon making eyeglasses. The Ancient Chronicle of the Dominican Monastery of St. Catherine in Pisa records: "Eyeglasses, having first been made by someone else, who was unwilling to share them, he [Spina] made them and shared them with everyone with a cheerful and willing heart." By 1301, there were guild regulations in Venice governing the sale of eyeglasses.

The earliest pictorial evidence for the use of eyeglasses is Tommaso da Modena's 1352 portrait of the cardinal Hugh de Provence reading in a scriptorium. Another early example would be a depiction of eyeglasses found north of the Alps in an altarpiece of the church of Bad Wildungen, Germany, in 1403. These early glasses had convex lenses that could correct both hyperopia (farsightedness), and the presbyopia that commonly develops as a symptom of aging. It was not until 1604 that Johannes Kepler published the first correct explanation as to why convex and concave lenses could correct presbyopia and myopia.

Early frames for glasses consisted of two magnifying glasses riveted together by the handles so that they could grip the nose. These are referred to as "rivet spectacles". The earliest surviving examples were found under the floorboards at Kloster Wienhausen, a convent near Celle in Germany; they have been dated to circa 1400.

Glasses come in many styles. They can be marked or found by their primary function, but also appear in combinations such as prescription sunglasses or safety glasses with enhanced magnification.

Corrective

Corrective lenses are used to correct refractive errors by bending the light entering the eye in order to alleviate the effects of conditions such as nearsightedness (myopia), farsightedness (Hypermetropia) or astigmatism. The ability of one's eyes to accommodate their focus to near and distant focus alters over time. Also, few people have eyes that show exactly equal refractive characteristics; one may need a "stronger", (i.e. more refracting), lens than the other. A common condition in people over forty years old is presbyopia, which is caused by the eye's crystalline lens losing elasticity, progressively reducing the ability of the lens to accommodate (i.e. to focus on objects close to the eye). Corrective lenses, to bring the image back into focus on the retina, are made to conform to the prescription of an ophthalmologist or optometrist. A lensmeter can be used to verify the specifications of an existing pair of glasses. Corrective eyeglasses can significantly improve the life quality of the wearer. Not only do they enhance the wearer's visual experience, but can also reduce problems that result from eye strain, such as headaches or squinting.

Pinhole glasses are a type of corrective glasses that do not use a lens. Pinhole glasses do not actually refract the light or change focal length. Instead, they create a diffraction limited system, which has an increased depth of field, similar to using a small aperture in photography. This form of correction has many limitations that prevent it from gaining popularity in everyday use. Pinhole glasses can be made in a DIY fashion by making small holes in a piece of card which is then held in front of the eyes with a strap or cardboard arms.

The most common type of corrective lens is "single vision", which has a uniform refractive index. For people with presbyopia and hyperopia, bifocal and trifocal glasses provide two or three different refractive indices, respectively, and progressive lenses have a continuous gradient. Reading glasses provide a separate set of glasses for focusing on close-by objects. Reading glasses are available without prescription from drugstores, and offer a cheap, practical solution, though these have two simple lenses of equal power, so will not correct refraction problems like astigmatism or refractive or prismatic variations between the left and right eye. For total correction of the individual's sight, glasses complying to a recent ophthalmic prescription are required. Adjustable-focus eyeglasses might be used to replace bifocals or trifocals, or might be used to produce cheaper single-vision glasses (since they don't have to be custom-manufactured for every person).

Safety glasses are worn to protect the eyes in different situations. They are made with break-proof plastic lenses to protect the eye from flying debris or other matter. Construction workers, factory workers, machinists and lab technicians are often required to wear safety glasses to shield the eyes from flying debris or hazardous splatters such as blood or chemicals. As of 2017, dentists and surgeons in Canada and other countries are required to wear safety glasses to protect against infection from patients' blood or other body fluids. There are also safety glasses for welding, which are styled like wraparound sunglasses, but with much darker lenses, for use in welding where a full sized welding helmet is inconvenient or uncomfortable. These are often called "flash goggles", because they provide protection from welding flash. Nylon frames are usually used for protection eyewear for sports because of their lightweight and flexible properties. Unlike most regular glasses, safety glasses often include protection beside the eyes as well as in front of the eyes.

Sunglasses

Sunglasses provide improved comfort and protection against bright light and often against ultraviolet (UV) light. Photochromic lenses, which are photosensitive, darken when struck by UV light. The dark tint of the lenses in a pair of sunglasses blocks the transmission of light through the lens.

Light polarization is an added feature that can be applied to sunglass lenses. Polarization filters are positioned to remove horizontally polarized rays of light, which eliminates glare from horizontal surfaces (allowing wearers to see into water when reflected light would otherwise overwhelm the scene). Polarized sunglasses may present some difficulties for pilots since reflections from water and other structures often used to gauge altitude may be removed. Liquid crystal displays often emit polarized light making them sometimes difficult to view with polarized sunglasses. Sunglasses may be worn just for aesthetic purposes, or simply to hide the eyes. Examples of sunglasses that were popular for these reasons include teashades and mirrorshades. Many blind people wear nearly opaque glasses to hide their eyes for cosmetic reasons.

Sunglasses may also have corrective lenses, which requires a prescription. Clip-on sunglasses or sunglass clips can be attached to another pair of glasses. Some wrap-around sunglasses are large enough to be worn over top of another pair of glasses. Otherwise, many people opt to wear contact lenses to correct their vision so that standard sunglasses can be used.

The illusion of three dimensions on a two dimensional surface can be created by providing each eye with different visual information. 3D glasses create the illusion of three dimensions by filtering a signal containing information for both eyes. The signal, often light reflected off a movie screen or emitted from an electronic display, is filtered so that each eye receives a slightly different image. The filters only work for the type of signal they were designed for.

Anaglyph 3D glasses have a different colored filter for each eye, typically red and blue or red and green. A polarized 3D system on the other hand uses polarized filters. Polarized 3D glasses allow for color 3D, while the red-blue lenses produce an image with distorted coloration. An active shutter 3D system uses electronic shutters. Head-mounted displays can filter the signal electronically and then transmit light directly into the viewers eyes.

Anaglyph and polarized glasses are distributed to audiences at 3D movies. Polarized and active shutter glasses are used with many home theaters. Head-mounted displays are used by a single person, but the input signal can be shared between multiple units.

Magnification (bioptics)

Glasses can also provide magnification that is useful for people with vision impairments or specific occupational demands. An example would be bioptics or bioptic telescopes which have small telescopes mounted on, in, or behind their regular lenses. Newer designs use smaller lightweight telescopes, which can be embedded into the corrective glass and improve aesthetic appearance (mini telescopic spectacles). They may take the form of self-contained glasses that resemble goggles or binoculars, or may be attached to existing glasses.

Yellow-tinted computer/gaming glasses

Yellow tinted glasses are a type of glasses with a minor yellow tint. They perform minor color correction, on top of reducing headaches due to lack of blinking. They may also be considered minor corrective unprescribed glasses. Depending on the company, these computer or gaming glasses can also filter out high energy blue and ultra-violet light from LCD screens, fluorescent lighting, and other sources of light. This allows for reduced eye-strain. These glasses can be ordered as standard or prescription lenses that fit into standard optical frames. Due to the ultra-violet light blocking nature of these lenses, they also help users sleep at night along with reducing age-related macular degeneration.

Anti-glare protection glasses

Anti-glare protection glasses, or anti-reflective glasses, can reduce the reflection of light that enters our eyes. The lenses are given an anti-glare coating to prevent reflections of light under different lighting conditions. By reducing the amount of glare on your eyes, vision can be improved. The anti-glare also applies to the outer glass, thus allowing for better eye contact.

Related pages

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Eyeglasses (U.S), or spectacles (Brit.) are pieces of glass or clear plastic, called lenses, in a frame that holds them in front of someone's eyes. Corrective lenses let some people see or read better if they have problems seeing. This is used by person who have poor eyesight.

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Clothing is an item or fabric which is made to cover part of the human body. Humans are the only animals which wear clothing, and almost all people do wear clothing.

The torso (body) can be covered by a shirt, arms by sleeves, legs by pants or skirt, the hands by gloves, and feet by footwear. In cold climates, people also wear heavy, thick coats such as trenchcoats.

Clothing protects the human body from the hot sun and high temperatures in warm tropical countries. Clothing such as thick wool coats and boots keeps the human body warm in very cold temperatures (such as in the arctic). To some extent, clothing protects people from damage to their body.

Clothing is also worn for decoration, as a fashion (clothing). People from different cultures wear different clothing, and have different beliefs and customs about what type of clothing should be worn. For many people, clothing is a status symbol. It helps people project an image. Often, clothing is a form of self-expression. Adults in different social or work situations present different views of themselves by the clothes they wear. Young people have an entirely different form of dress to express their personalities. Often people will simply follow popular fashion styles so that they will fit in. Clothing is far more than just a means to protect our bodies.

Origin of clothing

There is no easy way to be sure when clothing was first developed, because it was prehistoric and clothing is perishable. Some information comes from studying lice. The body louse lives in clothing, and diverged from head lice about 107,000 years ago. This suggests that clothing existed at that time. Another theory is that modern humans are the only survivors of several species of primates who may have worn clothes, and that clothing may have been used as long ago as 650 thousand years ago. Other louse-based estimates put the introduction of clothing at around 42,000-72,000 BC.

A cloak made of the fur of squirrels, from a cave in Italy, has been dated to 23.000 years BP, and is possibly among the oldest items of clothing.

Things that are not clothing

People often decorate their bodies with makeup or perfume, and they also cut or change the hair on their heads and faces. They might also go in for body modification: tattoos, scarifications, and body piercings. But makeup and tattoos are not kinds of clothing.

Things that are carried and not worn, like wallets, purses, canes, and umbrellas, are called accessories, but they are not kinds of clothing, either. Jewelry and eyeglasses are also accessories that are put on the body. Nail polish is also put on the fingertips and can be interpreted as makeup.

What clothing is made of

Clothing is often made of:

Needed to make clothing

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Clothing is an item or fabric which is made to cover part of the human body. Humans are the only animals which wear clothing, and almost all people do wear clothing. The torso (body) can be covered by a shirt, arms by sleeves, legs by pants or skirt, the hands by gloves, and feet by footwear.

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A shoe is a type of footwear. It is an item of clothing. Shoes come in pairs, with one shoe for each foot.

There are many different types of shoes. Athletic shoes, for example, are to make running, walking or jogging easier by making the weight of the shoe lighter and the sole of the shoe softer. Leather shoes are formal shoes. There are worn for business and ceremonial functions. They are also worn for fashion. Slippers are a kind of indoor shoe. They are often worn when it is cold. Rubber boots are used on rainy days. The shoes with a high heel which women wear are called high heels.

People usually wear shoes in public. They are worn for hygiene, style, and comfort.

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Dutch pattens, ca. 1465. Excavated from the archeological site of Walraversijde, near Ostend, Belgium

A shoemaker in the Georgian era, from The Book of English Trades, 1821.

Advertisement in an 1896 issue of McClure's for "The Regal".

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A shoe is a type of footwear. It is an item of clothing. Shoes come in pairs, with one shoe for each foot. There are many different types of shoes. Athletic shoes, for example, are to make running, walking or jogging easier by making the weight of the shoe lighter and the sole of the shoe softer.

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Space exploration is a term which describes searching outer space. There are many reasons for space exploration. The most important reasons are scientific research and the interest of humans to learn more about outer space. For centuries, humans had dreamt of reaching outer space. Better rockets made it possible in the 20th century. On October 4, 1957, the former Soviet Union launched the Sputnik I, which was the first artificial satellite. This started the Space Race and people later went into orbit and Americans visited the Moon in Project Apollo. Many space probes have gone to the various planets and other places in the solar system to send back information about them.

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Space exploration is a term which describes searching outer space. There are many reasons for space exploration. The most important reasons are scientific research and the interest of humans to learn more about outer space. For centuries, humans had dreamt of reaching outer space. Better rockets made it possible in the 20th century.

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Education is about teaching and learning skills and knowledge. Education also means helping people to learn how to do things and encouraging them to think about what they learn. It is also important for educators to teach ways to find and use information.

Through education, the knowledge of society, country, and of the world is passed on from generation to generation. In democracies, through education, children and adults are supposed to learn how to be active and effective citizens.

More specific, education helps and guide individuals to transform from one class to other. Empowered individuals, societies, countries by education are taking edge over individuals stand on bottom pyramid of growth.

There are different methods of categorizing types of education. One way is to divide it into formal education, non-formal education, and informal education.

Formal education is usually in school, where a person may learn basic, academic, or trade skills. Small children often attend a nursery or kindergarten but often formal education begins in elementary school and continues with secondary school. Post-secondary education (or higher education) is usually at a college or university which may grant an academic degree.

Non-formal education includes adult basic education, adult literacy education or school equivalency preparation. In nonformal education someone (who is not in school) can learn literacy, other basic skills or job skills. Home education, individualized instruction (such as programmed learning), distance learning and computer-assisted instruction are other possibilities.

Informal education may be a parent teaching a child how to prepare a meal or ride a bicycle. People can also get an informal education by reading many books from a library or educational websites. Informal education is when you are not studying in a school and do not use any particular learning method.

Many public schools provide a free education through the government. Parents may send their children to a private schools, but they must pay for it. In some poorer places, some children cannot go to school, because their countries do not make education available in their countries, or because their families do not have enough money, or because the children have to work for money, or because the society have negative prejudice on education for girls.

There are primary schools and secondary schools. In many places they are government funded. Colleges and universities usually charge Tuition payments which may be very different in different countries.

Education began in prehistory, as adults trained the young in the knowledge and skills deemed necessary in their society. In pre- literate societies, this was achieved orally and through imitation. Story-telling passed knowledge, values, and skills from one generation to the next. As cultures began to extend their knowledge beyond skills that could be readily learned through imitation, formal education developed. Schools existed in Egypt at the time of the Middle Kingdom.

Plato founded the Academy in Athens, the first institution of higher learning in Europe. The city of Alexandria in Egypt, established in 330 BCE, became the successor to Athens as the intellectual cradle of Ancient Greece. There, the great Library of Alexandria was built in the 3rd century BCE. European civilizations suffered a collapse of literacy and organization following the fall of Rome in CE 476.

In China, Confucius (551-479 BCE), of the State of Lu, was the country's most influential ancient philosopher, whose educational outlook continues to influence the societies of China and neighbours like Korea, Japan, and Vietnam. Confucius gathered disciples and searched in vain for a ruler who would adopt his ideals for good governance, but his Analects were written down by followers and have continued to influence education in East Asia into the modern era.

After the Fall of Rome, the Catholic Church became the sole preserver of literate scholarship in Western Europe. The church established cathedral schools in the Early Middle Ages as centres of advanced education. Some of these establishments ultimately evolved into medieval universities and forebears of many of Europe's modern universities. During the High Middle Ages, Chartres Cathedral operated the famous and influential Chartres Cathedral School. The medieval universities of Western Christendom were well-integrated across all of Western Europe, encouraged freedom of inquiry, and produced a great variety of fine scholars and natural philosophers, including Thomas Aquinas of the University of Naples, Robert Grosseteste of the University of Oxford, an early expositor of a systematic method of scientific experimentation, and Saint Albert the Great, a pioneer of biological field research. Founded in 1088, the University of Bologne is considered the first, and the oldest continually operating university.

Elsewhere during the Middle Ages, Islamic science and mathematics flourished under the Islamic caliphate which was established across the Middle East, extending from the Iberian Peninsula in the west to the Indus in the east and to the Almoravid Dynasty and Mali Empire in the south.

The Renaissance in Europe ushered in a new age of scientific and intellectual inquiry and appreciation of ancient Greek and Roman civilizations. Around 1450, Johannes Gutenberg developed a printing press, which allowed works of literature to spread more quickly. The European Age of Empires saw European ideas of education in philosophy, religion, arts and sciences spread out across the globe. Missionaries and scholars also brought back new ideas from other civilizations - as with the Jesuit China missions who played a significant role in the transmission of knowledge, science, and culture between China and Europe, translating works from Europe like Euclid's Elements for Chinese scholars and the thoughts of Confucius for European audiences. The Enlightenment saw the emergence of a more secular educational outlook in Europe.

In most countries today, full-time education, whether at school or otherwise, is compulsory for all children up to a certain age. Due to this the proliferation of compulsory education, combined with population growth, UNESCO has calculated that in the next 30 years more people will receive formal education than in all of human history thus far.

Formal education

Formal education occurs in a structured environment whose explicit purpose is teaching students. Usually, formal education takes place in a school environment with classrooms of multiple students learning together with a trained, certified teacher of the subject. Most school systems are designed around a set of values or ideals that govern all educational choices in that system. Such choices include curriculum, organizational models, design of the physical learning spaces (e.g. classrooms), student-teacher interactions, methods of assessment, class size, educational activities, and more.

Preschools provide education from ages approximately three to seven, depending on the country when children enter primary education. These are also known as nursery schools and as kindergarten, except in the US, where kindergarten is a term used for primary education. Kindergarten "provide[s] a child-centred, preschool curriculum for three- to seven-year-old children that aim[s] at unfolding the child's physical, intellectual, and moral nature with balanced emphasis on each of them."

Primary (or elementary) education consists of the first five to seven years of formal, structured education. In general, primary education consists of six to eight years of schooling starting at the age of five or six, although this varies between, and sometimes within, countries. Globally, around 89% of children aged six to twelve are enrolled in primary education, and this proportion is rising. Under the Education For All programs driven by UNESCO, most countries have committed to achieving universal enrollment in primary education by 2015, and in many countries, it is compulsory. The division between primary and secondary education is somewhat arbitrary, but it generally occurs at about eleven or twelve years of age. Some education systems have separate middle schools, with the transition to the final stage of secondary education taking place at around the age of fourteen. Schools that provide primary education, are mostly referred to as primary schools or elementary schools. Primary schools are often subdivided into infant schools and junior school.

In India, for example, compulsory education spans over twelve years, with eight years of elementary education, five years of primary schooling and three years of upper primary schooling. Various states in the republic of India provide 12 years of compulsory school education based on a national curriculum framework designed by the National Council of Educational Research and Training.

In most contemporary educational systems of the world, secondary education comprises the formal education that occurs during adolescence. It is characterized by transition from the typically compulsory, comprehensive primary education for minors, to the optional, selective tertiary, "postsecondary", or " higher" education (e.g. university, vocational school) for adults. Depending on the system, schools for this period, or a part of it, may be called secondary or high schools, gymnasiums, lyceums, middle schools, colleges, or vocational schools. The exact meaning of any of these terms varies from one system to another. The exact boundary between primary and secondary education also varies from country to country and even within them but is generally around the seventh to the tenth year of schooling. Secondary education occurs mainly during the teenage years. In the United States, Canada, and Australia, primary and secondary education together are sometimes referred to as K-12 education, and in New Zealand Year 1-13 is used. The purpose of secondary education can be to give common knowledge, to prepare for higher education, or to train directly in a profession.

Secondary education in the United States did not emerge until 1910, with the rise of large corporations and advancing technology in factories, which required skilled workers. In order to meet this new job demand, high schools were created, with a curriculum focused on practical job skills that would better prepare students for white collar or skilled blue collar work. This proved beneficial for both employers and employees, since the improved human capital lowered costs for the employer, while skilled employees received higher wages.

Secondary education has a longer history in Europe, where grammar schools or academies date from as early as the 16th century, in the form of public schools, fee-paying schools, or charitable educational foundations, which themselves date even further back.

Community colleges offer another option at this transitional stage of education. They provide nonresidential junior college courses to people living in a particular area.

Tertiary (higher)

Higher education, also called tertiary, third stage, or postsecondary education, is the non-compulsory educational level that follows the completion of a school such as a high school or secondary school. Tertiary education is normally taken to include undergraduate and postgraduate education, as well as vocational education and training. Colleges and universities mainly provide tertiary education. Collectively, these are sometimes known as tertiary institutions. Individuals who complete tertiary education generally receive certificates, diplomas, or academic degrees.

Higher education typically involves work towards a degree-level or foundation degree qualification. In most developed countries, a high proportion of the population (up to 50%) now enter higher education at some time in their lives. Higher education is therefore very important to national economies, both as a significant industry in its own right and as a source of trained and educated personnel for the rest of the economy.

University education includes teaching, research, and social services activities, and it includes both the undergraduate level (sometimes referred to as tertiary education) and the graduate (or postgraduate) level (sometimes referred to as graduate school). Universities are generally composed of several colleges. In the United States, universities can be private and independent like Yale University; public and state-governed like the Pennsylvania State System of Higher Education; or independent but state-funded like the University of Virginia. A number of career specific courses are now available to students through the Internet.

One type of university education is a liberal arts education, which can be defined as a " college or university curriculum aimed at imparting broad general knowledge and developing general intellectual capacities, in contrast to a professional, vocational, or technical curriculum." Although what is known today as liberal arts education began in Europe, the term " liberal arts college" is more commonly associated with institutions in the United States.

Vocational

Vocational education is a form of education focused on direct and practical training for a specific trade or craft. Vocational education may come in the form of an apprenticeship or internship as well as institutions teaching courses such as carpentry, agriculture, engineering, medicine, architecture and the arts.

In the past, those who were disabled were often not eligible for public education. Children with disabilities were repeatedly denied an education by physicians or special tutors. These early physicians (people like Itard, Seguin, Howe, Gallaudet) set the foundation for special education today. They focused on individualized instruction and functional skills. In its early years, special education was only provided to people with severe disabilities, but more recently it has been opened to anyone who has experienced difficulty learning.

Other educational forms

Alternative

While considered "alternative" today, most alternative systems have existed since ancient times. After the public school system was widely developed beginning in the 19th century, some parents found reasons to be discontented with the new system. Alternative education developed in part as a reaction to perceived limitations and failings of traditional education. A broad range of educational approaches emerged, including alternative schools, self learning, homeschooling, and unschooling. Example alternative schools include Montessori schools, Waldorf schools (or Steiner schools), Friends schools, Sands School, Summerhill School, Walden's Path, The Peepal Grove School, Sudbury Valley School, Krishnamurti schools, and open classroom schools. Charter schools are another example of alternative education, which have in the recent years grown in numbers in the US and gained greater importance in its public education system.

In time, some ideas from these experiments and paradigm challenges may be adopted as the norm in education, just as Friedrich Fröbel's approach to early childhood education in 19th-century Germany has been incorporated into contemporary kindergarten classrooms. Other influential writers and thinkers have included the Swiss humanitarian Johann Heinrich Pestalozzi; the American transcendentalists Amos Bronson Alcott, Ralph Waldo Emerson, and Henry David Thoreau; the founders of progressive education, John Dewey and Francis Parker; and educational pioneers such as Maria Montessori and Rudolf Steiner, and more recently John Caldwell Holt, Paul Goodman, Frederick Mayer, George Dennison, and Ivan Illich.

Indigenous

Indigenous education refers to the inclusion of indigenous knowledge, models, methods, and content within formal and non-formal educational systems. Often in a post-colonial context, the growing recognition and use of indigenous education methods can be a response to the erosion and loss of indigenous knowledge and language through the processes of colonialism. Furthermore, it can enable indigenous communities to "reclaim and revalue their languages and cultures, and in so doing, improve the educational success of indigenous students."

Informal learning

Informal learning is one of three forms of learning defined by the Organisation for Economic Co-operation and Development (OECD). Informal learning occurs in a variety of places, such as at home, work, and through daily interactions and shared relationships among members of society. For many learners, this includes language acquisition, cultural norms, and manners. Informal learning for young people is an ongoing process that also occurs in a variety of places, such as out of school time, in youth programs at community centres and media labs.

Informal learning usually takes place outside educational establishments, does not follow a specified curriculum and may originate accidentally, sporadically, in association with certain occasions, from changing practical requirements. It is not necessarily planned to be pedagogically conscious, systematic and according to subjects, but rather unconsciously incidental, holistically problem-related, and related to situation management and fitness for life. It is experienced directly in its " natural" function of everyday life and is often spontaneous.

The concept of 'education through recreation' was applied to childhood development in the 19th century. In the early 20th century, the concept was broadened to include young adults but the emphasis was on physical activities. L.P. Jacks, also an early proponent of lifelong learning, described education through recreation: "A master in the art of living draws no sharp distinction between his work and his play, his labour and his leisure, his mind and his body, his education and his recreation. He hardly knows which is which. He simply pursues his vision of excellence through whatever he is doing and leaves others to determine whether he is working or playing. To himself, he always seems to be doing both. Enough for him that he does it well." Education through recreation is the opportunity to learn in a seamless fashion through all of life's activities. The concept has been revived by the University of Western Ontario to teach anatomy to medical students.

Open education and electronic technology

In 2012, the modern use of electronic educational technology (also called e-learning) had grown at 14 times the rate of traditional learning. Open education is fast growing to become the dominant form of education, for many reasons such as its efficiency and results compared to traditional methods. Cost of education has been an issue throughout history, and a major political issue in most countries today. Online courses often can be more expensive than face-to-face classes. Out of 182 colleges surveyed in 2009 nearly half said tuition for online courses was higher than for campus-based ones. Many large university institutions are now starting to offer free or almost free full courses such as Harvard, MIT and Berkeley teaming up to form edX. Other universities offering open education are Stanford, Princeton, Duke, Johns Hopkins, Edinburgh, U. Penn, U. Michigan, U. Virginia, U. Washington, and Caltech. It has been called the biggest change in the way we learn since the printing press. Despite favourable studies on effectiveness, many people may still desire to choose traditional campus education for social and cultural reasons.

The conventional merit-system degree is currently not as common in open education as it is in campus universities, although some open universities do already offer conventional degrees such as the Open University in the United Kingdom. Presently, many of the major open education sources offer their own form of certificate. Due to the popularity of open education, these new kind of academic certificates are gaining more respect and equal "academic value" to traditional degrees. Many open universities are working to have the ability to offer students standardized testing and traditional degrees and credentials.

A culture is beginning to form around distance learning for people who are looking to social connections enjoyed on traditional campuses. For example, students may create study groups, meetups, and movements such as UnCollege.

Economics of education

It has been argued that high rates of education are essential for countries to be able to achieve high levels of economic growth. Empirical analyses tend to support the theoretical prediction that poor countries should grow faster than rich countries because they can adopt cutting edge technologies already tried and tested by rich countries. However, technology transfer requires knowledgeable managers and engineers who are able to operate new machines or production practices borrowed from the leader in order to close the gap through imitation. Therefore, a country's ability to learn from the leader is a function of its stock of "human capital". Recent study of the determinants of aggregate economic growth have stressed the importance of fundamental economic institutions and the role of cognitive skills.

At the level of the individual, there is a large literature, generally related to the work of Jacob Mincer, on how earnings are related to the schooling and other human capital. This work has motivated a large number of studies, but is also controversial. The chief controversies revolve around how to interpret the impact of schooling. Some students who have indicated a high potential for learning, by testing with a high intelligence quotient, may not achieve their full academic potential, due to financial difficulties.

Economists Samuel Bowles and Herbert Gintis argued in 1976 that there was a fundamental conflict in American schooling between the egalitarian goal of democratic participation and the inequalities implied by the continued profitability of capitalist production.

The future of education

Many countries are now drastically changing the way they educate their citizens. The world is changing at an ever quickening rate, which means that a lot of knowledge becomes obsolete and inaccurate more quickly. The emphasis is therefore shifting to teaching the skills of learning: to picking up new knowledge quickly and in as agile a way as possible. Finnish schools have even begun to move away from the regular subject-focused curricula, introducing instead developments like phenomenon-based learning, where students study concepts like climate change instead.

Education is also becoming a commodity no longer reserved for children. Adults need it too. Some governmental bodies, like the Finnish Innovation Fund Sitra in Finland, have even proposed compulsory life-long education.

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Education is about teaching and learning skills and knowledge. Education also means helping people to learn how to do things and encouraging them to think about what they learn. It is also important for educators to teach ways to find and use information.

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An important difference between pens and pencils is that the tip of a pencil is made of graphite (or lead) and pens have tips made of metal with ink coming out of the bottom. Pencil writings do not smudge or wash away if the paper gets wet, unlike pens which have ink.

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School colors are the colors representing the school of which one goes to.

School colors are often found in pairs and rarely no more than trios, though some professional teams use up to four colors in a set. The choice of colors usually follows the rule of tincture from heraldry, but exceptions to this rule are known.

Common primary colors include , , , , and . These colors are either paired with a color representing a metal (often , , (or ), , or ), or occasionally each other, such as orange/blue, red/green, or blue/yellow. Pairing two metals, such as black/white, silver or gold, and especially black/gold, is also a common practice. Finally, some American schools, in a display of patriotism, adopt the national colors of red/white/blue.

In an effort to further establish identity and promote a standard, many institutions often decree the use of specific shades of colors. generally regarded as a darker shade of red, is a common primary color. Various shades of blue, from powder to Prussian, are also in use; a few schools have adopted two different shades of blue for their colors, with the darker shade serving as the primary. The shade of gold can vary greatly even within an institution, from a vivid yellow to a more convincing old gold.

Black, white and gray are often used as neutral colors for sets that do not otherwise adopt them. This practice is especially notable in basketball (where home uniforms are often white) and professional baseball (where team colors are often used as trim for white or gray uniforms).

Most competitive teams keep two sets of uniforms, with one design emphasizing the primary color and the other emphasizing the secondary color. In some sports, such as football, the primary color is emphasized on home uniforms, while uniforms for other sports, notably basketball, use the secondary or a neutral color at home. This is done to avoid confusion when playing a team with similar colors.

In addition, various groups that generate support for athletic teams, including cheerleaders and marching bands, wear uniforms with the colors of their school.

At many private schools 'school colours' are awards presented for achievement in a subject or a sport - See Sporting Colours.

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School colors are the colors representing the school of which one goes to. School colors are often found in pairs and rarely no more than trios, though some professional teams use up to four colors in a set. The choice of colors usually follows the rule of tincture from heraldry, but exceptions to this rule are known.

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A sport is commonly defined as an athletic activity or skill and involves a degree of competition, such as baseball, soccer, bowling, or basketball. Many people play sports with their friends. Sportsmen need coaches to teach or train teams or individuals how to do better. Sports can be played indoors or outdoors and by individuals or teams.

Some people like to watch other people play sports. Those who watch others playing sports are called . While some fans watch sports on television, others actually go to stadiums or other places where people pay to watch them in person. These fans are called spectators.

People engage in many kinds of sports, for example:

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Electronic sports are a recent development.

Spectators at the 1906 unofficial Olympic Games

Modern sports have complex rules and are highly organized.

A runner gives a friendly tap on the shoulder to a wheelchair racer during the Marathon International de Paris (Paris Marathon) in 2014.

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A sport is commonly defined as an athletic activity or skill and involves a degree of competition, such as baseball, soccer, bowling, or basketball. Many people play sports with their friends. Sportsmen need coaches to teach or train teams or individuals how to do better.

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A toy is something to play with. Toys are for children, adults, and animals. Before 1970, most toys were made of metal and wood. Now, they are mostly made of plastic. Sometimes they are made of electronic material. Some people also consider video games toys. Toys include balls, plastic cars, and dolls.

Toys originated many years ago. Dolls of infants, animals, and soldiers and toy tools are found in archaeological places. The origin of the word "toy" is not known. However, it is thought that it was first used in the 14th century.

The earliest toys were made from rocks, sticks or clay. In Ancient Egypt, children played with dolls made of clay and sticks. In Ancient Greece and Ancient Rome, children played with dolls made of wax or terracotta, sticks, bows and arrows, and yo-yos. When Greek children, especially girls became adults, it was required to sacrifice the toys to the gods. On the eve of their wedding, young girls around fourteen would offer their dolls in a temple as a rite of passage into adulthood.

Images for kids

Little horse on wheels, Ancient Greek child's toy. From a tomb dating 950-900 BCE, Kerameikos Archaeological Museum, Athens

Frank Hornby's 1901 patent number GB190100587A for what later became known as Meccano

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A toy is something to play with. Toys are for children, adults, and animals. Before 1970, most toys were made of metal and wood. Now, they are mostly made of plastic. Sometimes they are made of electronic material. Some people also consider video games toys. Toys include balls, plastic cars, and dolls.

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Video games are electronic games played on a video screen (normally a television, a built-in screen when played on a handheld machine, or a computer).

There are many types, or genres, of these games: role-playing games; shooters, first-person shooters, side-scrollers, and platformers are just a few.

Video games usually come on CDs, DVDs or digital download. Many games used to come on cartridges. A specialised device used to play a video game at home is called a console. There have been many types of consoles and home computers used to play video games. Some of the first were the Atari 2600, the Sega Master System and Nintendo Entertainment System in the 1980s. Newer video game consoles are the Xbox One, PlayStation 4, and Wii U. The best selling video game console of all time is the PlayStation 2, made by Sony.

People can also use PCs to play games, which are sometimes called PC games. The older consoles do not have new games developed for them often, although console games are emulated for PCs (see emulator). This means that new computers can play many old console games along with games made just for new computers. Older games are often more popular emulated than when they were first on sale, because of the ease of download.

People can play portable video games anywhere. Mobile devices (running operating systems such as iOS or Android) also can download games, making them portable game machines. Mobile phones have many games, some of them using a mobile emulator for games from consoles.

Competitions of video game players are called electronic sports.

Current generation consoles

Microsoft's Xbox One came out in November 2013. It is the new version of the Xbox and Xbox 360. It offers a similar online experience and controller to its predecessor, but with improved graphics. Like the original and 360 versions, it also allows people to put music from an MP3 player or other sources onto the system. It was the last 8th generation console to come out.

Sony's PlayStation 4 (PS4) came out in November 2013. It is the newest of the PlayStation game consoles. It also has better graphics and online gameplay. Like the PSP and PS3, the PS4 can play movies, music, and browse the internet.

Nintendo released the Wii U in November 2012. It is the first console from Nintendo with high-definition graphics. Like the Wii, it has a unique controller. Its controller is shaped like a tablet computer with ordinary controller buttons around the edges of the screen.

Current hand held consoles

Sony's PlayStation Portable (PSP) came out in 2004. Along with Nintendo's Dual Screen (DS) in 2004, and now the new Nintendo DSi XL, which is an advancement from their original Nintendo DSi. Nintendo also released the 3DS, which is the first handheld 3D console, the 2DS and now the New 3DS XL, which is similar to the 3DS but with updated graphical capabilities.. PlayStation Vita has had its first release in Japan on November 18, 2012 and in the North-America on February 4, 2013.

History of video games

The first video game ever is often said to be a computer game called Spacewar!. In fact, some ideas of video games can be found before people made Spacewar!.

In the 1950s, when the first computers began to be made, three people had some ideas to create the basis of actual video games. In 1951, Ralph Baer, an American engineer of Loral Electronics, tried to create "the best television", proposing to add a gaming module, but his employer did not like his idea. Even if his idea was never realized, he is the first man to have thought of the idea of video games, later creating the first video game console, the Odyssey. Later, in 1952, A.S Douglas, of the Cambridge University in the UK, made a video game on a computer in order to illustrate one of his speeches. The game, called OXO, was a tic-tac-toe game, with two players (the person itself and the opponent, the computer) .In 1953, Willy Higinbotham made a game called Tennis For Two, similar to the later , to entertain visitors to Brookhaven National Laboratory.

One of the most famous and one of the earliest video games ever is called Space Invaders. Space Invaders was made in 1978 as a coin operated arcade game but a version has been made for almost every game console and home computer ever available.

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la:Ludus computatralis

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Video games are electronic games played on a video screen (normally a television, a built-in screen when played on a handheld machine, or a computer). There are many types, or genres, of these games: role-playing games; shooters, first-person shooters, side-scrollers, and platformers are just a few.

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A book is a set of printed sheets of paper held together between two covers. The sheets of paper are usually covered with a text, language and illustrations that is the main point of a printed book.

A writer of a book is called an author. Someone who draws pictures in a book is called an illustrator. Books can have multiple authors or illustrators.

A book can also be a text in a larger collection of texts. That way a book is perhaps written by one author, or it only treats one subject area. Books in this sense can often be understood without knowing the whole collection. Examples are the Bible, the Illiad or the Odyssey - all of them consist of a number of books in this sense of the word. Encyclopedias often have separate articles written by different people, and published as separate volumes. Each volume is a book.

Hardcover books have hard covers made of cardboard covered in cloth or leather and are usually sewn together. Paperback books have covers of stiff paper and are usually glued together. The words in books may be read aloud or recorded on tapes (audiobooks) and compact discs.

Books can be borrowed from a library or bought from a bookstore. People can make their own books and fill them with family photos, drawings, or their own writing. Some books are empty inside, like a diary, address book, or photo album. Most of the time, the word "book" means that the pages inside have words printed or written on them.

Some books are written just for children, or for entertainment, while other books are for studying something in school such as math or history. Many books have photographs or drawings.

People who cannot read books, or any type of writing are called illiterate (= 'unlettered').

Types of books

There are two main kinds of book text: fiction and non-fiction.

These books are novels, about stories that did not happen, and have been imagined by the author. Some books are based on real events from history, but the author has created imaginary characters or dialogue for the events.

Non-fiction

Books of non-fiction are about true facts or things that have really happened. Some examples are dictionaries, cookbooks, textbooks for learning in school, or a biography (someone's life story).

Historical

Between the written manuscript and the book lie several inventions. A book is an industrial product, but manuscripts are hand-made.

Manuscripts

A common type of manuscript was the scroll, which was a long sheet rolled up. The sheet could have been made of papyrus (made by the Egyptians, by weaving the inner stems of the papyrus plant and then hammering them together), or parchment or vellum (very thin animal skin, first used by the ancient Greeks), or paper (made from plant fibers, invented by the Chinese). Turning the manuscript into a book required several developments.

The Romans were the first people to put separate pieces of manuscript between covers, to form a codex. This was more convenient to handle and store than scrolls, but was not yet a book as we understand it.

Scrolls and codices were written and copied by hand. The Chinese invented woodblock printing, where shapes are carved out of a block of wood, then ink is applied to the carved side, and the block is pressed onto the paper. This way of making books was very slow, and so very few people had these kinds of books.

Johannes Gutenberg was the first to invent a machine for printing, the printing press, in the 15th century. This involved more than just a press, it involved the production of movable metal type suitable for the machine process.

Initially, the machines were slow, and needed a printer to work with them. Fast and automatic machines did not arrive until the 19th century.

Paper and ink

Paper had been invented in the 8th century, but hand-made paper was expensive and in short supply. In the 19th century, automated or semi-automated making of paper from wood pulp was invented. Also, there was the invention of inks for various purposes, and machines driven by electricity.

The common cheap supply of paper fed the faster printing machines, and books became cheaper. Only then could ordinary people afford to buy books. Along with these inventions in the 19th century came the idea of public libraries, so poorer people could get access to the best books. Also, widespread free (or nearly free) education swelled the number of literate people.

Printing was done on large sheets of paper, which were then folded, guillotined (cut) and sewn in sections, and finally placed into the covers. All these processes became done by machines during the 19th century.

Today some of the technologies have been changed, especially those involving illustration and typography. However, books look much the same as they did, with more illustration in colour, but basically the same. That is because experience has shown that readers need certain things for pleasurable reading. Graphic design and typography are the practical arts used to make books attractive and useful to readers.

Digital printing

Recent developments in book manufacturing include the development of digital printing. Book pages are printed, in much the same way as an office copier works, using toner rather than ink. Each book is printed in one pass, not as separate signatures. Digital printing has permitted the manufacture of much smaller quantities than offset, in part because of the absence of make readies and of spoilage. One might think of a web press as printing quantities over 2000, quantities from 250 to 2000 being printed on sheet-fed presses, and digital presses doing quantities below 250. These numbers are of course only approximate and will vary from supplier to supplier, and from book to book depending on its characteristics. Digital printing has opened up the possibility of print-on-demand, where no books are printed until after an order is received from a customer.

In the 2000s, due to the rise in availability of affordable handheld computing devices, the opportunity to share texts through electronic means became a more appealing option for media publishers. Thus, the "e-book" was made. The term e-book is a contraction of "electronic book"; it refers to a book-length publication in digital form. An e-book is usually made available through the internet, but also on CD-ROM and other forms. E-Books may be read either via a computer or by means of a portable book display device known as an e-book reader, such as the Sony Reader, Barnes & Noble Nook, Kobo eReader, or the Amazon Kindle. These devices attempt to mimic the experience of reading a print book.

Paper and conservation

Paper was first made in China as early as 200 BC, and reached Europe through Muslim territories. At first made of rags, the industrial revolution changed paper-making practices, allowing for paper to be made out of wood pulp. Papermaking in Europe began in the 11th century, although vellum was also common there as page material up until the beginning of the 16th century, vellum being the more expensive and durable option. Printers or publishers would often issue the same publication on both materials, to cater to more than one market.

Paper made from wood pulp became popular in the early 20th century, because it was cheaper than linen or abaca cloth-based papers. Pulp-based paper made books less expensive to the general public. This paved the way for huge leaps in the rate of literacy in industrialised nations, and enabled the spread of information during the Second Industrial Revolution.

Pulp paper, however, contains acid which eventually destroys the paper from within. Earlier techniques for making paper used limestone rollers, which neutralized the acid in the pulp. Books printed between 1850 and 1950 are primarily at risk; more recent books are often printed on acid-free or alkaline paper. Libraries today have to consider mass deacidification of their older collections in order to prevent decay.

Stability of the climate is critical to the long-term preservation of paper and book material. Good air circulation is important to keep fluctuation in climate stable. The HVAC system should be up to date and functioning efficiently. Light is detrimental to collections. Therefore, care should be given to the collections by implementing light control. General housekeeping issues can be addressed, including pest control. In addition to these helpful solutions, a library must also make an effort to be prepared if a disaster occurs, one that they cannot control. Time and effort should be given to create a concise and effective disaster plan to counteract any damage incurred through "acts of God" therefore an emergency management plan should be in place.

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Folio 14 recto of the 5th century Vergilius Romanus contains an author portrait of Virgil. Note the bookcase ( capsa), reading stand and the text written without word spacing in rustic capitals.

Burgundian author and scribe Jean Miélot, from his Miracles de Notre Dame, 15th century.

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A book is a set of printed sheets of paper held together between two covers. The sheets of paper are usually covered with a text, language and illustrations that is the main point of a printed book. A writer of a book is called an author.

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Navigation is how ships or aircraft find their way from one place to another. The word navigation came from the word " navgatih" from the Sanskrit language. The Latin word navis means ship; navigation is literally "art of ship mastery". The word is also used as a metaphor for 'finding one's way'.

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Mail is part of the postal system. The postal system is a system where written documents and small to medium packages are sent (delivered) to places around the world. Anything sent through the postal system is called mail or post.

A postal service can be private or public. Governments often make rules about private postal delivery systems. Since the early 19th century, national postal systems have mostly been controlled entirely by governments. The governments make people pay a fee to send something. This fee is usually in the form of stamps. Some governments only let private postal services deliver parcel (non-mail) packages.

Postal systems often do things other than sending letters. In some countries, the postal system is also in charge of telephone and telegraph systems. The postal systems in other countries can help people apply for government papers such as passports and driver's licenses. Many places the post offices also work like banks. This is so that people can take out money or pay bills at a nearby post office, instead of travelling to a big bank in the nearest town.

Types of mail

Letter-sized mail constitutes the bulk of the contents sent through most postal services. These are usually documents printed on A4 (210×297 mm), Letter-sized (8.5×11 inches), or smaller paper and placed in envelopes.

Handwritten correspondence, while once a major means of communications between distant people, is now used less frequently due to the advent of more immediate means of communication, such as the telephone or e-mail. Traditional letters, however, are often considered to harken back to a "simpler time" and are still used when someone wishes to be deliberate and thoughtful about his or her communication. An example would be a letter of sympathy to a bereaved person.

Bills and invoices are often sent through the mail, like regular billing correspondence from utility companies and other service providers. These letters often contain a self-addressed envelope that allows the receiver to remit payment back to the company easily. While still very common, many people now opt to use online bill payment services, which eliminate the need to receive bills through the mail. Paperwork for the confirmation of large financial transactions is often sent through the mail. Many tax documents are as well.

New credit cards and their corresponding personal identification numbers are sent to their owners through the mail. The card and number are usually mailed separately several days or weeks apart for security reasons.

Bulk mail is mail that is prepared for bulk mailing, often by presorting, and processing at reduced rates. It is often used in direct marketing and other advertising mail, although it has other uses as well. The senders of these messages sometimes purchase lists of addresses (which are sometimes targeted towards certain demographics) and then send letters advertising their product or service to all recipients. Other times, commercial solicitations are sent by local companies advertising local products, like a restaurant delivery service advertising to their delivery area or a retail store sending their weekly advertising circular to a general area. Bulk mail is also often sent to companies' existing subscriber bases, advertising new products or services.

First-Class

First-Class Mail in the U.S. includes postcards, letters, large envelopes (flats), and small packages, providing each piece weighs 13 ounces or less. Delivery is given priority over second-class ( newspapers and magazines), third class (bulk advertisements), and fourth-class mail (books and media packages). First-Class Mail prices are based on both the shape and weight of the item being mailed. Pieces over 13 ounces can be sent as Priority Mail. As of 2011 42% of First-Class Mail arrived the next day, 27% in two days, and 31% in three. The USPS expected that changes to the service in 2012 would cause about 51% to arrive in two days and most of the rest in three.

The British Royal Mail equivalent to USPS First-Class Mail is stylized as 1st Class, and is simply a priority option over 2nd Class, at a slightly higher cost. Royal Mail aims (but does not guarantee) to deliver all 1st Class letters the day after postage.

The Canada Post counterpart is Lettermail.

Registered and recorded mail

Registered mail allows the location and in particular the correct delivery of a letter to be tracked. It is usually considerably more expensive than regular mail, and is typically used for valuable items. Registered mail is constantly tracked through the system.

Recorded mail is handled just like ordinary mail with the exception that it has to be signed for on receipt. This is useful for legal documents where proof of delivery is required.

In the United Kingdom recorded delivery mail (branded as signed for by the Royal Mail) is covered by The Recorded Delivery Services Act 1962. Under this legislation any document which its relevant law requires service by registered post can also be lawfully served by recorded delivery. This act states that any recorded delivery item is deemed to have been delivered at the instant it is posted if; (a) the item is delivered and signed for at the delivery address or handed over and signed for the at local sorting office (see (c)); (b) delivery is refused by any person occupying the address or (c) if the item is not collected from the sorting office within seven days following a non delivery because there is no reply to the postman and he leaves a collection card. The sorting office will return the item to the sender after the seventh day. The sender should retain the item unopened as proof that the item has been delivered (at least in law if not in fact). Although much case law has attempted to undermine the provisions of the Act, it has done little but reinforce the point.

Repositionable notes

The United States Postal Service introduced a test allowing "repositionable notes" (for example, 3M's Post-it notes) to be attached to the outside of envelopes and bulk mailings, afterwards extending the test for an unspecified period.

Postal cards and postcards

Postal cards and postcards are small message cards which are sent by mail unenveloped; the distinction often, though not invariably and reliably, drawn between them is that "postal cards" are issued by the postal authority or entity with the "postal indicia" (or "stamp") preprinted on them, while postcards are privately issued and require affixing an adhesive stamp (though there have been some cases of a postal authority's issuing non-stamped postcards). Postcards are often printed to promote tourism, with pictures of resorts, tourist attractions or humorous messages on the front and allowing for a short message from the sender to be written on the back. The postage required for postcards is generally less than postage required for standard letters; however, certain technicalities such as their being oversized or having cut-outs, may result in payment of the first-class rate being required.

Postcards are also used by magazines for new subscriptions. Inside many magazines are postage-paid subscription cards that a reader can fill out and mail back to the publishing company to be billed for a subscription to the magazine. In this fashion, magazines also use postcards for other purposes, including reader surveys, contests or information requests.

Postcards are sometimes sent by charities to their members with a message to be signed and sent to a politician (e.g. to promote fair trade or third world debt cancellation).

Other mail services

Larger envelopes are also sent through the mail. These are often composed of a stronger material than standard envelopes and are often used by businesses to transport documents that may not be folded or damaged, such as legal documents and contracts. Due to their size, larger envelopes are sometimes charged additional postage.

Packages are often sent through some postal services, usually requiring additional postage than an average letter or postcard. Many postal services have limitations as to what a package may or may not contain, usually placing limits or bans on perishable, hazardous or flammable materials. Some hazardous materials in limited quantities may be shipped with appropriate markings and packaging, like an ORM-D label. Additionally, as a result of terrorism concerns, the U.S. Postal Service subjects their packages to numerous security tests, often scanning or x-raying packages for materials that might be found in biological materials or mail bombs.

Newspapers and magazines are also sent through postal services. Many magazines are simply placed in the mail normally (but in the U.S., they are printed with a special bar code that acts as pre-paid postage - see POSTNET), but many are now shipped in shrinkwrap to protect the loose contents of the magazine. During the second half of the 19th century and the first half of the 20th century, newspapers and magazines were normally posted using wrappers with a stamp imprint.

Hybrid mail, sometimes referred to as L-mail, is the electronic lodgement of mail from the mail generator's computer directly to a Postal Service provider. The Postal Service provider is then able to use electronic means to have the mail piece sorted, routed and physically produced at a site closest to the delivery point. It is a type of mail growing in popularity with some Post Office operations and individual businesses venturing into this market. In some countries, these services are available to print and deliver emails to those who are unable to receive email, such as the elderly or infirm. Services provided by Hybrid mail providers are closely related to that of mail forwarding service providers.

Collecting

Postage stamps are also object of a particular form of collecting. Stamp collecting has been a very popular hobby. In some cases, when demand greatly exceeds supply, their commercial value on this specific market may become enormously greater than face value, even after use. For some postal services the sale of stamps to collectors who will never use them is a significant source of revenue; for example, stamps from Tokelau, South Georgia & South Sandwich Islands, Tristan da Cunha, Niuafo´ou and many others. Stamp collecting is commonly known as philately, although strictly the latter term refers to the study of stamps.

Another form of collecting regards postcards, a document written on a single robust sheet of paper, usually decorated with photographic pictures or artistic drawings on one of the sides, and short messages on a small part of the other side, that also contained the space for the address. In strict philatelic usage, the postcard is to be distinguished from the postal card, which has a pre-printed postage on the card. The fact that this communication is visible by other than the receiver often causes the messages to be written in jargon.

Letters are often studied as an example of literature, and also in biography in the case of a famous person. A portion of the New Testament of the Bible is composed of the Apostle Paul's epistles to Christian congregations in various parts of the Roman Empire. See below for a list of famous letters.

A style of writing, called epistolary, tells a fictional story in the form of the correspondence between two or more characters.

A makeshift mail method after stranding on a deserted island is a message in a bottle.

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Plate commemorating the launching site of the first airmail carrier (1870) in Metz, France.

In the United States, private companies, such as FedEx and UPS, compete with the federal government's United States Postal Service, particularly in package delivery. Different mailboxes are also provided for local and express service. (The USPS has a legal monopoly on First Class and Standard Mail delivery.)

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Mail is part of the postal system. The postal system is a system where written documents and small to medium packages are sent (delivered) to places around the world. Anything sent through the postal system is called mail or post. A postal service can be private or public.

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A washing machine is a machine that washes dirty clothes. It contains a barrel into which the clothes are placed. This barrel is filled with water, and then rotated very quickly to make the water remove dirt from the clothes. Most washing machines are made so that detergent ( liquids or powders) can be put into the machine. These can help make the clothes cleaner.

Sometimes a washing machine and a clothes dryer are put together. Washing machines often use technology to change how you want to wash.

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In a top-loading washer, water circulates primarily along the poloidal axis during the wash cycle, as indicated by the red arrow in this illustration of a torus.

German laundry centrifuge to extract water from laundry. The advent of automatic washing machines with spin cycles made such specialized appliances largely obsolete by the 1970s.

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A washing machine is a machine that washes dirty clothes. It contains a barrel into which the clothes are placed. This barrel is filled with water, and then rotated very quickly to make the water remove dirt from the clothes. Most washing machines are made so that detergent ( liquids or powders) can be put into the machine.

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A kitchen stove, often called simply a stove or a cooker, is a kitchen appliance designed for the purpose of cooking food. Kitchen stoves rely on the application of direct heat for the cooking process and may also contain an oven, used for baking.

"Cookstoves" (also called "cooking stoves" or "wood stoves") are heated by burning wood or charcoal; "gas stoves" are heated by gas; and "electric stoves" by electricity. A stove with a built-in cooktop is also called a range.

In the industrialized world, as stoves replaced open fires and braziers as a source of more efficient and reliable heating, models were developed that could also be used for cooking, and these came to be known as kitchen stoves. When homes began to be heated with central heating systems, there was less need for an appliance that served as both heat source and cooker and stand-alone cookers replaced them. Cooker and stove are often used interchangeably.

The fuel-burning stove is the most basic design of kitchen stove. Nearly half of the people in the world, mainly in the developing world), burn biomass (wood, charcoal, crop residues, and dung) and coal in basic cook-stoves or open fires to cook their food. More fuel efficient and environmentally sound biomass cook stoves are being developed for use in these places.

Natural gas and electric stoves are the most common today in western countries. Both are equally effective and safe, and the choice between the two is largely a matter of personal preference and pre-existing utility outlets: if a house has no gas supply, adding one just to be able to run a gas stove can be expensive.

Modern kitchen stoves often have a "stove-top" or "cooktop" as well as an oven. A "drop-in range" is a combination stove-top and oven unit that installs in a kitchen's lower cabinets flush with the counter-top. Most modern stoves come in a unit with built-in extractor hoods.

Professional chefs often prefer gas stovetops, for they allow them to control the heat more finely and more quickly. Today's major brands offer both gas and electric stoves, and many also offer dual-fuel ranges combining a gas stove-top and an electric oven.

The modern kitchen range was invented by Sir Benjamin Thompson, Count Rumford in the 1790s. As an active scientist and prolific inventor, he put the study of heat onto a scientific basis and developed improvements for chimneys, fireplaces and industrial furnaces, which led to his invention of the kitchen range.

A gas stove was shown at The Great Exhibition in London in 1851, but it was only in the 1880s that the technology became a commercial success in England. By that stage a large and reliable network for gas pipeline transport had spread over much of the country, making gas relatively cheap and efficient for domestic use. Gas stoves only became widespread on the European Continent and in the United States in the early 20th century.

Once electric power was widely and economically available, electric stoves became a popular alternative to fuel-burning appliances. One of the earliest such devices was patented by Canadian inventor Thomas Ahearn in 1892. Ahearn was part owner of Ottawa's Chaudiere Electric Light and Power Company. The electric stove was showcased at the Chicago World's Fair in 1893, where an electrified model kitchen was shown.

Unlike the gas stove, the electrical stove was slow to catch on, partly due to the unfamiliar technology, and the need for cities and towns to be electrified. Early electric stoves were unsatisfactory due to the cost of electricity (compared with wood, coal, or city gas), limited power available from the electrical supply company, poor temperature regulation, and short life of heating elements. The invention of nichrome alloy for resistance wires improved the cost and durability of heating elements.

The first practical design was patented by the Australian David Curle Smith in 1905. His device is what later became the configuration for most electric stoves: an oven surmounted by a hotplate with a grill tray between them.

Microwave ovens were developed in the 1940s, and use microwave radiation to directly heat the water held inside food.

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Indonesian traditional brick stove, used in some rural areas

An 18th-century Japanese merchant's kitchen with copper Kamado (Hezzui), Fukagawa Edo Museum

A 19th-century stove made in Budapest exhibited in the Međimurje County Museum, Croatia

Early gas stoves produced by Windsor in Mrs Beeton's Book of Household Management, 1904.

Australian patent (1905) for an "electric cooking stove", also known as "The Kalgoorlie Stove".

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A kitchen stove, often called simply a stove or a cooker, is a kitchen appliance designed for the purpose of cooking food. Kitchen stoves rely on the application of direct heat for the cooking process and may also contain an oven, used for baking.

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A typewriter is a machine that is for typing on a piece of paper instead of writing by hand. It has keys for typing letters, numerals, and symbols one at a time. Typewriters were created in 1829. Typewriters were originally invented to make writing faster and printing. The earliest typing was done on stone, clay, or metal sheets by inscribing them.

A typewriter does not have computer memory. As with writing with a pen, it is difficult to correct mistakes. One advantage is that many of them are not electrical, so you do not need to plug them in. Hackers cannot see what you have typed. On many typewriters, a separate type element (called a typebar) corresponds to each key. The first commercial typewriters were introduced in 1874. They did not become common in offices until after the mid-1880s.

Typewriters quickly became a necessary tool for almost all writing other than personal handwritten letters. They were used a lot by professional writers, in offices, and for business correspondence in private homes. Typewriters were common in most offices up to the 1980s. After that, computers often replaced them. Nevertheless, typewriters are still common in some parts of the world. They are needed for a few specific applications, and they are popular in certain subcultures. Early typewriters, and later cheap ones, were "manual" typewriters. This means they were powered completely by the user. After the mid-20th century, electric typewriters with a motor became most common.

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An Elliott-Fisher book typewriter on display at the Historic Archive and Museum of Mining in Pachuca, Mexico

The " QWERTY" layout of typewriter keys became a de facto standard and continues to be used long after the reasons for its adoption (including reduction of key/lever entanglements) have ceased to apply.

This typed page uses a number of typographic conventions stemming from the mechanical limitations of the typewriter: two hyphens in place of an em dash, double sentence spacing, straight quotation marks, tab indents for paragraphs, and double carriage returns between paragraphs

Chinese typewriter at Deutsches Technikmuseum

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A typewriter is a machine that is for typing on a piece of paper instead of writing by hand. It has keys for typing letters, numerals, and symbols one at a time. Typewriters were created in 1829. Typewriters were originally invented to make writing faster and printing.

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A computer is a machine (mostly electronic) that is able to take information ( input), do some work on or make changes to the information (process), to make new information ( output). Computers have existed for much of human history. Examples of early computers are the astrolabe and the abacus. There are four main processing steps in a computer, and they are: inputting, outputting, storage and processing.

Modern computers are very different from early computers. They can do billions of calculations per second. Most people have used a personal computer in their home or at work. Computers do many different jobs where automation is useful. Some examples are controlling traffic lights, vehicle computers, security systems, washing machines and digital televisions.

A computer user can control it by a user interface. Input devices include keyboard, mouse, buttons, touch screen. Some very new computers can also be controlled with voice commands or hand gestures or even brain signals through electrodes implanted in the brain or along nerves.

Computers can be designed to do almost anything with information. Computers are used to control large and small machines which in the past were controlled by humans. They are also in homes, where they are used for things such as listening to music, reading the news, and writing.

Modern computers are electronic computer hardware but they are only useful if they also have software. The software uses the hardware when the user gives it instructions, and gives useful output.

Many modern computers do billions of calculations each second. They do mathematical arithmetic very quickly but computers do not really "think". They only follow the instructions in their software programs.

Computer programs are designed or written by computer programmers. A few programmers write programs in the computer's own language called machine code. Most programs are written using a programming language like C++, Java, and Python. These programming languages are more like the language you talk and write with every day. A program called a compiler translates the user's instructions into binary code (machine code) that the computer will understand and do what is needed.

History of computers

Definition

A computer is an electronic machine which helps in solving problems quickly and easily. It solves problems according to instructions given to it by the computer user called programs or software. It is a digital machine(that uses binary digits) used in all fields.

Automation

Humans have a problem with maths. To show this, try doing 584 x 3,220 in your head. It is hard to remember all the steps! People made tools to help them remember where they were in a maths problem. The other problem people have is that they have to do the same problem over and over and over again. A cashier had to make change every day in her head or with a piece of paper. That took a lot of time and made mistakes. So, people made calculators that did those same things over and over. This part of computer history is called the "history of automated calculation," which is a fancy phrase for "the history of machines that make it easy for me to do this same maths problem over and over without making mistakes."

The abacus, the slide rule, the astrolabe and the Antikythera mechanism (which dates from about 150-100 BC) are examples of automated calculation machines.

Programming

People did not want a machine that would do the same thing over and over again. For example, a music box is a machine that plays the same music over and over again. Some people wanted to be able to tell their machine to do different things. For example, they wanted to tell the music box to play different music every time. They wanted to be able to program the music box- to order the music box to play different music. This part of computer history is called the "history of programmable machines" which is a fancy phrase for "The history of machines that I can order to do different things if I know how to speak their language."

One of the first examples of this was built by Hero of Alexandria (c. 10-70 AD). He built a mechanical theater which performed a play lasting 10 minutes and was operated by a complex system of ropes and drums. These ropes and drums were the language of the machine- they told what the machine did and when. Some people argue that this is the first programmable machine.

Historians disagree on which early machines are "computers". Many say the "castle clock", an astronomical clock invented by Al-Jazari in 1206, is the first known programmable analog computer. Others say the first computer was made by Charles Babbage. Al - Jazari's showed the zodiac, the solar and lunar orbits, a crescent moon-shaped pointer travelling across a gateway that made some doors to open every hour, and five robotic musicians who play music when levers hit them. The length of day and night could be changed (AKA re-programmed) every day in order to account for the changing lengths of day and night throughout the year. Ada Lovelace is considered to be the first programmer.

The Computing Era

At the end of the Middle Ages, people in Europe thought math and engineering were more important. In 1623, Wilhelm Schickard made a mechanical calculator. Other Europeans made more calculators after him. They were not modern computers because they could only add, subtract, and multiply- you could not change what they did to make them do something like play Tetris. Because of this, we say they were not programmable.

In 1801, Joseph Marie Jacquard used punched paper cards to tell his textile loom what kind of pattern to weave. He could use punch cards to tell the loom what to do, and he could change the punch cards, which means he could program the loom to weave the pattern he wanted. This means the loom was programmable.

Charles Babbage wanted to make a similar machine that could calculate. He called it "The Analytical Engine". Because Babbage did not have enough money and always changed his design when he had a better idea, he never built his Analytical Engine.

As time went on, computers got more and more popular. And that stands out at the beginning. This is because people get bored easily doing the same thing over and over. Imagine spending your life writing things down on index cards, storing them, and then having to go find them again. The U.S. Census Bureau in 1890 had hundreds of people doing just that. People got bored and frustrated, and would say, "There HAS to be an easier way to do this." Then a clever person worked out how to make machines do a lot of the work. Herman Hollerith figured out how to make a machine that would automatically add up information that the Census bureau collected. The Computing Tabulating Recording Corporation (which later became IBM) made his machines, and everyone was happy. At least, they were happy until their machines broke down, got jammed, and had to be repaired. This is when the Computing Tabulating Recording Corporation invented tech support.

Because of machines like this, new ways of talking to these machines were invented, and new types of machines were invented, and eventually the computer as we know it was born.

Analog and Digital Computers

In the first half of the 20th century, scientists started using computers, mostly because scientists had a lot of math to figure out and wanted to spend more of their time thinking about the secrets of the universe instead of spending hours adding numbers together. For example, if they had to launch a rocket ship, they needed to do a lot of math to make sure the rocket worked right.

So they put together computers. These computers used analog circuits, which made them very hard to program. Then, in the 1930s, they invented digital computers, which made them easier to program.

High-scale computers

Scientists figured out how to make and use digital computers in the 1930s and 1940s. Scientists made a lot of digital computers, and as they did, they figured out how to ask them the right sorts of questions to get the most out of them. Here are a few of the computers they built:

Harvard Mark I - IBM ASCC (US)

1944

Electro-mechanical

Program-controlled by 24-channel punched paper tape (but no conditional branch)

No

Manchester Small-Scale Experimental Machine (UK)

June 1948
Electronic
Stored-program in Williams cathode ray tube memory

Yes

September 1948
Electronic
Program-controlled by patch cables and switches plus a primitive read-only stored programming mechanism using the Function Tables as program ROM

Yes

Manchester Mark 1 (UK)

October 1949
Electronic
Stored-program in Williams cathode ray tube memory and magnetic drum memory

Yes

Konrad Zuse's electromechanical "Z machines". The Z3 (1941) was the first working machine that used binary arithmetic. Binary arithmetic means using "Yes" and "No." to add numbers together. You could also program it. In 1998 the Z3 was proved to be Turing complete. Turing complete means that it is possible to tell this particular computer anything that it is mathematically possible to tell a computer. It is the world's first modern computer.

The non-programmable Atanasoff-Berry Computer (1941) which used vacuum tubes to store "yes" and "no" answers, and regenerative capacitor memory.

The Harvard Mark I (1944), A big computer that you could kind of program.

The U.S. Army's Ballistics Research Laboratory ENIAC (1946), which could add numbers the way people do (using the numbers 0 through 9) and is sometimes called the first general purpose electronic computer (since Konrad Zuse's Z3 of 1941 used electromagnets instead of electronics). At first, however, the only way to reprogram ENIAC was by rewiring it.

Several developers of ENIAC saw its problems. They invented a way to for a computer to remember what they had told it, and a way to change what it remembered. This is known as "stored program architecture" or von Neumann architecture. John von Neumann talked about this design in the paper First Draft of a Report on the EDVAC, distributed in 1945. A number of projects to develop computers based on the stored-program architecture started around this time. The first of these was completed in Great Britain. The first to be demonstrated working was the Manchester Small-Scale Experimental Machine (SSEM or "Baby"), while the EDSAC, completed a year after SSEM, was the first really useful computer that used the stored program design. Shortly afterwards, the machine originally described by von Neumann's paper- EDVAC -was completed but was not ready for two years.

Nearly all modern computers use the stored-program architecture. It has become the main concept which defines a modern computer. The technologies used to build computers have changed since the 1940s, but many current computers still use the von-Neumann architecture.

In the 1950s computers were built out of mostly vacuum tubes. Transistors replaced vacuum tubes in the 1960s because they were smaller and cheaper. They also need less power and do not break down as much as vacuum tubes. In the 1970s, technologies were based on integrated circuits. Microprocessors, such as the Intel 4004 made computers smaller, cheaper, faster and more reliable. By the 1980s, microcontrollers became small and cheap enough to replace mechanical controls in things like washing machines. The 1980s also saw home computers and personal computers. With the evolution of the Internet, personal computers are becoming as common as the television and the telephone in the household.

In 2005 Nokia started to call some of its mobile phones (the N-series) "multimedia computers" and after the launch of the Apple iPhone in 2007, many are now starting to add the smartphone category among "real" computers. In 2008, if smartphones are included in the numbers of computers in the world, the biggest computer maker by units sold, was no longer Hewlett-Packard, but rather Nokia.

Kinds of computers

There are many types of computers:

A "desktop computer" is a small machine that has a screen (which is not part of the computer). Most people keep them on top of a desk, which is why they are called "desktop computers." " Laptop computers" are computers small enough to fit on your lap. This makes them easy to carry around. Both laptops and desktops are called personal computers, because one person at a time uses them for things like playing music, surfing the web, or playing video games.

There are bigger computers that many people at a time can use. These are called "Mainframes," and these computers do all the things that make things like the internet work. You can think of a personal computer like this: the personal computer is like your skin: you can see it, other people can see it, and through your skin you feel wind, water, air, and the rest of the world. A mainframe is more like your internal organs: you never see them, and you barely even think about them, but if they suddenly went missing, you would have some very big problems.

An embedded computer, also called embedded system is a computer that does one thing and one thing only, and usually does it very well. For example, an alarm clock is an embedded computer: it tells the time. Unlike your personal computer, you cannot use your clock to play Tetris. Because of this, we say that embedded computers cannot be programmed, because you cannot install more programs on your clock. Some mobile phones, automatic teller machines, microwave ovens, CD players and cars are operated by embedded computers.

All-in-one PC

All-in-one computers are desktop computers that have all of the computer's inner mechanisms in the same case as the monitor. Apple has made several popular examples of all-in-one computers, such as the original Macintosh of the mid-1980s and the iMac of the late 1990s and 2000s.

Common uses of home computers

Common uses of work computers

Word processing

Spreadsheets

PowerPoint Presentations

Photo Editing (Photoshop, GIMP)

E-mail

Video editing/rendering/encoding

Audio recording

System Management

Excel

Working methods

Computers store data and the instructions as numbers, because computers can do things with numbers very quickly. These data are stored as binary symbols (1s and 0s). A 1 or a 0 symbol stored by a computer is called a bit, which comes from the words binary digit. Computers can use many bits together to represent instructions and the data that these instructions use. A list of instructions is called a program and is stored on the computer's hard disk. Computers work through the program by using a central processing unit, and they use fast memory called RAM as a space to store the instructions and data while they are doing this. When the computer wants to store the results of the program for later, it uses the hard disk because things stored on a hard disk can still be remembered after the computer is turned off.

An operating system tells the computer how to understand what jobs it has to do, how to do these jobs, and how to tell people the results. Millions of computers may be using the same operating system, while each computer can have its own application programs to do what its user needs. Using the same operating systems makes it easy to learn how to use computers for new things. A user who needs to use a computer for something different, can learn how to use a new application program. Some operating systems can have simple command lines or a fully user-frendly GUI.

The Internet

One of the most important jobs that computers do for people is helping with communication. Communication is how people share information. Computers have helped people move forward in science, medicine, business, and learning, because they let experts from anywhere in the world work with each other and share information. They also let other people communicate with each other, do their jobs almost anywhere, learn about almost anything, or share their opinions with each other. The Internet is the thing that lets people communicate between their computers.

Computers and waste

A computer is now almost always an electronic device. It usually contains materials that will become toxic waste when disposed of. When a new computer is bought in some places, laws require that the cost of its waste management must also be paid for. This is called product stewardship.

Computers can become obsolete quickly, depending on what programs the user runs. Very often, they are thrown away within two or three years, because newer programs require a more powerful computer. This makes the problem worse, so computer recycling happens a lot. Many projects try to send working computers to developing nations so they can be re-used and will not become waste as quickly, as most people do not need to run new programs. Some computer parts, such as hard drives, can break easily. When these parts end up in the landfill, they can put poisonous chemicals like lead into the ground water. Hard drives can also contain secret information like credit card numbers. If the hard drive is not erased before being thrown away, an identity thief can get the information off of the hard drive, even if the drive doesn't work, and use it to steal money from the previous owner's bank account.

Main hardware

Computers come in different forms, but most of them have a common design.

All computers have a CPU.

All computers have some kind of data bus which lets them get inputs or output things to the environment.

All computers have some form of memory. These are usually chips (integrated circuits) which can hold information.

Many computers have some kind of sensors, which lets them get input from their environment.

Many computers have some kind of display device, which lets them show output. They may also have other peripheral devices connected.

A computer has several main parts. When comparing a computer to a human body, the CPU is like a brain. It does most of the 'thinking' and tells the rest of the computer how to work. The CPU is on the Motherboard, which is like the skeleton. It provides the basis for where the other parts go, and carries the nerves that connect them to each other and the CPU. The motherboard is connected to a power supply, which provides electricity to the entire computer. The various drives ( CD drive, floppy drive, and on many newer computers, USB flash drive) act like eyes, ears, and fingers, and allow the computer to read different types of storage, in the same way that a human can read different types of books. The hard drive is like a human's memory, and keeps track of all the data stored on the computer. Most computers have a sound card or another method of making sound, which is like vocal cords, or a voice box. Connected to the sound card are speakers, which are like a mouth, and are where the sound comes out. Computers might also have a graphics card, which helps the computer to create visual effects, such as 3D environments, or more realistic colors, and more powerful graphics cards can make more realistic or more advanced images, in the same way a well trained artist can.

Largest Computer Companies

Images for kids

ENIAC was the first electronic, Turing-complete device, and performed ballistics trajectory calculations for the United States Army.

A 1970s punched card containing one line from a FORTRAN program. The card reads: "Z(1) = Y + W(1)" and is labeled "PROJ039" for identification purposes.

Women as computers in NACA High Speed Flight Station "Computer Room"

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A computer is a machine (mostly electronic) that is able to take information ( input), do some work on or make changes to the information (process), to make new information ( output). Computers have existed for much of human history. Examples of early computers are the astrolabe and the abacus.

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John Logie Baird FRSE (13 August 1888 - 14 June 1946) was a Scottish engineer, innovator, one of the inventors of the mechanical television, demonstrating the first working television system on 26 January 1926, and inventor of both the first publicly demonstrated colour television system, and the first purely electronic colour television picture tube.

In 1928 the Baird Television Development Company achieved the first transatlantic television transmission. Baird's early technological successes and his role in the practical introduction of broadcast television for home entertainment have earned him a prominent place in television's history.

Baird was ranked number 44 in the BBC's list of the 100 Greatest Britons following a UK-wide vote in 2002. In 2006, Baird was named as one of the 10 greatest Scottish scientists in history, having been listed in the National Library of Scotland's 'Scottish Science Hall of Fame'. In 2015 he was inducted into the Scottish Engineering Hall of Fame.

Early years

Baird was born in Helensburgh, Dunbartonshire, and was the youngest of four children of the Reverend John Baird, the Church of Scotland's minister for the local St Bride's Church and Jessie Morrison Inglis, the orphaned niece of a wealthy family of shipbuilders from Glasgow.

He was educated at Larchfield Academy (now part of Lomond School) in Helensburgh; the Glasgow and West of Scotland Technical College; and the University of Glasgow. While at college Baird undertook a series of engineering apprentice jobs as part of his course. The conditions in industrial Glasgow at the time helped form his socialist convictions but also contributed to his ill health. He became an agnostic, though this did not strain his relationship with his father. His degree course was interrupted by the First World War and he never returned to graduate.

At the beginning of 1915 he volunteered for service in the British Army but was classified as unfit for active duty. Unable to go to the Front, he took a job with the Clyde Valley Electrical Power Company, which was engaged in munitions work.

Television experiments

The development of television was the result of work by many inventors. Among them, Baird was a prominent pioneer and made major advances in the field. Many historians credit Baird with being the first to produce a live, moving, greyscale television image from reflected light. Baird achieved this, where other inventors had failed, by obtaining a better photoelectric cell and improving the signal conditioning from the photocell and the video amplifier.

Baird gave the first public demonstration of moving silhouette images by television at Selfridges department store in London in a three-week series of demonstrations beginning on 25 March 1925.

In his laboratory on 2 October 1925, Baird successfully transmitted the first television picture with a greyscale image: the head of a ventriloquist's dummy nicknamed "Stooky Bill" in a 30-line vertically scanned image, at five pictures per second. Baird went downstairs and fetched an office worker, 20-year-old William Edward Taynton, to see what a human face would look like, and Taynton became the first person to be televised in a full tonal range.

First public demonstrations

On 26 January 1926, Baird repeated the transmission for members of the Royal Institution and a reporter from in his laboratory at 22 Frith Street in the Soho district of London. By this time, he had improved the scan rate to 12.5 pictures per second. It was the first demonstration of a television system that could broadcast live moving images with tone graduation.

He demonstrated the world's first colour transmission on 3 July 1928. The demonstration was of a young girl wearing different coloured hats. Noele Gordon went on to become a successful TV actress, famous for the soap opera Crossroads. That same year he also demonstrated stereoscopic television.

Broadcasting

In 1927, Baird made a signal go over 438 miles (705 km) between London and Glasgow; Baird sent the world's first long-distance television pictures to the Central Hotel at Glasgow Central Station.

Baird then started the Baird Television Development Company Ltd, and in 1928 it made the first transatlantic television transmission, from London to Hartsdale, New York, and the first television programme for the BBC, his television systems were replaced by the electronic television system developed by EMI-Marconi.

Baird did lots of work for the field of electronic television after mechanical systems stopped being used. In 1939, he showed colour television using a cathode ray tube.

Other inventions

Some of Baird's early inventions did not work. In his twenties he tried to make diamonds by heating graphite and ruined Glasgow's electricity supply. Later Baird made a glass razor which did not get rusty, but it shattered.

Later years

From December 1944, Logie Baird lived at 1 Station Road, Bexhill-on-Sea, East Sussex, immediately north of the station and subsequently died there on 14 June 1946 after suffering a stroke in February. The house was demolished in 2007 and the site is now apartments named Baird Court. Logie Baird is buried with his mother, father and wife in Helensburgh Cemetery, Argyll, Scotland.

Honours and portrayals

Australian television's Logie Awards were named in honour of John Logie Baird's contribution to the invention of the television. Baird became the only deceased subject of This Is Your Life when he was honoured by Eamonn Andrews at the BBC Television Theatre in 1957.

He was played by Michael Gwynn (and also by Andrew Irvine, who played him as a boy) in the 1957 TV film A Voice in Vision and by Robert McIntosh in the 1986 TV drama The Fools on the Hill.

In 2014, the Society of Motion Picture and Television Engineers (SMPTE) inducted Logie Baird into The Honor Roll, which "posthumously recognizes individuals who were not awarded Honorary Membership during their lifetimes but whose contributions would have been sufficient to warrant such an honor".

On 26 January 2016, the search engine Google released a Google Doodle to mark the 90th anniversary of Logie Baird's first public demonstration of live television.

Images for kids

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John Logie Baird FRSE (13 August 1888 - 14 June 1946) was a Scottish engineer, innovator, one of the inventors of the mechanical television, demonstrating the first working television system on 26 January 1926, and inventor of both the first publicly demonstrated colour television system, and the first purely electronic colour television picture tube.

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Eastman Kodak Company was started by George Eastman and Henry A. Strong in 1881. They made their headquarters in Rochester, New York. It began as the Eastman Dry plate company. The company made Photographic plates for Photographers. It changed from a partnership to a corporation in 1884. In 1888 it changed its name again to the Eastman Kodak Company. This is when they released their first hand-held camera called the Kodak. It used a roll of photographic film which the company had started making in 1885. It was a camera simple enough for anyone to take pictures. Eastman Kodak re- invented photography and became an American success story. But their success would not last.

At first photographers used glass plates they had to coat with an emulsion. But they had to be used within minutes of being coated. They also had to be processed into a picture right away. In 1878, Eastman successfully created dry plates that could be coated with a gelatin solution. These could be used at the photographer's convenience. They did not require all the heavy equipment wet plates did. Eastman decided to go into business selling them. He invented a machine to mass-produce dry plates. In 1888, the company sold the first Kodak box cameras. The slogan was "you press the button, we do the rest". For $24 USD the camera came already loaded with film capable of taking 100 pictures. The camera was sent back to the factory where for $10 the film was developed into pictures. These cameras first used paper film but later turned to Nitrocellulose film. An indexing roller to hold film was invented by David Houston. It had square holes in the edge of the film to advance the film with no waste or Multiple exposures. But Eastman did not want to pay to license his patent. So they bought his patent in 1899. Kodak kept making dry plates until that market dried up. Their main profit was in film and film developing papers and chemicals. They made film for the movie industry, 16mm film for hobby filmmaking and cameras of all kinds. In the mid- 1920s they came out with color film. In 1929 Kodak created motion picture film for adding sound to motion pictures.

In 1947 Edward Land invented the Polaroid instant camera. The camera could develop its own pictures inside the camera in 60 seconds. Within five years Polaroid sold over a million cameras. Kodak took notice. Since Kodak held 80% of the market for photographic development, instant cameras were a real threat. Kodak quickly came out with their own instant camera. Land sued Kodak for $12 billion for using its technology. In the end Land won and Koday quit making instant cameras. But they won only a fraction of what they sued Kodak for and eventually went out of business in 2001.

Fujifilm, the Japanese photography company, began selling inexpensive film in the United States in the 1980s. Since their film cost much less than Kodak's, by 1999 they had a large share of the film market. Kodak lost millions of dollars and had many layoffs. When Digital cameras became popular, Kodak quickly joined that market. By 1999 they were the second largest maker of digital cameras. But they lost $60 on each one they sold.

Kodak made so many marketing mistakes that its stock dropped from $76 a share in 1999 to $25 in 2004. They dropped out of the film manufacturing business. Finally Kodak was dropped from the Dow Jones Industrial Average. In 2012 the 131-year-company filed for bankruptcy. After selling off many of its products to other companies, Kodak came out of bankruptcy a much smaller company.

Images for kids

An advertisement from The Photographic Herald and Amateur Sportsman (November 1889)

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Eastman Kodak Company was started by George Eastman and Henry A. Strong in 1881. They made their headquarters in Rochester, New York. It began as the Eastman Dry plate company. The company made Photographic plates for Photographers. It changed from a partnership to a corporation in 1884.

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A wheel is a disc- or circle-shaped mechanical device. Its main purpose is to allow things to roll; in other words, the wheel spins, and objects on the wheels move more easily along the ground. It is a simple machine.

Most experts believe the ancient Mesopotamians invented the wheel about 3500 BC. In addition, the Asia discovered it on their own around 3500 BC. The Inca and Maya had wheels on children's toys around 1500 BC, but they did not use wheels for work. Africa south of the Sahara desert, Europe, and Australia did not have the wheel until people there met people from other cultures.

Modern Uses

Today, wheels are used in cars, carts, airplanes, wheelchairs, bicycles, trains, caravans and skateboards, in addition to many more devices. Wheels are usually used in pairs,connected by a rod of wood or metal known as an axle.

Images for kids

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A wheel is a disc- or circle-shaped mechanical device. Its main purpose is to allow things to roll; in other words, the wheel spins, and objects on the wheels move more easily along the ground. It is a simple machine. Most experts believe the ancient Mesopotamians invented the wheel about 3500 BC.

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The early history of the automobile can be divided into a number of eras, based on method of propulsion. Later periods were defined by trends in exterior styling, size, and utility preferences. The question of who invented the first automobile depends on how you define the words "automobile" and "invent". The history of the automobile is rich and varied. It goes back to Leonardo da Vinci in the 15th century who created early designs and models of transportation vehicles.

Early pioneers

In 1807 François Isaac de Rivaz designed the first hydrogen-powered internal combustion engine. In 1813 he built a car 6 metres (20 ft) long and weighing over 1 metric ton (0.98 long tons; 1.1 short tons).

Between 1832 and 1839, Robert Anderson built the first electric-powered carriage in Scotland.

In 1864 Siegfried Marcus built the first gasoline powered internal combustion engine. In 1870 he placed it on a pushcart making it the first four wheeled gasoline-powered vehicle. He built four more combustion-engine cars over a 10-to-15-year span that influenced later cars. Marcus created the two-cycle combustion engine. The car's second version in 1880 introduced a four-cycle, gasoline-powered engine. It had an ingenious carburetor design, and magneto ignition. He created an additional two models further refining his design with steering, a clutch, and brakes. His second car is on display at the Technical Museum in Vienna. During his lifetime, he was honored as the originator of the motorcar. But his place in history was all but erased by the Nazis during World War II. Because Marcus was of Jewish descent, the Nazi propaganda office ordered his work to be destroyed, his name expunged from future textbooks, and his public memorials removed. They gave credit instead to Karl Benz.

In 1885-1886, Karl Benz developed a petrol- or gasoline-powered automobile. It was called the Benz Patent-Motorwagen. This is also considered to be the first "production" automobile.

In 1886, Gottlieb Daimler built the first four-wheeled, four-stroke engine called the "Cannstatt-Daimler."

In 1893, Charles Duryea and his brother J. Frank Duryea built the first successful gasoline-powered car with a two-stroke engine. The two brothers set up the first American car manufacturing company.

In 1895, George Baldwin Selden received the patent for the combined internal-combustion engine with a carriage. He never produced the vehicle and only seldom collected royalties for using his patent.

In 1908, Henry Ford began producing affordable, simple and reliable cars anyone could drive.

Evolution of the automobile

Invention era

This is the period starts with the car made by Karl Benz in 1885. There were earlier inventions that used mainly steam-power to move the vehicles but the Benz car was the first to use a gasoline powered internal combustion engine in what could be called an automobile. The period goes up to the start of the production of Henry Ford's Model T.

Manufacturing era

This period dates from 1908 to 1914 and the beginning of World War I. While earlier designs were more ornamental, vehicles from this period are simpler and more affordable. It is the time when hundreds of smaller automobile manufacturers were trying to compete for attention and sales. A number of improvements were developed during this time. These include the electric ignition system, four-wheel brakes and the independent suspension. Transmissions were adopted. Along with throttle controls, these allowed the vehicles to travel at a number of speeds depending on conditions.

Coachwork era

From about 1920 to 1930, car manufacturers began creating a closed body on the vehicle. This protected the driver and passengers from the weather. Vehicles began using curved glass and the new enclosed bodies gave a sense of privacy. Heaters were added for comfort. Many of the features of modern cars came from this period. These include four-wheel drive, front-wheel drive, and hybrid electric vehicles. Safety glass protected those inside the car from sharp glass in cases of an accident. By the end of the 1920s cars were becoming faster and were showing a level of style and beauty.

Classic era

The classic era began about 1930 during the Great Depression and ended just before World War II. The Great Depression was a time when many in the United States were just trying to survive. But it is also the era of some of the most significant improvements to the automobile. Cars took on a great deal of style and sophistication. They became works of art in many cases.

Many new features were introduced during this era including the automatic transmission, the V-8, the V-12 and the V-16 engines. The gearshift lever moved to the steering column, hydraulic brakes were introduced for faster stopping and cars got trunks to carry luggage and cargo.

The car industry changed during the 1930s. It saw the rise of the Big Three automakers. These were General Motors, Ford Motor Company and Chrysler. They were able to successfully design and sell cars during the Great Depression when fewer people could afford a new car.

Integration period

In 1949, the automobile industry finally got back on its feet after World War II. This same year General Motors, Cadillac and Oldsmobile introduced the integrated one-piece automobile body. The process joined all the different parts of the body into one body shell. Cars produced during this period concentrated on safety. Cars were big during this time. But in the late 1960s carmakers tried to market much smaller cars. The attempts by General Motors, Chrysler and Ford were all marketing failures. Instead, what sold was the performance car. Cars like the Ford Mustang and the Plymouth Barracuda were very successful. During the late 1950s, many smaller countries began producing cars. Both India and Iran were making cars from about 1959. The first Indian car design from 1950 was very similar to the Opel Kapitän. The first Iranian cars were very similar to several American cars. Both were designed in the United Kingdom.

This period started about 1968 and continues to today. Body styles changed dramatically. The three most popular are the hatchback, the Minivan and the Sport utility vehicle (SUV). Starting in the Integration period, car manufacturers began designing cars for men while others are designed to attract women. The body shapes, colors and other cues are designed to appeal to a particular sex.

Today, women tend to prefer crossovers more than men. Examples are the Kia Sportage and the Honda CR-V. Men seem to prefer powerful cars like the Chevrolet Camaro and the GMC Sierra pickup truck. In car colors, men seem to prefer brighter colors while more women seem to prefer traditional neutral colors.

Related pages

Images for kids

German Flocken Elektrowagen of 1888, regarded as the first electric car of the world

In My Merry Oldsmobile songbook featuring an Oldsmobile Curved Dash automobile (produced 1901-1907) and period driving clothing

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History of the automobile Facts for Kids

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The early history of the automobile can be divided into a number of eras, based on method of propulsion. Later periods were defined by trends in exterior styling, size, and utility preferences. The question of who invented the first automobile depends on how you define the words "automobile" and "invent".

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A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, is a device for the mechanical recording and reproduction of sound. The sound vibration waveforms are recorded as corresponding physical deviations of a spiral groove engraved, etched, incised, or impressed into the surface of a rotating cylinder or disc, called a "record". To recreate the sound, the surface is similarly rotated while a playback stylus traces the groove and is therefore vibrated by it, very faintly reproducing the recorded sound. In early acoustic phonographs, the stylus vibrated a diaphragm which produced sound waves which were coupled to the open air through a flaring horn, or directly to the listener's ears through stethoscope-type earphones.

The phonograph was invented in 1877 by Thomas Edison. Alexander Graham Bell's Volta Laboratory made several improvements in the 1880s and introduced the graphophone, including the use of wax-coated cardboard cylinders and a cutting stylus that moved from side to side in a zigzag groove around the record. In the 1890s, Emile Berliner initiated the transition from phonograph cylinders to flat discs with a spiral groove running from the periphery to near the center, coining the term gramophone for disc record players, which is predominantly used in many languages. Later improvements through the years included modifications to the turntable and its drive system, the stylus or needle, and the sound and equalization systems.

The disc phonograph record was the dominant audio recording format throughout most of the 20th century. In the 1980s, phonograph use on a standard record player declined sharply due to the rise of the cassette tape, compact disc, and other digital recording formats. However, records are still a favorite format for some audiophiles, DJs, collectors, and turntablists (particularly in hip hop and electronic dance music), and have undergone a revival since the 2000s.

Terminology

Usage of terminology is not uniform across the English-speaking world (see below). In more modern usage, the playback device is often called a "turntable", "record player", or "record changer", although each of these terms denote categorically distinct items. When used in conjunction with a mixer as part of a DJ setup, turntables are often colloquially called "decks". In later electric phonographs (more often known since the 1940s as record players or, most recently, turntables), the motions of the stylus are converted into an analogous electrical signal by a transducer, then converted back into sound by a loudspeaker.

The term phonograph ("sound writing") was derived from the Greek words φωνή ( phonē, "sound" or "voice") and γραφή ( graphē, "writing"). The similar related terms gramophone (from the Greek γράμμα gramma "letter" and φωνή phōnē "voice") and graphophone have similar root meanings. The roots were already familiar from existing 19th-century words such as photograph ("light writing"), ("distant writing"), and ("distant sound"). The new term may have been influenced by the existing words phonographic and phonography, which referred to a system of phonetic shorthand; in 1852 The New York Times carried an advertisement for "Professor Webster's phonographic class", and in 1859 the New York State Teachers Association tabled a motion to "employ a phonographic recorder" to record its meetings.

Arguably, any device used to record sound or reproduce recorded sound could be called a type of "phonograph", but in common practice the word has come to mean historic technologies of sound recording, involving audio-frequency modulations of a physical trace or groove. In the late-19th and early-20th centuries, "Phonograph", "Gramophone", "Graphophone", "Zonophone", "Graphonole" and the like were still brand names specific to various makers of sometimes very different (i.e. cylinder and disc) machines; so considerable use was made of the generic term "talking machine", especially in print. "Talking machine" had earlier been used to refer to complicated devices which produced a crude imitation of speech, by simulating the workings of the vocal cords, tongue, and lips - a potential source of confusion both then and now.

United Kingdom

In British English, "gramophone" may refer to any sound-reproducing machine using disc records, which were introduced and popularized in the UK by the Gramophone Company. Originally, "gramophone" was a proprietary trademark of that company and any use of the name by competing makers of disc records was vigorously prosecuted in the courts, but in 1910 an English court decision decreed that it had become a generic term; it has been so used in the UK and most Commonwealth countries ever since. The term "phonograph" was usually restricted to machines that used cylinder records.

"Gramophone" generally referred to a wind-up machine. After the introduction of the softer vinyl records, 33-rpm LPs (long-playing records) and 45-rpm "single" or two-song records, and EPs (extended-play recordings), the common name became "record player" or "turntable". Often the home record player was part of a system that included a radio ( radiogram) and, later, might also play audiotape cassettes. From about 1960, such a system began to be described as a "hi-fi" (high-fidelity, monophonic) or a "stereo" (most systems being stereophonic by the mid-1960s).

United States

In American English, "phonograph", properly specific to machines made by Edison, was sometimes used in a generic sense as early as the 1890s to include cylinder-playing machines made by others. But it was then considered strictly incorrect to apply it to Emile Berliner's upstart Gramophone, a very different machine which played discs (although Edison's original Phonograph patent included the use of discs). "Talking machine" was the comprehensive generic term, but from about 1902 on, the general public was increasingly applying the word "phonograph" indiscriminately to both cylinder and disc machines and to the records they played. By the time of the First World War, the mass advertising and popularity of the Victrola (a line of disc-playing machines characterized by their concealed horns) sold by the Victor Talking Machine Company was leading to widespread generic use of the word "victrola" for any machine that played discs, which were generally called "phonograph records" or simply "records", but almost never "Victrola records".

After electrical disc-playing machines appeared on the market in the late 1920s, often combined with a radio receiver, the term "record player" was increasingly favored by the public. Manufacturers, however, typically advertised such combinations as "radio-phonographs". Portable record players (no radio included), with a latched cover and an integrated power amplifier and loudspeaker, were becoming popular as well, especially in schools and for use by children and teenagers.

In the years following the Second World War, as "hi-fi" (high-fidelity, monophonic) and, later, "stereo" ( stereophonic) component sound systems slowly evolved from an exotic specialty item into a common feature of American homes, the description of the record-spinning component as a "record changer" (which could automatically play through a stacked series of discs) or a "turntable" (which could hold only one disc at a time) entered common usage. By the 1980s, the use of a "record changer" was widely disparaged. So, the "turntable" emerged triumphant and retained its position to the present. Through all these changes, however, the discs have continued to be known as "phonograph records" or, much more commonly, simply as "records".

Gramophone, as a brand name, was not used in the United States after 1902, and the word quickly fell out of use there, although it has survived in its nickname form, Grammy, as the name of the Grammy Awards. The Grammy trophy itself is a small rendering of a gramophone, resembling a Victor disc machine with a taper arm.

Modern amplifier-component manufacturers continue to label the input jack which accepts the output from a modern magnetic pickup cartridge as the "phono" input, abbreviated from "phonograph".

In Australian English, "record player" was the term; "turntable" was a more technical term; "gramophone" was restricted to the old mechanical (i.e., wind-up) players; and "phonograph" was used as in British English. The "phonograph" was first demonstrated in Australia on 14 June, 1878 to a meeting of the Royal Society of Victoria by the Society's Honorary Secretary, Alex Sutherland who published "The Sounds of the Consonants, as Indicated by the Phonograph" in the Society's journal in November that year. On 8 August, 1878 the phonograph was publicly demonstrated at the Society's annual conversazione, along with a range of other new inventions, including the microphone.

Early history

Predecessors to the phonograph

Phonautograph

In 2008, phonautograph recordings made by Scott were played back as sound by American audio historians, who used optical scanning and computer processing to convert the traced waveforms into digital audio files. These recordings, made circa 1860, include fragments of two French songs and a recitation in Italian.

Paleophone

Charles Cros, a French poet and amateur scientist, is the first person known to have made the conceptual leap from recording sound as a traced line to the theoretical possibility of reproducing the sound from the tracing and then to devising a definite method for accomplishing the reproduction. On April 30, 1877, he deposited a sealed envelope containing a summary of his ideas with the French Academy of Sciences, a standard procedure used by scientists and inventors to establish priority of conception of unpublished ideas in the event of any later dispute.

Cros proposed the use of photoengraving, a process already in use to make metal printing plates from line drawings, to convert an insubstantial phonautograph tracing in soot into a groove or ridge on a metal disc or cylinder. This metal surface would then be given the same motion and speed as the original recording surface. A stylus linked to a diaphragm would be made to ride in the groove or on the ridge so that the stylus would be moved back and forth in accordance with the recorded vibrations. It would transmit these vibrations to the connected diaphragm, and the diaphragm would transmit them to the air.

An account of his invention was published on October 10, 1877, by which date Cros had devised a more direct procedure: the recording stylus could scribe its tracing through a thin coating of acid-resistant material on a metal surface and the surface could then be etched in an acid bath, producing the desired groove without the complication of an intermediate photographic procedure. The author of this article called the device a "phonographe", but Cros himself favored the word "paleophone", sometimes rendered in French as "voix du passé" (voice of the past).

Cros was a poet of meager means, not in a position to pay a machinist to build a working model, and largely content to bequeath his ideas to the public domain free of charge and let others reduce them to practice, but after the earliest reports of Edison's presumably independent invention crossed the Atlantic he had his sealed letter of April 30 opened and read at the December 3, 1877 meeting of the French Academy of Sciences, claiming due scientific credit for priority of conception.

Throughout the first decade (1890-1900) of commercial production of the earliest crude disc records, the direct acid-etch method first invented by Cros was used to create the metal master discs, but Cros was not around to claim any credit or to witness the humble beginnings of the eventually rich phonographic library he had foreseen. He had died in 1888 at the age of 45.

The early phonographs

Thomas Alva Edison conceived the principle of recording and reproducing sound between May and July 1877 as a byproduct of his efforts to "play back" recorded telegraph messages and to automate speech sounds for transmission by telephone. His first experiments were with waxed paper. He announced his invention of the first phonograph, a device for recording and replaying sound, on November 21, 1877 (early reports appear in Scientific American and several newspapers in the beginning of November, and an even earlier announcement of Edison working on a 'talking-machine' can be found in the Chicago Daily Tribune on May 9), and he demonstrated the device for the first time on November 29 (it was patented on February 19, 1878 as US Patent 200,521). "In December, 1877, a young man came into the office of the SCIENTIFIC AMERICAN, and placed before the editors a small, simple machine about which very few preliminary remarks were offered. The visitor without any ceremony whatever turned the crank, and to the astonishment of all present the machine said: "Good morning. How do you do? How do you like the phonograph?" The machine thus spoke for itself, and made known the fact that it was the phonograph..."

Edison presented his own account of inventing the phonograph:

I was experimenting," he said, "on an automatic method of recording telegraph messages on a disk of paper laid on a revolving platen, exactly the same as the disk talking-machine of to-day. The platen had a spiral groove on its surface, like the disk. Over this was placed a circular disk of paper; an electromagnet with the embossing point connected to an arm traveled over the disk; and any signals given through the magnets were embossed on the disk of paper. If this disc was removed from the machine and put on a similar machine provided with a contact point, the embossed record would cause the signals to be repeated into another wire. The ordinary speed of telegraphic signals is thirty-five to forty words a minute; but with this machine several hundred words were possible.

From my experiments on the telephone I knew of how to work a pawl connected to the diaphragm; and this engaging a ratchet-wheel served to give continuous rotation to a pulley. This pulley was connected by a cord to a little paper toy representing a man sawing wood. Hence, if one shouted: ' Mary had a little lamb,' etc., the paper man would start sawing wood. I reached the conclusion that if I could record the movements of the diaphragm properly, I could cause such records to reproduce the original movements imparted to the diaphragm by the voice, and thus succeed in recording and reproducing the human voice.
Instead of using a disk I designed a little machine using a cylinder provided with grooves around the surface. Over this was to be placed tinfoil, which easily received and recorded the movements of the diaphragm. A sketch was made, and the piece-work price, $18, was marked on the sketch. I was in the habit of marking the price I would pay on each sketch. If the workman lost, I would pay his regular wages; if he made more than the wages, he kept it. The workman who got the sketch was John Kruesi. I didn't have much faith that it would work, expecting that I might possibly hear a word or so that would give hope of a future for the idea. Kruesi, when he had nearly finished it, asked what it was for. I told him I was going to record talking, and then have the machine talk back. He thought it absurd. However, it was finished, the foil was put on; I then shouted 'Mary had a little lamb', etc. I adjusted the reproducer, and the machine reproduced it perfectly. I was never so taken aback in my life. Everybody was astonished. I was always afraid of things that worked the first time. Long experience proved that there were great drawbacks found generally before they could be got commercial; but here was something there was no doubt of.

The music critic Herman Klein attended an early demonstration (1881-2) of a similar machine. On the early phonograph's reproductive capabilities he writes "It sounded to my ear like someone singing about half a mile away, or talking at the other end of a big hall; but the effect was rather pleasant, save for a peculiar nasal quality wholly due to the mechanism, though there was little of the scratching which later was a prominent feature of the flat disc. Recording for that primitive machine was a comparatively simple matter. I had to keep my mouth about six inches away from the horn and remember not to make my voice too loud if I wanted anything approximating to a clear reproduction; that was all. When it was played over to me and I heard my own voice for the first time, one or two friends who were present said that it sounded rather like mine; others declared that they would never have recognised it. I daresay both opinions were correct."

The Argus (Melbourne) newspaper reported on an 1878 demonstration at the Royal Society of Victoria, writing "There was a large attendance of ladies and gentlemen, who appeared greatly interested in the various scientific instruments exhibited. Among these the most interesting, perhaps, was the trial made by Mr. Sutherland with the phonograph, which was most amusing. Several trials were made, and were all more or less successful. "Rule Britannia" was distinctly repeated, but great laughter was caused by the repetition of the convivial song of "He's a jolly good fellow," which sounded as if it was being sung by an old man of 80 with a very cracked voice."

Early machines

Edison's early phonographs recorded onto a thin sheet of metal, normally tinfoil, which was temporarily wrapped around a helically grooved cylinder mounted on a correspondingly threaded rod supported by plain and threaded bearings. While the cylinder was rotated and slowly progressed along its axis, the airborne sound vibrated a diaphragm connected to a stylus that indented the foil into the cylinder's groove, thereby recording the vibrations as "hill-and-dale" variations of the depth of the indentation.

Playback was accomplished by exactly repeating the recording procedure, the only difference being that the recorded foil now served to vibrate the stylus, which transmitted its vibrations to the diaphragm and onward into the air as audible sound. Although Edison's very first experimental tinfoil phonograph used separate and somewhat different recording and playback assemblies, in subsequent machines a single diaphragm and stylus served both purposes. One peculiar consequence was that it was possible to overdub additional sound onto a recording being played back. The recording was heavily worn by each playing, and it was nearly impossible to accurately remount a recorded foil after it had been removed from the cylinder. In this form, the only practical use that could be found for the phonograph was as a startling novelty for private amusement at home or public exhibitions for profit.

Edison's early patents show that he was aware that sound could be recorded as a spiral on a disc, but Edison concentrated his efforts on cylinders, since the groove on the outside of a rotating cylinder provides a constant velocity to the stylus in the groove, which Edison considered more "scientifically correct".

Edison's patent specified that the audio recording be embossed, and it was not until 1886 that vertically modulated incised recording using wax-coated cylinders was patented by Chichester Bell and Charles Sumner Tainter. They named their version the Graphophone.

Introduction of the disc record

The use of a flat recording surface instead of a cylindrical one was an obvious alternative which thought-experimenter Charles Cros initially favored and which practical experimenter Thomas Edison and others actually tested in the late 1870s and early 1880s. The oldest surviving example is a copper electrotype of a recording cut into a wax disc in 1881.

Cylindrical Dictaphone records continued in use until the mid-20th century. The commercialization of sound recording technology had been initially aimed at use in business correspondence, i.e. transcription into writing, in which the cylindrical form offered certain advantages. With paper documents being the end product, the cylinders were considered ephemeral; need to archive large numbers of bulky, fragile sound recordings seemed unlikely, and the ease of producing multiple copies was not a consideration.

In 1887, Emile Berliner patented a variant of the phonograph which he named the Gramophone. Berliner's approach was essentially the same one proposed, but never implemented, by Charles Cros in 1877. The diaphragm was linked to the recording stylus in a way that caused it to vibrate laterally (side to side) as it traced a spiral onto a zinc disc very thinly coated with a compound of beeswax. The zinc disc was then immersed in a bath of chromic acid; this etched a groove into the disc where the stylus had removed the coating, after which the recording could be played. With some later improvements the flat discs of Berliner could be produced in large quantities at much lower cost than the cylinders of Edison's system.

In May 1889, in San Francisco, the first "phonograph parlor" opened. It featured a row of coin-operated machines, each supplied with a different wax cylinder record. The customer selected a machine according to the title that it advertised, inserted a nickel, then heard the recording through stethoscope-like listening tubes. By the mid-1890s, most American cities had at least one phonograph parlor. The coin-operated mechanism was invented by Louis T. Glass and William S. Arnold. The cabinet contained an Edison Class M or Class E phonograph. The Class M was powered by a wet-cell glass battery that would spill dangerous acid if it tipped over or broke. The Class E sold for a lower price and ran on 120 V DC. The phenomenon of phonograph parlors peaked in Paris around 1900: in Pathé's luxurious salon, patrons sat in plush upholstered chairs and chose from among many hundreds of available cylinders by using speaking tubes to communicate with attendants on the floor below.

By 1890, record manufacturers had begun using a rudimentary duplication process to mass-produce their product. While the live performers recorded the master phonograph, up to ten tubes led to blank cylinders in other phonographs. Until this development, each record had to be custom-made. Before long, a more advanced pantograph-based process made it possible to simultaneously produce 90-150 copies of each record. However, as demand for certain records grew, popular artists still needed to re-record and re-re-record their songs. Reportedly, the medium's first major African-American star George Washington Johnson was obliged to perform his "The Laughing Song" (or the separate "The Whistling Coon") literally thousands of times in a studio during his recording career. Sometimes he would sing "The Laughing Song" more than fifty times in a day, at twenty cents per rendition. (The average price of a single cylinder in the mid-1890s was about fifty cents.)

Oldest surviving recordings

Lambert's lead cylinder recording for an experimental talking clock is often identified as the oldest surviving playable sound recording, although the evidence advanced for its early date is controversial. Wax phonograph cylinder recordings of Handel's choral music made on June 29, 1888, at The Crystal Palace in London were thought to be the oldest-known surviving musical recordings, until the recent playback by a group of American historians of a phonautograph recording of Au clair de la lune made on April 9, 1860. The 1860 phonautogram had not until then been played, as it was only a transcription of sound waves into graphic form on paper for visual study. Recently developed optical scanning and image processing techniques have given new life to early recordings by making it possible to play unusually delicate or physically unplayable media without physical contact.

A recording made on a sheet of tinfoil at an 1878 demonstration of Edison's phonograph in St. Louis, Missouri has been played back by optical scanning and digital analysis. A few other early tinfoil recordings are known to survive, including a slightly earlier one which is believed to preserve the voice of U.S. President Rutherford B. Hayes, but as of May 2014 they have not yet been scanned. These antique tinfoil recordings, which have typically been stored folded, are too fragile to be played back with a stylus without seriously damaging them. Edison's 1877 tinfoil recording of Mary Had a Little Lamb, not preserved, has been called the first instance of recorded verse. On the occasion of the 50th anniversary of the phonograph, Edison recounted reciting Mary Had a Little Lamb to test his first machine. The 1927 event was filmed by an early sound-on-film newsreel camera, and an audio clip from that film's soundtrack is sometimes mistakenly presented as the original 1877 recording. Wax cylinder recordings made by 19th century media legends such as P. T. Barnum and Shakespearean actor Edwin Booth are amongst the earliest verified recordings by the famous that have survived to the present.

Improvements at the Volta Laboratory

Volta's early challenge

Meanwhile, Bell, a scientist and experimenter at heart, was looking for new worlds to conquer after his invention of the telephone. According to Sumner Tainter, it was through Gardiner Green Hubbard that Bell took up the phonograph challenge. Bell had married Hubbard's daughter Mabel in 1879 while Hubbard was president of the Edison Speaking Phonograph Co., and his organization, which had purchased the Edison patent, was financially troubled because people did not want to buy a machine which seldom worked well and proved difficult for the average person to operate.

In 1879 Hubbard got Bell interested in improving the phonograph, and it was agreed that a laboratory should be set up in Washington. Experiments were also to be conducted on the transmission of sound by light, which resulted in the selenium-celled Photophone.

Volta Graphophone

By 1881, the Volta associates had succeeded in improving an Edison tinfoil machine to some extent. Wax was put in the grooves of the heavy iron cylinder, and no tinfoil was used. Rather than apply for a patent at that time, however, they deposited the machine in a sealed box at the Smithsonian, and specified that it was not to be opened without the consent of two of the three men.

The sound vibrations had been indented in the wax which had been applied to the Edison phonograph. The following was the text of one of their recordings: "There are more things in heaven and earth, Horatio, than are dreamed of in your philosophy. I am a Graphophone and my mother was a phonograph." Most of the disc machines designed at the Volta Lab had their disc mounted on vertical turntables. The explanation is that in the early experiments, the turntable, with disc, was mounted on the shop lathe, along with the recording and reproducing heads. Later, when the complete models were built, most of them featured vertical turntables.

One interesting exception was a horizontal seven inch turntable. The machine, although made in 1886, was a duplicate of one made earlier but taken to Europe by Chichester Bell. Tainter was granted U.S. Patent 385,886 on July 10, 1888. The playing arm is rigid, except for a pivoted vertical motion of 90 degrees to allow removal of the record or a return to starting position. While recording or playing, the record not only rotated, but moved laterally under the stylus, which thus described a spiral, recording 150 grooves to the inch.

The preserved Bell and Tainter records are of both the lateral cut and the Edison-style hill-and-dale (up-and-down) styles. Edison for many years used the "hill-and-dale" method on both his cylinders and Diamond Disc records, and Emile Berliner is credited with the invention of the lateral cut, acid-etched Gramophone record in 1887. The Volta associates, however, had been experimenting with both formats and directions of groove modulation as early as 1881.

The basic distinction between the Edison's first phonograph patent and the Bell and Tainter patent of 1886 was the method of recording. Edison's method was to indent the sound waves on a piece of tin foil, while Bell and Tainter's invention called for cutting, or "engraving", the sound waves into a wax record with a sharp recording stylus.

Graphophone commercialization

In 1885, when the Volta Associates were sure that they had a number of practical inventions, they filed patent applications and began to seek out investors. The Volta Graphophone Company of Alexandria, Virginia, was created on January 6, 1886 and incorporated on February 3, 1886. It was formed to control the patents and to handle the commercial development of their sound recording and reproduction inventions, one of which became the first Dictaphone.

After the Volta Associates gave several demonstrations in the City of Washington, businessmen from Philadelphia created the American Graphophone Company on March 28, 1887, in order to produce and sell the machines for the budding phonograph marketplace. The Volta Graphophone Company then merged with American Graphophone, which itself later evolved into Columbia Records.

Shortly after American Graphophone's creation, Jesse H. Lippincott used nearly $1 million of an inheritance to gain control of it, as well as the rights to the Graphophone and the Bell and Tainter patents. Not long later Lippincott purchased the Edison Speaking Phonograph Company. He then created the North American Phonograph Company to consolidate the national sales rights of both the Graphophone and the Edison Speaking Phonograph. In the early 1890s Lippincott fell victim to the unit's mechanical problems and also to resistance from stenographers.

A coin-operated version of the Graphophone, U.S. Patent 506,348, was developed by Tainter in 1893 to compete with nickel-in-the-slot entertainment phonograph U.S. Patent 428,750 demonstrated in 1889 by Louis T. Glass, manager of the Pacific Phonograph Company.

Disc vs. cylinder as a recording medium

Discs are not inherently better than cylinders at providing audio fidelity. Rather, the advantages of the format are seen in the manufacturing process: discs can be stamped; cylinders could not be until 1901-1902 when the gold moulding process was introduced by Edison.

Recordings made on a cylinder remain at a constant linear velocity for the entirety of the recording, while those made on a disc have a higher linear velocity at the outer portion of the disc compared to the inner portion.

Edison's patented recording method recorded with vertical modulations in a groove. Berliner utilized a laterally modulated groove.

Though Edison's recording technology was better than Berliner's, there were commercial advantages to a disc system since the disc could be easily mass-produced by molding and stamping and it required less storage space for a collection of recordings.

Berliner successfully argued that his technology was different enough from Edison's that he did not need to pay royalties on it, which reduced his business expenses.

Through experimentation, in 1892 Berliner began commercial production of his disc records, and "gramophones". His " gramophone record" was the first disc record to be offered to the public. They were five inches (12.7 cm) in diameter and recorded on one side only. Seven-inch (17.5 cm) records followed in 1895. Also in 1895 Berliner replaced the hard rubber used to make the discs with a shellac compound. Berliner's early records had very poor sound quality, however. Work by Eldridge R. Johnson eventually improved the sound fidelity to a point where it was as good as the cylinder. By late 1901, ten-inch (25 cm) records were marketed by Johnson and Berliner's Victor Talking Machine Company, and Berliner had sold his interests. In 1904, discs were first pressed with music on both sides and capable of around seven minutes total playing time, as opposed to the cylinder's typical duration on two minutes at that time. As a result of this and the fragility of wax cylinders in transit and storage, cylinders sales declined. Edison felt the increasing commercial pressure for disc records, and by 1912, though reluctant at first, his production of disc records was in full swing. This was the Edison Disc Record. Nevertheless, he continued to manufacture cylinders until 1929 and was last to withdraw from that market.

From the mid-1890s until World War I, both phonograph cylinder and disc recordings and machines to play them on were widely mass-marketed and sold. The disc system superseded the cylinder in Europe by 1906 when both Columbia and Pathe withdrew from that market. By 1913, Edison was the only company still producing cylinders in the USA although in Great Britain small manufacturers pressed on until 1922.

Dominance of the disc record

Berliner's lateral disc record was the ancestor of the 78 rpm, 45 rpm, 33⅓ rpm, and all other analogue disc records popular for use in sound recording. See gramophone record.

The 1920s brought improved radio technology. Radio sales increased, bringing many phonograph dealers to near financial ruin. With efforts at improved audio fidelity, the big record companies succeeded in keeping business booming through the end of the decade, but the record sales plummeted during the Great Depression, with many companies merging or going out of business.

Record sales picked up appreciably by the late 30s and early 40s, with greater improvements in fidelity and more money to be spent. By this time home phonographs had become much more common, though it wasn't until the 1940s that console radio/phono set-ups with automatic record changers became more common.

Booms in record sales returned after the Second World War, as industry standards changed from 78s to vinyl, long-playing records (commonly called record albums), which could contain an entire symphony, and 45s which usually contained one hit song popularized on the radio - thus the term "single" record - plus another song on the back or "flip" side. An " extended play" version of the 45 was also available, designated 45 EP, which provided capacity for longer musical selections, or for two regular-length songs per side.

Shortcomings include surface noise caused by dirt or abrasions (scratches) and failure caused by deep surface scratches causing skipping of the stylus forward and missing a section, or groove lock, causing a section to repeat, usually punctuated by a popping noise. This was so common that the phrase: "you sound like a broken record," was coined, referring to someone who is being annoyingly repetitious.

First all-transistor phonograph

In 1955, Philco developed and produced the world's first all- transistor phonograph models TPA-1 and TPA-2, which were announced in the June 28, 1955 edition of the Wall Street Journal. Philco started to sell these all-transistor phonographs in the fall of 1955, for the price of $59.95. The October 1955 issue of Radio & Television News magazine (page 41), had a full page detailed article on Philco's new consumer product. The all-transistor portable phonograph TPA-1 and TPA-2 models played only 45rpm records and used four 1.5 volt "D" batteries for their power supply. The "TPA" stands for "Transistor Phonograph Amplifier". Their circuitry used three Philco germanium PNP alloy-fused junction audio frequency transistors. After the 1956 season had ended, Philco decided to discontinue both models, for transistors were too expensive compared to vacuum tubes, but by 1961 a $49.95 ($452.94 in 2021) portable, battery-powered radio-phonograph with seven transistors was available.

By the 1960s, cheaper portable record players and record changers which played stacks of records in wooden console cabinets were popular, usually with heavy and crude tonearms in the portables. The consoles were often equipped with better quality pick-up cartridges. Even pharmacies stocked 45 rpm records at their front counters. Rock music played on 45s became the soundtrack to the 1960s as people bought the same songs that were played free of charge on the radio. Some record players were even tried in automobiles, but were quickly displaced by 8-track and cassette tapes.

The fidelity of sound reproduction made great advances during the 1970s, as turntables became very precise instruments with belt or direct drive, jewel-balanced tonearms, some with electronically controlled linear tracking and magnetic cartridges. Some cartridges had frequency response above 30 kHz for use with CD-4 quadraphonic 4 channel sound. A high fidelity component system which cost well under $1,000 could do a very good job of reproducing very accurate frequency response across the human audible spectrum from 20 Hz to 20,000 Hz with a $200 turntable which would typically have less than 0.05% wow and flutter and very low rumble (low frequency noise). A well-maintained record would have very little surface noise.

A novelty variation on the standard format was the use of multiple concentric spirals with different recordings. Thus when the record was played multiple times, different recordings would play, seemingly at random. These were often utilized in talking toys and games.

By the turn of the 21st century, the turntable had become a niche product, as the price of CD players, which reproduce music free of pops and scratches, fell far lower than high-fidelity tape players or turntables. Nevertheless, there is some increase in interest; many big-box media stores carry turntables, as do professional DJ equipment stores. Most low-end and mid-range amplifiers omit the phono input; but on the other hand, low-end turntables with built-in phono pre-amplifiers are widely available. Some combination systems include a basic turntable, a CD player, a cassette deck. and a radio, in a retro-styled cabinet. Records also continue to be manufactured and sold today, albeit in smaller quantities than in the disc phonograph's heyday.

Turntable technology

Turntable construction

Inexpensive record players typically used a flanged steel stamping for the turntable structure. A rubber disc would be secured to the top of the stamping to provide traction for the record, as well as a small amount of vibration isolation. The spindle bearing usually consisted of a bronze bushing. The flange on the stamping provided a convenient place to drive the turntable by means of an idler wheel (see below). While light and cheap to manufacture, these mechanisms had low inertia, making motor speed instabilities more pronounced.

Costlier turntables made from heavy aluminium castings have greater balanced mass and inertia, helping minimize vibration at the stylus, and maintaining constant speed without wow or flutter, even if the motor exhibits cogging effects. Like stamped steel turntables, they were topped with rubber. Because of the increased mass, they usually employed ball bearings or roller bearings in the spindle to reduce friction and noise. Most are belt or direct drive, but some use an idler wheel. A specific case was the Swiss "Lenco" drive, which possessed a very heavy turntable coupled via an idler wheel to a long, tapered motor drive shaft. This enabled stepless rotation or speed control on the drive. Because of this feature the Lenco became popular in the late 1950s with dancing schools, because the dancing instructor could lead the dancing exercises at different speeds.

By the early 1980s, some companies started producing very inexpensive turntables that displaced the products of companies like BSR. Commonly found in "all-in-one" stereos from assorted far-east manufacturers, they used a thin plastic table set in a plastic plinth, no mats, belt drive, weak motors, and often, lightweight plastic tonearms with no counterweight. Most used sapphire pickups housed in ceramic cartridges, and they lacked several features of earlier units, such as auto-start and record-stacking. While not as common now that turntables are absent from the cheap "all-in-one" units, this type of turntable has made a strong resurgence in nostalgia-marketed record players.

Turntable drive systems

From the earliest phonograph designs, many of which were powered by spring-wound mechanisms, a speed governor was essential. Most of these employed some type of flywheel-friction disc to control the speed of the rotating cylinder or turntable; as the speed increased, centrifugal force caused a brake-often a felt pad-to rub against a smooth metal surface, slowing rotation. Electrically powered turntables, whose rotational speed was governed by other means, eventually made their mechanical counterparts obsolete. The mechanical governor was, however, still employed in some toy phonographs (such as those found in talking dolls) until they were replaced by digital sound generators in the late 20th century.

Many modern players have platters with a continuous series of strobe markings machined or printed around their edge. Viewing these markings in artificial light at mains frequency produces a stroboscopic effect, which can be used to verify proper rotational speed. Additionally, the edge of the turntable can contain magnetic markings to provide feedback pulses to an electronic speed-control system.

Idler-wheel drive system

Until the 1970s, the idler-wheel drive was the most common on turntables, except for higher-end audiophile models. However, even some higher-end turntables, such as the Lenco, Garrard, EMT, and Dual turntables, used idler-wheel drive.

Belt drive system

Belt drives brought improved motor and platter isolation compared to idler-wheel designs. Motor noise, generally heard as low-frequency rumble, is greatly reduced. The design of the belt drive turntable allows for a less expensive motor than the direct-drive turntable to be used. The elastomeric belt absorbs motor vibrations and noise which could otherwise be picked up by the stylus. It also absorbs small, fast speed variations, caused by "cogging", which in other designs are heard as "flutter."

The "Acoustical professional" turntable (earlier marketed under Dutch "Jobo prof") of the 1960s however possessed an expensive German drive motor, the "Pabst Aussenläufer" ("Pabst outrunner"). As this motor name implied, the rotor was on the outside of the motor and acted as a flywheel ahead of the belt-driven turntable itself. In combination with a steel to nylon turntable bearing (with molybdenum disulfide inside for lifelong lubrication) very low wow, flutter and rumble figures were achieved.

Direct drive system

Direct-drive turntables drive the platter directly without utilizing intermediate wheels, belts, or gears as part of a drive train. This requires good engineering, with advanced electronics for acceleration and speed control. Matsushita's Technics division introduced the first commercially successful direct drive platter, model SP10, in 1969, which was joined by the Technics SL-1200 turntable, in 1972. Its updated model, SL-1200MK2, released in 1978, had a stronger motor, a convenient pitch control slider for beatmatching and a stylus illuminator, which made it the long-standing favourite among disc jockeys ( see "Turntablism"). By the beginnings of the 80s, lowering of costs in microcontroller electronics made direct drive turntables more affordable.

Audiophile grade turntables start at a few hundred dollars and range upwards of $100,000, depending on the complexity and quality of design and manufacture. The common view is that there are diminishing returns with an increase in price - a turntable costing $1,000 would not sound significantly better than a turntable costing $500; nevertheless, there exists a large choice of expensive turntables.

Arm systems

The tone arm (or tonearm) holds the pickup cartridge over the groove, the stylus tracking the groove with the desired force to give the optimal compromise between good tracking and minimizing wear of the stylus and record groove. At its simplest, a tone arm is a pivoted lever, free to move in two axes (vertical and horizontal) with a counterbalance to maintain tracking pressure.

However, the requirements of high-fidelity reproduction place more demands upon the arm design. In a perfect world:

The tone arm must track the groove without distorting the stylus assembly, so an ideal arm would have no mass, and frictionless bearings, requiring zero force to move it.

The arm should not oscillate following a displacement, so it should either be both light and very stiff, or suitably damped.

The arm must not resonate with vibrations induced by the stylus or from the turntable motor or plinth, so it must be heavy enough to be immune to those vibrations, or it must be damped to absorb them.

The arm should keep the cartridge stylus tangent to the groove it's in as it moves across the record, with minimal variation in angle.

These demands are contradictory and impossible to realize (massless arms and zero-friction bearings do not exist in the real world), so tone arm designs require engineering compromises. Solutions vary, but all modern tonearms are at least relatively lightweight and stiff constructions, with precision, very low friction pivot bearings in both the vertical and horizontal axes. Most arms are made from some kind of alloy (the cheapest being aluminium), but some manufacturers use balsa wood, while others use carbon fiber or graphite. The latter materials favor a straight arm design; alloys' properties lend themselves to S-type arms.

The tone arm got its name before the age of electronics. It originally served to conduct actual sound waves from a purely mechanical "pickup" called a sound box or reproducer to a so-described "amplifying" horn. The earliest electronic record players, introduced at the end of 1925, had massive electromagnetic pickups that contained a horseshoe magnet, used disposable steel needles, and weighed several ounces. Their full weight rested on the record, providing ample tracking force to overcome their low compliance but causing rapid record wear. The tone arms were rudimentary and remained so even after lighter crystal pickups appeared about ten years later. When fine-grooved vinyl records were introduced in the late 1940s, still smaller and lighter crystal (later, ceramic) cartridges with semi-permanent jewel styluses became standard. In the mid-1950s these were joined by a new generation of magnetic cartridges that bore little resemblance to their crude ancestors. Far smaller tracking forces became possible and the balanced arm came into use.

Prices varied widely. The well-known and extremely popular high-end S-type SME arm of the 1970-1980 era not only had a complicated design, it was also very costly. On the other hand, even some cheaper arms could be of professional quality: the "All Balance" arm, made by the now-defunct Dutch company Acoustical, was only €30 [equivalent]. It was used during that period by all official radio stations in the Dutch Broadcast studio facilities of the NOS, as well as by the pirate radio station Veronica. Playing records from a boat in international waters, the arm had to withstand sudden ship movements. Anecdotes indicate this low-cost arm was the only one capable of keeping the needle firmly in the groove during heavy storms at sea.

Quality arms employ an adjustable counterweight to offset the mass of the arm and various cartridges and headshells. On this counterweight, a calibrated dial enables easy adjustment of stylus force. After perfectly balancing the arm, the dial itself is "zeroed"; the stylus force can then be dialed in by screwing the counterweight towards the fulcrum. (Sometimes a separate spring or smaller weight provides fine tuning.) Stylus forces of 10 to 20 mN (1 to 2 grams-force) are typical for modern consumer turntables, while forces of up to 50 mN (5 grams) are common for the tougher environmental demands of party deejaying or turntablism. Of special adjustment consideration, Stanton cartridges of the 681EE(E) series [and others like them] feature a small record brush ahead of the cartridge. The upforce of this brush, and its added drag require compensation of both tracking force (add 1 gram) and anti-skating adjustment values (see next paragraph for description).

Even on a perfectly flat LP, tonearms are prone to two types of tracking errors that affect the sound. As the tonearm tracks the groove, the stylus exerts a frictional force tangent to the arc of the groove, and since this force does not intersect the tone arm pivot, a clockwise rotational force (moment) occurs and a reaction skating force is exerted on the stylus by the record groove wall away from center of the disc. Modern arms provide an anti-skate mechanism, using springs, hanging weights, or magnets to produce an offsetting counter-clockwise force at the pivot, making the net lateral force on the groove walls near zero. The second error occurs as the arm sweeps in an arc across the disc, causing the angle between the cartridge head and groove to change slightly. A change in angle, albeit small, will have a detrimental effect (especially with stereo recordings) by creating different forces on the two groove walls, as well as a slight timing shift between left/right channels. Making the arm longer to reduce this angle is a partial solution, but less than ideal. A longer arm weighs more, and only an infinitely long [pivoted] arm would reduce the error to zero. Some designs (Burne-Jones, and Garrard "Zero" series) use dual arms in a parallelogram arrangement, pivoting the cartridge head to maintain a constant angle as it moves across the record. Unfortunately this "solution" creates more problems than it solves, compromising rigidity and creating sources of unwanted noise.

The pivoted arm produces yet another problem which is unlikely to be significant to the audiophile, though. As the master was originally cut in a linear motion from the edge towards the center, but the stylus on the pivoted arm always draws an arc, this causes a timing drift that is most significant when digitizing music and beat mapping the data for synchronization with other songs in a DAW or DJ software unless the software allows building a non-linear beat map. As the contact point of the stylus on the record wanders farther from the linear path between the starting point and center hole, the tempo and pitch tend to decrease towards the middle of the record, until the arc reaches its apex. After that the tempo and pitch increase towards the end as the contact point comes closer to the linear path again. Because the surface speed of the record is lower at the end, the relative speed error from the same absolute distance error is higher at the end, and the increase in tempo is more notable towards the end than the decrease towards the middle. This can be somewhat reduced by a curved arm pivoted so that the end point of the arc stays farther from the linear path than the starting point, or by a long straight arm that pivots perpendicularly to the linear path in the middle of the record. However the tempo droop at the middle can only be completely avoided by a linear tracking arm.

Linear tracking

If the arm is not pivoted, but instead carries the stylus along a radius of the disc, there is no skating force and little to no cartridge angle error. Such arms are known as linear tracking or tangential arms. These are driven along a track by various means, from strings and pulleys, to worm gears or electromagnets. The cartridge's position is usually regulated by an electronic servomechanism or mechanical interface, moving the stylus properly over the groove as the record plays, or for song selection.

There are long-armed and short-armed linear arm designs. On a perfectly flat record a short arm will do, but once the record is even slightly warped, a short arm will be troublesome. Any vertical motion of the record surface at the stylus contact point will cause the stylus to considerably move longitudinally in the groove. This will cause the stylus to ride non-tangentially in the groove and cause a stereo phase error as well as pitch error every time the stylus rides over the warp. Also the arm track can come into touch with the record. A long arm will not completely eliminate this problem but will tolerate warped records much better.

Early developments in linear turntables were from Rek-O-Kut (portable lathe/phonograph) and Ortho-Sonic in the 1950s, and Acoustical in the early 1960s. These were eclipsed by more successful implementations of the concept from the late 1960s through the early 1980s. Of note are Rabco's SL-8, followed by Bang & Olufsen with its Beogram 4000 model in 1972. These models positioned the track outside the platter's edge, as did turntables by Harman Kardon, Mitsubishi, Pioneer, Yamaha, Sony, etc. A 1970s design from Revox harkened back to the 1950s attempts (and, record lathes), positioning the track directly over the record. An enclosed bridge-like assembly is swung into place from the platter's right edge to its middle. Once in place, a short tonearm under this "bridge" plays the record, driven across laterally by a motor. The Sony PS-F5/F9 (1983) uses a similar, miniaturized design, and can operate in a vertical or horizontal orientation. The Technics SL-10, introduced in 1981, was the first direct drive linear tracking turntable, and placed the track and arm on the underside of the rear-hinged dust cover, to fold down over the record, similar to the SL-Q6 pictured.

The earliest Edison phonographs used horizontal, spring-powered drives to carry the stylus across the recording at a pre-determined rate. But, historically as a whole, the linear tracking systems never gained wide acceptance, due largely to their complexity and associated production/development costs. The resources it takes to produce one incredible linear turntable could produce several excellent ones. Some of the most sophisticated and expensive tonearms and turntable units ever made are linear trackers, from companies such as Rockport and Clearaudio. In theory, it seems nearly ideal; a stylus replicating the motion of the recording lathe used to cut the "master" record could result in minimal wear and maximum sound reproduction. In practice, in vinyl's heyday it was generally too much too late.

Since the early 1980s, an elegant solution has been the near-frictionless air bearing linear arm that requires no tracking drive mechanism other than the record groove. This provides a similar benefit as the electronic linear tonearm without the complexity and necessity of servo-motor correction for tracking error. In this case the trade-off is the introduction of pneumatics in the form of audible pumps and tubing. A more elegant solution is the mechanically driven low-friction design, also driven by the groove. Examples include Souther Engineering (U.S.A.), Clearaudio (Germany), and Aura (Czech Republic). This design places an exceeding demand upon precision engineering due to the lack of pneumatics.

Pickup systems

Historically, most high-fidelity "component" systems (preamplifiers or receivers) that accepted input from a phonograph turntable had separate inputs for both ceramic and magnetic cartridges (typically labeled "CER" and "MAG"). One piece systems often had no additional phono inputs at all, regardless of type.

Most systems today, if they accept input from a turntable at all, are configured for use only with magnetic cartridges. Manufacturers of high-end systems often have in-built moving coil amplifier circuitry, or outboard head-amplifiers supporting either moving magnet or moving coil cartridges that can be plugged into the line stage.

Additionally, cartridges may contain styli or needles that can be separated according to their tip: Spherical styli, and elliptical styli. Spherical styli have their tip shaped like one half of a sphere, and elliptical styli have their tip shaped like one end of an ellipse. Spherical styli preserve more of the groove of the record than elliptical styli, while elliptical styli offer higher sound quality.

Piezoelectric (crystal/ceramic) cartridges

Early electronic phonographs used a piezo-electric for pickup (though the earliest electronic phonographs used crude magnetic pick-ups), where the mechanical movement of the stylus in the groove generates a proportional electrical voltage by creating stress within a crystal (typically Rochelle salt). Crystal pickups are relatively robust, and produce a substantial signal level which requires only a modest amount of further amplification. The output is not very linear however, introducing unwanted distortion. It is difficult to make a crystal pickup suitable for quality stereo reproduction, as the stiff coupling between the crystal and the long stylus prevents close tracking of the needle to the groove modulations. This tends to increase wear on the record, and introduces more distortion. Another problem is the hygroscopic nature of the crystal itself: it absorbs moisture from the air and may dissolve. The crystal was protected by embedding it in other materials, without hindering the movement of the pickup mechanism itself. After a number of years, the protective jelly often deteriorated or leaked from the cartridge case and the full unit needed replacement.

The next development was the ceramic cartridge, a piezoelectric device that used newer and better materials. These were more sensitive, and offered greater compliance, that is, lack of resistance to movement and so increased ability to follow the undulations of the groove without gross distorting or jumping out of the groove. Higher compliance meant lower tracking forces and reduced wear to both the disc and stylus. It also allowed ceramic stereo cartridges to be made.

Between the 1950s and 1970s, ceramic cartridges became common in low-quality phonographs, but better high-fidelity (or "hi-fi") systems used magnetic cartridges. The availability of low-cost magnetic cartridges from the 1970s onwards made ceramic cartridges obsolete for essentially all purposes. At the seeming end of the market lifespan of ceramic cartridges, someone accidentally discovered that by terminating a specific ceramic mono cartridge (the Ronette TX88) not with the prescribed 47 kΩ resistance, but with approx. 10 kΩ, it could be connected to the moving magnet (MM) input too. The result, a much smoother frequency curve extended the lifetime for this popular and very cheap type.

Magnetic cartridges

There are two common designs for magnetic cartridges, moving magnet (MM) and moving coil (MC) (originally called dynamic). Both operate on the same physics principle of electromagnetic induction. The moving magnet type was by far the most common and more robust of the two, though audiophiles often claim that the moving coil system yields higher fidelity sound.

In either type, the stylus itself, usually of diamond, is mounted on a tiny metal strut called a cantilever, which is suspended using a collar of highly compliant plastic. This gives the stylus the freedom to move in any direction. On the other end of the cantilever is mounted a tiny permanent magnet (moving magnet type) or a set of tiny wound coils (moving coil type). The magnet is close to a set of fixed pick-up coils, or the moving coils are held within a magnetic field generated by fixed permanent magnets. In either case, the movement of the stylus as it tracks the grooves of a record causes a fluctuating magnetic field, which causes a small electric current to be induced in the coils. This current closely follows the sound waveform cut into the record, and may be transmitted by wires to an electronic amplifier where it is processed and amplified in order to drive a loudspeaker. Depending upon the amplifier design, a phono-preamplifier may be necessary.

In most moving magnet designs, the stylus itself is detachable from the rest of the cartridge so it can easily be replaced. There are three primary types of cartridge mounts. The most common type is attached using two small screws to a headshell that then plugs into the tonearm, while another is a standardized "P-mount" or "T4P" cartridge (invented by Technics in 1980 and adopted by other manufacturers) that plugs directly into the tonearm. Many P-mount cartridges come with adapters to allow them to be mounted to a headshell. The third type is used mainly in cartridges designed for DJ use and it has a standard round headshell connector. Some mass market turntables use a proprietary integrated cartridge that cannot be upgraded.

An alternative design is the moving iron variation on moving magnet used by ADC, Grado, Stanton/Pickering 681 series, Ortofon OM and VMS series, and the MMC cartridge of Bang & Olufsen. In these units, the magnet itself sits behind the four coils and magnetises the cores of all four coils. The moving iron cross at the other end of the coils varies the gaps between itself and each of these cores, according to its movements. These variations lead to voltage variations as described above.

Famous brands for magnetic cartridges are: Grado, Stanton/Pickering (681EE/EEE), B&O (MM types for its two, non-compatible generations of parallel arm design), Shure (V15 Type I to V), Audio-Technica, Nagaoka, Dynavector, Koetsu, Ortofon, Technics, Denon and ADC.

Strain gauge cartridges

Strain gauge or "semiconductor" cartridges do not generate a voltage, but act like a variable resistor, whose resistance directly depends on the movement of the stylus. Thus, the cartridge "modulates" an external voltage supplied by the (special) preamplifier. These pickups were marketed by Euphonics, Sao Win, and Panasonic/Technics, amongst others.

The main advantages (compared to magnetic carts are):

The electrical connection from the cartridge to the preamplifier is immune to cable capacitance issues.

Being non-magnetic, the cartridge is immune to "hum" induced by stray magnetic fields (same advantage shared with ceramic cartridges).

The combination of electrical and mechanical advantages, plus the absence of magnetic yoke high-frequency losses, make them especially suitable to reproducing frequencies up to 50 kHz. Technics (Matsushita Electric) marketed a line of strain-gauge (labeled "semiconductor") cartridges especially intended for Compatible Discrete 4 quadraphonic records, requiring such high frequency response. Bass response down to 0 Hz is possible.

By using a suitable mechanical arrangement, VTA (vertical tracking angle) stays steady independent of the stylus vertical movements, with the consequent reduction in related distortions.

Being a force sensor, the strain-gauge cartridge can also measure the actual VTF (vertical tracking force) while in use.

The main disadvantage is the need of a special preamplifier that supplies a steady current (typically 5mA) to the semiconductor elements and handles a special equalization than the one needed for magnetic cartridges.

A high-end strain-gauge cartridge is currently sold by an audiophile company, with special preamplifiers available.

Electrostatic cartridges

Electrostatic cartridges were marketed by Stax in the 1950 and 1960 years. They needed individual operating electronics or preamplifiers.

Optical readout

A few specialist laser turntables read the groove optically using a laser pickup. Since there is no physical contact with the record, no wear is incurred. However, this "no wear" advantage is debatable, since vinyl records have been tested to withstand even 1200 plays with no significant audio degradation, provided that it is played with a high quality cartridge and that the surfaces are clean.

An alternative approach is to take a high-resolution photograph or scan of each side of the record and interpret the image of the grooves using computer software. An amateur attempt using a flatbed scanner lacked satisfactory fidelity. A professional system employed by the Library of Congress produces excellent quality.

A smooth-tipped stylus (in popular usage often called a needle due to the former use of steel needles for the purpose) is used to play the recorded groove. A special chisel-like stylus is used to engrave the groove into the master record.

The stylus is subject to hard wear as it is the only small part that comes into direct contact with the spinning record. In terms of the pressure imposed on its minute areas of actual contact, the forces it must bear are enormous. There are three desired qualities in a stylus: first, that it faithfully follows the contours of the recorded groove and transmits its vibrations to the next part in the chain; second, that it does not damage the recorded disc; and third, that it is resistant to wear. A worn-out, damaged or defective stylus tip will degrade audio quality and injure the groove.

Different materials for the stylus have been used over time. Thomas Edison introduced the use of sapphire in 1892 and the use of diamond in 1910 for his cylinder phonographs. The Edison Diamond Disc players (1912-1929), when properly played, hardly ever required the stylus to be changed. The styli for vinyl records were also made out of sapphire or diamond. A specific case is the specific stylus type of Bang & Olufsen's (B&O) moving magnet cartridge MMC 20CL, mostly used in parallel arm B&O turntables in the 4002/6000 series. It uses a sapphire stem on which a diamond tip is fixed by a special adhesive. A stylus tip mass as low as 0.3 milligram is the result and full tracking only requires 1 gram of stylus force, reducing record wear even further. Maximum distortion (2nd harmonic) fell below 0.6%.

Other than the Edison and European Pathé disc machines, early disc players, both external horn and internal horn "Victrola" style models, normally used very short-lived disposable needles. The most common material was steel, although other materials such as copper, tungsten, bamboo and cactus were used. Steel needles needed to be replaced frequently, preferably after each use, due to their very rapid wear from bearing down heavily on the mildly abrasive shellac record. Rapid wear was an essential feature so that their imprecisely formed tips would be quickly worn into compliance with the groove's contours. Advertisements implored customers to replace their steel needles after each record side. Steel needles were inexpensive, e.g., a box of 500 for 50 US cents, and were widely sold in packets and small tins. They were available in different thicknesses and lengths. Thick, short needles produced strong, loud tones while thinner, longer needles produces softer, muted tones. In 1916, in the face of a wartime steel shortage, Victor introduced their "Tungs-Tone" brand extra-long-playing needle, which was advertised to play between 100 and 300 records. It consisted of a brass shank into which a very hard and strong tungsten wire, somewhat narrower than the standard record groove, had been fitted. The protruding wire wore down, but not out, until it was worn too short to use. Later in the 78 rpm era, hardened steel and chrome-plated needles came on the market, some of which were claimed to play 10 to 20 record sides each.

When sapphires were introduced for the 78 rpm disc and the LP, they were made by tapering a stem and polishing the tip to a sphere with a radius of around 70 and 25 micrometers respectively. A sphere is not equal to the form of the cutting stylus and by the time diamond needles came to the market, a whole discussion was started on the effect of circular forms moving through a non-circular cut groove. It can be easily shown that vertical, so called "pinching" movements were a result and when stereophonic LPs were introduced, unwanted vertical modulation was recognized as a problem. Also, the needle started its life touching the groove on a very small surface, giving extra wear on the walls.

Another problem is in the tapering along a straight line, while the side of the groove is far from straight. Both problems were attacked together: by polishing the diamond in a certain way that it could be made doubly elliptic. 1) the side was made into one ellipse as seen from behind, meaning the groove touched along a short line and 2) the ellipse form was also polished as seen from above and curvature in the direction of the groove became much smaller than 25 micrometers e.g. 13 micrometers. With this approach a number of irregularities were eliminated. Furthermore, the angle of the stylus, which used to be always sloping backwards, was changed into the forward direction, in line with the slope the original cutting stylus possessed. These styli were expensive to produce, but the costs were effectively offset by their extended lifespans.

The next development in stylus form came about by the attention to the CD-4 quadraphonic sound modulation process, which requires up to 50 kHz frequency response, with cartridges like Technics EPC-100CMK4 capable of playback on frequencies up to 100 kHz. This requires a stylus with a narrow side radius, such as 5 µm (or 0.2 mil). A narrow-profile elliptical stylus is able to read the higher frequencies (greater than 20 kHz), but at an increased wear, since the contact surface is narrower. For overcoming this problem, the Shibata stylus was invented around 1972 in Japan by Norio Shibata of JVC, fitted as standard on quadraphonic cartridges, and marketed as an extra on some high-end cartridges.

The Shibata-designed stylus offers a greater contact surface with the groove, which in turn means less pressure over the vinyl surface and thus less wear. A positive side effect is that the greater contact surface also means the stylus will read sections of the vinyl that were not touched (or "worn") by the common spherical stylus. In a demonstration by JVC records "worn" after 500 plays at a relatively very high 4.5 gf tracking force with a spherical stylus, played "as new" with the Shibata profile.

Other advanced stylus shapes appeared following the same goal of increasing contact surface, improving on the Shibata. Chronologically: "Hughes" Shibata variant (1975), "Ogura" (1978), Van den Hul (1982). Such a stylus may be marketed as "Hyperelliptical" (Shure), "Alliptic", "Fine Line" (Ortofon), "Line contact" (Audio Technica), "Polyhedron", "LAC", or "Stereohedron" (Stanton).

A keel-shaped diamond stylus appeared as a byproduct of the invention of the CED Videodisc. This, together with laser-diamond-cutting technologies, made possible the "ridge" shaped stylus, such as the Namiki (1985) design, and Fritz Gyger (1989) design. This type of stylus is marketed as "MicroLine" (Audio technica), "Micro-Ridge" (Shure), or "Replicant" (Ortofon).

It is important to point out that most of those stylus profiles are still being manufactured and sold, together with the more common spherical and elliptical profiles. This is despite the fact that production of CD-4 quadraphonic records ended by the late 1970s.

Record materials

Early materials in the 19th century were hardened rubber, wax, and celluloid, but early in the 20th century a shellac compound became the standard. Since shellac is not hard enough to withstand the wear of steel needles on heavy tone arms, filler made of pulverized shale was added. Shellac was also fragile, and records often shattered or cracked. This was a problem for home records, but it became a bigger problem in the late 1920s with the Vitaphone sound-on-disc motion picture "talkie" system, developed in 1927.

To solve this problem, in 1930, RCA Victor made unbreakable records by mixing polyvinyl chloride with plasticisers, in a proprietary formula they called Victrolac, which was first used in 1931, in motion picture discs, and experimentally, in home records, the same year. However, with Sound-on-film achieving supremacy over sound-on-disc by 1931, the need for unbreakable records diminished and the production of vinyl home recordings was dropped as well, for the time being.

The Victrolac formula improved throughout the 1930s, and by the late 30s the material, by then called vinylite, was being used in records sent to radio stations for radio program records, radio commercials, and later, DJ copies of phonograph records, because vinyl records could be sent through the mail to radio stations without breaking. During WWII, there was a shortage of shellac, which had to be imported from Asia, and the U.S. government banned production of shellac records for the duration of the war. Vinylite was made domestically, though, and was being used for V-discs during the war. Record company engineers took a much closer look at the possibilities of vinyl, possibly that it might even replace shellac as the basic record material. After the war, RCA Victor and Columbia, by far the two leading records companies in America, perfected two new vinyl formats, which were both introduced in 1948, when the 33 RPM LP was introduced by Columbia and the 45 RPM single was introduced by RCA Victor. For a few years thereafter, however, 78 RPM records continued to be made in shellac until that format was phased out around 1958.

Equalization

Early "acoustical" record players used the stylus to vibrate a diaphragm that radiated the sound through a horn. Several serious problems resulted from this:

The maximum sound level achievable was quite limited, being limited to the physical amplification effects of the horn,

The energy needed to generate such sound levels as were obtainable had to come directly from the stylus tracing the groove. This required very high tracking forces that rapidly wore out both the stylus and the record on lateral cut 78 rpm records.

Because bass sounds have a higher amplitude than high frequency sounds (for the same perceived loudness), the space taken in the groove by low frequency sounds needed to be large (limiting playback time per side of the record) to accommodate the bass notes, yet the high frequencies required only tiny variations in the groove, which were easily affected by noise from irregularities (wear, contaminates, etc.) in the disc itself.

The introduction of electronic amplification allowed these issues to be addressed. Records are made with boosted high frequencies and reduced low frequencies, which allow for different ranges of sound to be produced. This reduces the effect of background noise, including clicks or pops, and also conserves the amount of physical space needed for each groove, by reducing the size of the low-frequency undulations.

During playback, the high frequencies must be rescaled to their original, flat frequency response-known as "equalization"-as well as being amplified. A phono input of an amplifier incorporates such equalization as well as amplification to suit the very low level output from a modern cartridge. Most hi-fi amplifiers made between the 1950s and the 1990s and virtually all DJ mixers are so equipped.

The widespread adoption of digital music formats, such as CD or satellite radio, has displaced phonograph records and resulted in phono inputs being omitted in most modern amplifiers. Some newer turntables include built-in preamplifiers to produce line-level outputs. Inexpensive and moderate performance discrete phono preamplifiers with RIAA equalization are available, while high-end audiophile units costing thousands of dollars continue to be available in very small numbers. Phono inputs are starting to reappear on amplifiers in the 2010s due to the vinyl revival.

Since the late 1950s, almost all phono input stages have used the RIAA equalization standard. Before settling on that standard, there were many different equalizations in use, including EMI, HMV, Columbia, Decca FFRR, NAB, Ortho, BBC transcription, etc. Recordings made using these other equalization schemes will typically sound odd if they are played through a RIAA-equalized preamplifier. High-performance (so-called "multicurve disc") preamplifiers, which include multiple, selectable equalizations, are no longer commonly available. However, some vintage preamplifiers, such as the LEAK varislope series, are still obtainable and can be refurbished. Newer preamplifiers like the Esoteric Sound Re-Equalizer or the K-A-B MK2 Vintage Signal Processor are also available. These kinds of adjustable phono equalizers are used by consumers wishing to play vintage record collections (often the only available recordings of musicians of the time) with the equalization used to make them.

In the 21st century

Turntables continue to be manufactured and sold in the 2010s, although in small numbers. While some audiophiles still prefer the sound of vinyl records over that of digital music sources (mainly compact discs), they represent a minority of listeners. As of 2015 the sale of vinyl LP's has increased 49-50% percent from the previous year although small in comparison to the sale of other formats which although more units were sold (Digital Sales, CDs) the more modern formats experienced a decline in sales. The quality of available record players, tonearms, and cartridges has continued to improve, despite diminishing demand, allowing turntables to remain competitive in the high-end audio market. Vinyl enthusiasts are often committed to the refurbishment and sometimes tweaking of vintage systems.

In 2017, vinyl LP sales were slightly decreased, at a rate of 5%, in comparison to previous years' numbers, regardless of the noticeable rise of vinyl records sales worldwide.

Updated versions of the 1970s era Technics SL-1200 (production ceased in 2010) have remained an industry standard for DJs to the present day. Turntables and vinyl records remain popular in mixing (mostly dance-oriented) forms of electronic music, where they allow great latitude for physical manipulation of the music by the DJ.

In hip hop music and occasionally in other genres, the turntable is used as a musical instrument by DJs, who use turntables along with a DJ mixer to create unique rhythmic sounds. Manipulation of a record as part of the music, rather than for normal playback or mixing, is called turntablism. The basis of turntablism, and its best known technique, is scratching, pioneered by Grand Wizzard Theodore. It was not until Herbie Hancock's "Rockit" in 1983 that the turntablism movement was recognized in popular music outside of a hip hop context. In the 2010s, many hip hop DJs use DJ CD players or digital record emulator devices to create scratching sounds; nevertheless, some DJs still scratch with vinyl records.

The laser turntable uses a laser as the pickup instead of a stylus in physical contact with the disk. It was conceived of in the late 1980s, although early prototypes were not of usable audio quality. Practical laser turntables are now being manufactured by ELPJ. They are favoured by record libraries and some audiophiles since they eliminate physical wear completely. Experimentation is in progress in retrieving the audio from old records by scanning the disc and analysing the scanned image, rather than using any sort of turntable.

Although largely replaced since the introduction of the compact disc in 1982, record albums still sell in small numbers and are available through numerous sources. In 2008, LP sales grew by 90% over 2007, with 1.9 million records sold.

USB turntables have a built-in audio interface, which transfers the sound directly to the connected computer. Some USB turntables transfer the audio without equalization, but are sold with software that allows the EQ of the transferred audio file to be adjusted. There are also many turntables on the market designed to be plugged into a computer via a USB port for needle dropping purposes.

Responding to longtime calls by fans and disc jockeys, Panasonic Corp. said it is reviving Technics turntables-the series that remains a de facto standard player supporting nightclub music scenes. The new analog turntable, which would come with new direct-drive motor technologies that Panasonic says would improve the quality of sound, would be released sometime between April 2016 and March 2017, the Japanese electronics company announced on September 2, 2015.

Images for kids

An Edison Standard Phonograph that uses wax cylinders

Wood engraving published in The Illustrated Australian News, depicting a public demonstration of new technology at the Royal Society of Victoria (Melbourne, Australia) on 8 August 1878.

Dictionary illustration of a phonautograph. This version uses a barrel made of plaster of Paris.

A Technics SL-1200 turntable

In Spanish: Fonógrafo para niños

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A telephone, also known as a phone, is a communication tool. Originally it was an electric tool transmitting analogue speech along wires. Now it is an electronic tool sending digital signals on wires or radio transmission. Using a telephone, two people who are in different places can talk to each other. Early telephones needed to be connected with wires which are called fixed or landline telephones. Modern mobile phones use radio waves.

Alexander Graham Bell was the first person to patent the telephone, in 1876. Early telephones were wired directly to each other and could only talk to the phone that they were connected to. Later, telephone exchanges allowed connecting to other telephones. During the 20th century the machines that made the connections were automated.

Types of telephones

There are many different types of telephone. A telephone that can be carried around is called a mobile phone or cell phone. These became popular in the late 1980s. It has become common for people to carry mobile phones and in some places it is unusual to not have one. The majority are smartphones, which can be used as computers. Some mobile phones are able to make telephone calls using communications satellites instead of masts on the ground, which means people can make calls from anywhere in the world.

In most countries there are public payphones. To use one, people pay with coins, a credit card or a prepaid card.

Computers can use a machine called a modem or a Digital subscriber line router to talk to other computers over a telephone line. This allows a computer to connect to other computer networks including the Internet.

Most countries have a telephone network. The telephones in one place are connected to a telephone exchange. The exchanges are connected together in a world-wide network. In less developed countries cell phones are used as a cheaper and faster way to connect the countryside to the network.

Telephone number

Most telephones have their own number. Today, telephone numbers are about seven to ten digits long. In many countries, part of the telephone number is called the area code. Area codes are used to make sure the numbers are not the same in two different places. Areas have their own area code, and countries have their own country code.

By the end of 2009, there were a total of nearly 6 billion mobile and fixed-line telephone subscribers worldwide. This included 1.26 billion fixed-line subscribers and 4.6 billion mobile subscribers.

Images for kids

In Spanish: Teléfono para niños

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A bicycle, or bike, is a small, human powered land vehicle with a seat, two wheels, two pedals, and a metal chain connected to cogs on the pedals and rear wheel. A frame gives the bike strength, and the other parts are attached to the frame. The name comes from these two wheels - the prefix "bi-" meaning two, and the suffix "-cycle" meaning wheel. It is powered by a person riding on top, who pushes the pedals around with his or her feet.

Riding bicycles, which is also called cycling, is an important way to travel in several parts of the world. It is also a common recreation, a good form of low-impact exercise, and a popular sport. Road bicycle racing is the second most popular spectator sport in the world. Bicycling uses less energy per mile than any other human transport.

In 1817 a German professor, baron Karl von Drais, created the first two-wheeled bicycle. It was made of wood and had two wheels. The front wheel could be turned using the handlebars in order to steer the bike. However, it did not have pedals, so the rider would have to push their feet on the ground to make it move.

In the 1860s, French inventors added pedals to the front wheel. However, it took a lot of effort to turn the pedals. Later inventors made bikes out of metal only, and made the front wheel very big, giving higher speed. This design was called the penny-farthing bicycle. However, it was difficult to ride, since it could fall easily and the rider would fall far.

Several improvements were made in the 1880s and '90s. In 1885, the safety bicycle was invented. This had two wheels the same size so that the rider could sit at a lower height. It was called the safety bicycle because it much easier to ride than the penny-farthing. When stopping, the rider can simply put down a foot instead of completely dismounting. Instead of pedaling and steering with the front wheel, the safety bicycle steers with the front wheel while the pedals turn the back wheel using a chain. Brakes operated by hand levers on some bikes also increased safety.

In 1888, Scottish inventor John Boyd Dunlop re-invented a type of tire which was filled with air, and this made cycling far more comfortable. Soon, the freewheel was invented. This was a device inside the hub of the back wheel that allowed the wheel to spin even if the rider wasn't pedalling. However, this meant the rider could no longer stop the bike by backpedalling. As a result, a different type of brake was invented which could stop the bike if the pedals were turned backwards. Later inventions included better brakes, and gears which made cycling over hills much easier. During this time the bicycle became very popular.

Basic Design

Basic components common to most bikes include a seat, pedals, gearing, handlebar, wheels, and brakes, all mounted on a frame. The majority also have a gear shifter. The cyclist's feet push the pedals to make them go around in circles, which moves the chain, which turns the back wheel of the bike to make the bike move forwards. The front wheel is connected to the handlebar, so turning the handlebar from side to side swivels the front wheel which steers the bike.

Types of Bicycles

The mountain bicycle is used for riding on rough roads. They have many speeds (usually more than 20), wide tires, and strong wheels. The tire tread is specially designed to ride smoothly on hills, grass, and mountains.

The urban bicycle is made for cities. It`s comfortable and has a relatively high speed. It has a comfortable seat but is heavy. It usually has fenders to keep water and mud from spraying the rider.

The difference between a woman's bicycle and other bicycles is the location of the top tube. When women began to ride bikes, they wore long skirts. The manufacturers of bicycles changed the location of the top tube to make it easier for women to sit down on them while wearing a skirt. Some utility bicycles are similar, for riders who make frequent stops.

The tandem bicycle is made for two people. It has two pairs of pedals. The cyclists sit one behind another. The first cyclist steers the bicycle. There are bicycles for three and more people. There was a bicycle for 40 people.

Folding bicycles can easily be stored in a small place or carried a long distance on an airplane or other public transport.

Electric Bicycles have electric motors, usually inside the hub of either the front or rear wheel. You can choose to ride using the motor only, or with pedals only or with both together. In the U.S. the federal government has set a limit of 750 Watts and a top electric-powered speed of 20MPH to have only the rules that apply to bicycles and no extra restrictions such as operator license, vehicle license, registration or insurance requirements.

A road bicycle usually has narrow wheels, less than 1" (25 mm) wide, with a frame that is much lighter than a mountain bicycle. Road bikes are efficient for longer distances. Many have clips to attach your shoes, rather than just pedals. There are variations, as some road bicycles have regular tires. A road bike can go very fast and is a good choice for a bike race.

When riding on streets, it is safest to ride on the same side of the street that cars drive (which would mean riding on the right side of the road in countries where people drive on the right side of the road, and riding on the left in countries where people drive on the left). To avoid hitting people, riders must obey signs that say "no bicycling", even if it does not seem to make sense at the time. Low light makes bicycle lighting important. It may not be safe to ride when it is dark. Riders wear reflective clothing to be safer in low light. Wearing a helmet makes bicycle riding safer. More than 300,000 people children alone to go to a hospital every year because they were hurt riding a bicycle. Wearing a helmet does not mean that somebody cannot be hurt if they crash their bicycle, but it makes being hurt less likely. Some bicycles have bells or horns that the rider can use to warn other people that they are riding by them.

Related pages

Images for kids

Campana clásica de bicicleta (sonido) 02.wav

Classic bell of a bicycle

Puncture repair kit with tire levers, sandpaper to clean off an area of the inner tube around the puncture, a tube of rubber solution ( vulcanizing fluid), round and oval patches, a metal grater and piece of chalk to make chalk powder (to dust over excess rubber solution). Kits often also include a wax crayon to mark the puncture location.

"Let go - but stand by"; Frances Willard learning to ride a bicycle.

A penny-farthing or ordinary bicycle photographed in the Škoda Auto museum in the Czech Republic

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A bicycle, or bike, is a small, human powered land vehicle with a seat, two wheels, two pedals, and a metal chain connected to cogs on the pedals and rear wheel. A frame gives the bike strength, and the other parts are attached to the frame.