telephone |
celery |
top 10 words in brain distribution (in article): light produce power time common state design bulb allow require |
top 10 words in brain distribution (in article): blade wear horse head form handle century size time shape |
top 10 words in brain distribution (not in article): animal drink lamp water wine beer species bottle cat wolf |
top 10 words in brain distribution (not in article): cell iron steel body type cut design hair metal modern |
times more probable under telephone 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under celery (words not in the model) | |
The telephone'" (from the, "tēle", "far" and φωνή, "phōnē", "voice") is a telecommunications device that is used to transmit and receive electronically or digitally encoded sound (most commonly speech) between two or more people conversing. It is one of the most common household appliances in the developed world today. Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost any other user. Graphic symbols used to designate telephone service or phone-related information in print, signs, and other media include,, and. Basic principle. A traditional landline telephone system, also known as "plain old telephone service" (POTS), commonly handles both signaling and audio information on the same twisted pair of insulated wires: the telephone line. Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication. The signaling equipment consists of a bell, beeper, light or other device to alert the user to incoming calls, and number buttons or a rotary dial to enter a telephone number for outgoing calls. A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference (EMI) and crosstalk than an untwisted pair. A calling party wishing to speak to another party will pick up the telephone's handset, thus operating a button switch or "switchhook", which puts the telephone into an active state or "off hook" by connecting the transmitter (microphone), receiver (speaker) and related audio components to the line. This circuitry has a low resistance (less than 300 Ohms) which causes DC current (48 volts, nominal) from the telephone exchange to flow through the line. The exchange detects this DC current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a modern telephone, the calling party then presses the number buttons in a sequence corresponding to the telephone number of the called party. The buttons are connected to a tone generator that produces DTMF tones which are sent to the exchange. A rotary dial telephone employs pulse dialing, sending electrical pulses corresponding to the telephone number to the exchange. (Most exchanges are still equipped to handle pulse dialing.) Provided the called party's line is not already active or "busy", the exchange sends an intermittent ringing signal (generally over 100 volts AC) to alert the called party to an incoming call. If the called party's line is active, the exchange sends a busy signal to the calling party. However, if the called party's line is active but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call. When a landline phone is inactive or "on hook", its alerting device is connected across the line through a capacitor, which prevents DC current from flowing through the line. The circuitry at the telephone exchange detects the absence of DC current flow and thus that the phone is on hook with only the alerting device electrically connected to the line. When a party initiates a call to this line, the ringing signal transmitted by the telephone exchange activates the alerting device on the line. When the called party picks up the handset, the switchhook disconnects the alerting device and connects the audio circuitry to the line. The resulting low resistance now causes DC current to flow through this line, confirming that the called phone is now active. Both phones being active and connected through the exchange, the parties may now converse as long as both phones remain off hook. When a party "hangs up", placing the handset back on the cradle or hook, DC current ceases to flow in that line, signaling the exchange to disconnect the call. Calls to parties beyond the local exchange are carried over "trunk" lines which establish connections between exchanges. In modern telephone networks, fiber-optic cable and digital technology are often employed in such connections. Satellite technology may be used for communication over very long distances. In most telephones, the transmitter and receiver (microphone and speaker) are located in the handset, although in a speakerphone these components may be located in the base or in a separate enclosure. Powered by the line, the transmitter produces an electric current whose voltage varies in response to the sound waves arriving at its diaphragm. The resulting current is transmitted along the telephone line to the local exchange then on to the other phone (via the local exchange or a larger network), where it passes through the coil of the receiver. The varying voltage in the coil produces a corresponding movement of the receiver's diaphragm, reproducing the sound waves present at the transmitter. A Lineman's handset is a telephone designed for testing the telephone network, and may be attached directly to aerial lines and other infrastructure components. History. Credit for inventing the electric telephone remains in dispute. As with other great inventions such as radio, television, light bulb, and computer, there were several inventors who did pioneer experimental work on voice transmission over a wire and improved on each other's ideas. Innocenzo Manzetti, Antonio Meucci, Johann Philipp Reis, Elisha Gray, Alexander Graham Bell, and Thomas Edison, among others, have all been credited with pioneer work on the telephone. A Hungarian engineer, Tivadar Puskás invented the Telephone exchange in 1876. The early history of the telephone is a confusing morass of claim and counterclaim, which was not clarified by the huge mass of lawsuits which hoped to resolve the patent claims of individuals. The Bell and Edison patents, however, were forensically victorious and commercially decisive. Early commercial instruments. Early telephones were technically diverse. Some used a liquid transmitter, some had a metal diaphragm that induced current in an electromagnet wound around a permanent magnet, and some were "dynamic" -their diaphragm vibrated a coil of wire in the field of a permanent magnet or the coil vibrated the diaphragm. This dynamic kind survived in small numbers through the 20th century in military and maritime applications where its ability to create its own electrical power was crucial. Most, however, used the Edison Berliner carbon transmitter, which was much louder than the other kinds, even though it required an induction coil, actually acting as an impedance matching transformer to make it compatible to the impedance of the line. The Edison patents kept the Bell monopoly viable into the 20th century, by which time the network was more important than the instrument. Early telephones were locally powered, using either a dynamic transmitter or by the powering of a transmitter with a local battery. One of the jobs of outside plant personnel was to visit each telephone periodically to inspect the battery. During the 20th century, "common battery" operation came to dominate, powered by "talk battery" from the telephone exchange over the same wires that carried the voice signals. Early telephones used a single wire for the subscriber's line, with ground return used to complete the circuit (as used in telegraphs). The earliest dynamic telephones also had only one opening for sound, and the user alternately listened and | "Apium graveolens" is a plant species in the family Apiaceae commonly known as celery'" (var. "dulce") or celeriac'" (var. "rapaceum") depending on whether the petioles or roots are eaten. Taxonomy. Celery was described by Carolus Linnaeus in Volume One of his "Species Plantarum" in 1753. The closely related "Apium bermejoi" from the island of Minorca is one of the rarest plants in Europe with only 60 individuals left. Uses. "Apium graveolens" is used around the world as a vegetable, either for the crisp petiole (leaf stalk) or the fleshy taproot. In temperate countries, celery is also grown for its seeds. Actually very small fruit, these "seeds" yield a valuable volatile oil used in the perfume and pharmaceutical industries. They also contain an organic compound called apiol. Celery seeds can be used as flavouring or spice either as whole seeds or, ground and mixed with salt, as celery salt. Celery salt can also be made from an extract of the roots. Celery salt is used as a seasoning, in cocktails (notably to enhance the flavour of Bloody Mary cocktails), on the Chicago-style hot dog, and in Old Bay Seasoning. Celery, onions, and bell peppers are the holy trinity of Louisiana Creole and Cajun cuisine. Celery, onions, and carrots make up the French mirepoix, often used as a base for sauces and soups. Celery is a staple in chicken noodle soup. Celery is an important ingredient in Indian cuisines including in Indian Curry. Celery is widely eaten by guinea pigs, dogs, horses, birds, squirrels, and small rodents. Medicine. The use of celery seed in pills for relieving pain was described by Aulus Cornelius Celsus ca. 30 AD. Nutrition. Celery is valuable in weight-loss diets, where it provides low-calorie fiber bulk. Celery contains androstenone, not androsterone. Bergapten in the seeds can increase photosensitivity, so the use of essential oil externally in bright sunshine should be avoided. The oil and large doses of seeds should be avoided during pregnancy: they can act as a uterine stimulant. Seeds intended for cultivation are not suitable for eating as they are often treated with fungicides. There is a common belief that celery is so difficult for humans to digest, that it has negative calories because human digestion burns more calories than can be extracted. Allergies. Although many people enjoy foods made with celery, a small minority of people can have severe allergic reactions. For people with celery allergy, exposure can cause potentially fatal anaphylactic shock. The allergen does not appear to be destroyed at cooking temperatures. Celery root—commonly eaten as celeriac, or put into drinks—is known to contain more allergen than the stalk. Seeds contain the highest levels of allergen content. Celery is amongst a small group of foods (headed by peanuts) that appear to provoke the most severe allergic reactions (anaphylaxis). Exercise-induced anaphylaxis may be exacerbated. An allergic reaction also may be triggered by eating foods that have been processed with machines that have previously processed celery, making avoiding such foods difficult. In contrast with peanut allergy being most prevalent in the US, celery allergy is most prevalent in Central Europe. In the European Union, foods that contain or may contain celery, even in trace amounts, have to be clearly marked as such. History. Zohary and Hopf note that celery leaves and inflorescences were part of the garlands found in the tomb of Tutankhamun, pharaoh of ancient Egypt, and celery mericarps dated to the 7th century BC were recovered in the Heraion of Samos. However, they note "since "A. graveolens" grows wild in these areas it is hard to decide whether these remains represent wild or cultivated forms." Only by classical times is it certain that celery was cultivated. M. Fragiska mentions an archeological find of celery dating to the 9th century BC, at Kastanas; however, the literary evidence for ancient Greece is far more abundant. In Homer's "Iliad", the horses of Myrmidons graze on wild celery that grows in the marshes of Troy, and in "Odyssey" there is mention of the meadows of violet and wild celery surrounding the cave of Calypso. Cultural depictions. A chthonian symbol, celery was said to have sprouted from the blood of Kadmilos, father of the Cabers, chthonian divinities celebrated in Samothrace, Lemnos and Thebes. The spicy odour and dark leaf colour encouraged this association with the cult of death. In classical Greece celery leaves were used as garlands for the dead, and the wreaths of the winners at the Isthmian Games were first made of celery before being replaced by crowns made of pine. According to Pliny the Elder ("Natural History" XIX.46), in Archaia the garland worn by the winners of the sacred contest at Nemea was also made of celery. Celery is eaten at the end of each adventure by the Wonder Pets in the American animated children's television series. Cultivation. "Apium graveolens" grows to 1 m (3 ft) tall. The leaves are pinnate to bipinnate leaves with rhombic leaflets 3-6 cm long and 2-4 cm broad. The flowers are creamy-white, 2-3 mm diameter, produced in dense compound umbels. The seeds are broad ovoid to globose, 1.5-2 mm long and wide. In North America, commercial production of celery is dominated by a variety called Pascal celery. Gardeners can grow a range of cultivars, many of which differ little from the wild species, mainly in having stouter leaf stems. They are ranged under two classes, white and red; the white cultivars being generally the best flavoured, and the most crisp and tender. The wild form of celery is known as "smallage". It has a furrowed stalk with wedge-shaped leaves, the whole plant having a coarse, earthy taste, and a distinctive smell. With cultivation and blanching, the stalks lose their acidic qualities and assume the mild, sweetish, aromatic taste particular to celery as a salad plant. The plants are raised from seed, sown either in a hot bed or in the open garden according to the season of the year, and after one or two thinnings out and transplantings they are, on attaining a height of 15-20 cm, planted out in deep trenches for convenience of blanching, which is affected by earthing up to exclude light from the stems. In the past, celery was grown as a vegetable for winter and early spring; because of its antitoxic properties, it was perceived as a cleansing tonic, welcomed after the stagnation of winter. Harvesting and storage. Harvesting occurs when the average size of celery in a field is marketable; due to extremely uniform crop growth, fields are harvested only once. Petioles and leaves are removed and harvested celery are packed by size and quality (determined by color, shape, straightness and thickness of petiole, stalk and midrib length and absence of disease, cracks, splits, insect damage and rot). Under optimal conditions, celery can be stored for up to seven weeks between 0 to 2°C (32 to 36°F). Inner stalks may continue growing if kept at temperatures above 0°C (32°F). Freshly-cut petioles of celery are prone to decay, which can be prevented or reduced through the use of sharp blades during processing, gentle handling, and proper sanitation. |