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top 10 words in brain distribution (in article): iron blade steel handle cut metal tool nail hammer hand |
top 10 words in brain distribution (in article): design common power time metal allow modern handle century shape |
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top 10 words in brain distribution (not in article): head hair whip size breast design sword century cell bra |
top 10 words in brain distribution (not in article): animal material size wood species iron steel type build blade |
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times more probable under knife 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under telephone (words not in the model) | |
| A knife'" is a handheld sharp-edged instrument consisting of a handle attached to a blade that is used for cutting. Knives were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools. History. The earliest knives were shaped by knapping (percussive flaking) of rock, particularly harder rocks such as obsidian and flint. During the Paleolithic era Homo habilis likely made similar tools out of wood, bone, and similar perishable materials that have not survived. As recent as five thousand years ago, as advances in metallurgy progressed, stone, wood, and bone blades were gradually succeeded by copper, bronze, iron, and eventually steel. The first metal (copper) knives were symmetrical double edged daggers, which copied the earlier flint daggers. In Europe the first single edged knives appeared during the middle bronze age. Modern knives may be made from many different materials such as alloy tool steels, carbon fiber, ceramics, and titanium. Materials and construction. Today, knives come in many forms but can be generally categorized between two broad types: fixed blade knives and folding, or pocket, knives. Modern knives consist of a "blade" (1'") and "handle" (2'"). The blade edge can be plain or serrated or a combination of both. The handle, used to grip and manipulate the blade safely, may include the "tang", a portion of the blade that extends into the handle. Knives are made with partial (extending part way into the handle) and full (extending the full length of the handle, often visible on top and bottom) tangs. The handle can also include a bolster, which is a piece of material used to balance the knife, usually brass or other metal, at the front of the handle where it meets the blade. The blade consists of the "point" (3'"), the end of the knife used for piercing, the "edge" (4'"), the cutting surface of the knife extending from the point to the heel, the "grind" (5'"), the "cross-section" shape of the blade, the "spine", (6'"), the top, thicker portion of the blade, the "fuller" (7'"), the groove added to lighten the blade, and the "ricasso" (8'"), the thick portion of the blade joining the blade and the handle. The "guard" (9'") is a barrier between the blade and the handle which protects the hand from an opponent, or the blade of the knife itself. A "choil", where the blade is unsharpened and possibly indented as it meets the handle, may be used to prevent scratches to the handle when sharpening or as a forward-finger grip. The end of the handle, or "butt" (10'"), may allow a "lanyard" (11'"), used to secure the knife to the wrist, or a portion of the tang to protrude as a striking surface for pounding or glass breaking. Blade. Knife blades can be manufactured from a variety of materials, each of which has advantages and disadvantages. Carbon steel, an alloy of iron and carbon, can be very sharp, hold its edge well, and remain easy to sharpen, but is vulnerable to rust and stains. Stainless steel is an alloy of iron, chromium, possibly nickel, and molybdenum, with only a small amount of carbon. It is not able to take quite as sharp an edge as carbon steel, but is highly resistant to corrosion. High carbon stainless steel is stainless steel with a higher amount of carbon, intended to incorporate the better attributes of carbon steel and stainless steel. High carbon stainless steel blades do not discolor or stain, and maintain a sharp edge. Laminate blades use multiple metals to create a layered sandwich, combining the attributes of both. For example, a harder, more brittle steel may be sandwiched between an outer layer of softer, tougher, stainless steel to reduce vulnerability to corrosion. In this case, however, the part most affected by corrosion, the edge, is still vulnerable. Pattern-welding is similar to laminate construction. Layers of different steel types are welded together, but then the stock is manipulated to create patterns in the steel. Titanium is metal that has a better strength-to-weight ratio, is more wear resistant, and more flexible than steel. Although less hard and unable to take as sharp an edge, carbides in the titanium alloy allow them to be heat-treated to a sufficient hardness. Ceramic blades are hard, brittle, and lightweight: they may maintain a sharp edge for years with no maintenance at all. They are immune to common corrosion, and can only be sharpened on silicon carbide sandpaper and some grinding wheels. Plastic blades are not especially sharp and typically serrated. They are often disposable. Steel blades are commonly shaped by forging or stock removal. Forged blades are made by heating a single piece of steel, then shaping the metal while hot using a hammer or press. Stock removal blades are shaped by grinding and removing metal. With both methods, after shaping, the steel must be heat treated. This involves heating the steel above its critical point, then quenching the blade to harden it. After hardening, the blade is tempered to remove stresses and make the blade tougher. Mass manufactured kitchen cutlery uses both the forging and stock removal processes. Forging tends to be reserved for manufacturers' more expensive product lines, and can often be distinguished from stock removal product lines by the presence of an integral bolster, though integral bolsters can be crafted through either shaping method. Knives are sharpened in various ways. Flat ground blades have a profile that tapers from the thick spine to the sharp edge in a straight or convex line. Seen in cross section, the blade would form a long, thin triangle, or where the taper does not extend to the back of the blade, a long thin rectangle with one peaked side. Hollow ground blades have concave, beveled edges. The resulting blade has a thinner edge, so it may have better cutting ability for shallow cuts, but it is lighter and less durable than flat ground blades and will tend to bind in deep cuts. Serrated blade knives have a wavy, scalloped or saw-like blade. Serrated blades are more well suited for tasks that require aggressive 'sawing' motions, whereas plain edge blades are better suited for tasks that require push-through cuts (e.g., shaving, chopping). Fixed blade features. A fixed blade knife does not fold or slide, and is typically stronger due to the tang, the extension of the blade into the handle, and lack of moving parts. Folding blade features. A folding knife connects the blade to the handle through a pivot, allowing the blade to fold into the handle. To prevent injury to the knife user through the blade accidentally closing on the user's hand, folding knives typically have a locking mechanism. Different locking mechanisms are favored by various individuals for reasons such as perceived strength (lock safety), legality, and ease of use. Another prominent feature on many folding knives is the opening mechanism. Traditional pocket knives and Swiss Army Knives commonly employ the nail nick, while modern folding knives more often use a stud, hole, disk, or "flipper" located on the blade, all which have the benefit of allowing the user to open the knife with one hand. "Automatic" or "switchblade" knives open using the stored energy from a spring that is released when the user presses a button or lever or other actuator built into the handle of the knife. Automatic knives are popular amongst law enforcement and military users for their ease of rapid deployment and their ability to be opened using only one hand. Automatic knives are severely restricted by law in most states. Increasingly common are "assisted opening" knives which use springs to propel the blade once the user has moved it past a certain angle. These differ from automatic or switchblade knives in that the blade is not released by means of a button or catch on the handle; rather, the blade itself is the actuator. Most assisted openers use flippers as their opening mechanism. Assisted opening knives can be as fast or faster than automatic knives to deploy. Sliding blade features. A sliding knife is a knife which can be opened by sliding the knife blade out the front of the handle. One method of opening is where the blade exits out the front of the handle point-first and then is locked into place (an example of the this is the gravity knife). Another form is a O-T-F (out-the-front) switchblade, which only requires the push of a button or spring to cause the blade to slide out of the handle, and lock into place. To retract the blade back into the handle, a release lever or button, usually the same control as to open, is pressed. A very common form of sliding knife is the sliding utility knife (commonly known as a stanley knife). Handle. The handles of knives can be made from a number of different materials, each of which has advantages and disadvantages. Handles are produced in a wide variety of shapes and styles. Handles are often textured to enhance grip. More exotic materials usually only seen on art or ceremonial knives include: Stone, bone, mammoth tooth, mammoth ivory, oosic (walrus penis bone), walrus tusk, antler (often called stag in a knife context), sheep horn, buffalo horn, teeth, etc. Many materials have been employed in knife handles. Knives as weapons. As a weapon, the knife is universally adopted as an essential tool. For example: Knives as utensils. A primary aspect of the knife as a tool includes dining, used either in food preparation or as cutlery. Examples of this include: Knives as tools. As a utility tool the knife can take many forms, including: Rituals and superstitions. The knife plays a significant role in some cultures through ritual and superstition, as the knife was an essential tool for survival since early man. Knife symbols can be found in various cultures to symbolize all stages of life; for example, a knife placed under the bed while giving birth is said to ease the pain, or, stuck into the headboard of a cradle, to protect the baby.; knives were included in some Anglo-Saxon burial rites, so the dead would not be defenseless in the next world. The knife plays an important role in some initiation rites, and many cultures perform rituals with a variety of knives, including the ceremonial sacrifices of animals. Samurai warriors, as part of bushido, could perform ritual suicide, or seppuku, with a tantō, a common Japanese knife. An athame, a ceremonial black-handled knife, is used in Wicca and derived forms of neopagan witchcraft. In Greece a black-handled knife placed under the pillow is used to keep away nightmares. As early as 1646 reference is made to a superstition of laying a knife across another piece of cutlery being a sign of witchcraft. A common belief is that if a knife is given as a gift, the relationship of the giver and recipient will be severed. Something such as a small coin or dove is exchanged for the gift, rendering "payment." Legislation. Knives are typically restricted by law, although restrictions vary greatly by country or state and type of knife. For example, some laws restrict carrying an unconcealed knife in public while other laws can restrict even private ownership of certain knives, such as switchblades. | 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 spoke (rather, shouted) into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but were more expensive. At first, the benefits of an exchange were not exploited. Telephones instead were leased in pairs to the subscriber, who had to arrange telegraph contractors to construct a line between them, for example between his home and his shop. Users who wanted the ability to speak to several different locations would need to obtain and set up three or four pairs of telephones. Western Union, already using telegraph exchanges, quickly extended the principle to its telephones in New York City and San Francisco, and Bell was not slow in appreciating the potential. Signalling began in an appropriately primitive manner. The user alerted the other end, or the exchange operator, by whistling into the transmitter. Exchange operation soon resulted in telephones being equipped with a bell, first operated over a second wire, and later over the same wire, but with a condenser (capacitor) in series with the bell coil to allow the AC ringer signal through while still blocking DC (keeping the phone "on hook"). Telephones connected to the earliest Strowger automatic exchanges had seven wires, one for the knife switch, one for each telegraph key, one for the bell, one for the push button and two for speaking. Rural and other telephones that were not on a common battery exchange had a magneto or hand-cranked generator to produce a high voltage alternating signal to ring the bells of other telephones on the line and to alert the operator. In the 1890s a new smaller style of telephone was introduced, packaged in three parts. The transmitter stood on a stand, known as a "candlestick" for its shape. When not in use, the receiver hung on a hook with a switch in it, known as a "switchhook." Previous telephones required the user to operate a separate switch to connect either the voice or the bell. With the new kind, the user was less likely to leave the phone "off the hook". In phones connected to magneto exchanges, the bell, induction coil, battery and magneto were in a separate "bell box." In phones connected to common battery exchanges, the bell box was installed under a desk, or other out of the way place, since it did not need a battery or magneto. Cradle designs were also used at this time, having a handle with the receiver and transmitter attached, separate from the cradle base that housed the magneto crank and other parts. They were larger than the "candlestick" and more popular. Disadvantages of single wire operation such as crosstalk and hum from nearby AC power wires had already led to the use of twisted pairs and, for long distance telephones, four-wire circuits. Users at the beginning of the 20th century did not place long distance calls from their own telephones but made an appointment to use a special sound proofed long distance telephone booth furnished with the latest technology. What turned out to be the most popular and longest lasting physical style of telephone was introduced in the early 20th century, including Bell's Model 102. A carbon granule transmitter and electromagnetic receiver were united in a single molded plastic handle, which when not in use sat in a cradle in the base unit. The of the Model 102 shows the direct connection of the receiver to the line, while the transmitter was induction coupled, with energy supplied by a local battery. The coupling transformer, battery, and ringer were in a separate enclosure. The dial switch in the base interrupted the line current by repeatedly but very briefly disconnecting the line 1-10 times for each digit, and the hook switch (in the center of the circuit diagram) permanently disconnected the line and the transmitter battery while the handset was on the cradle. After the 1930s, the base also enclosed the bell and induction coil, obviating the old separate bell box. Power was supplied to each subscriber line by central office batteries instead of a local battery, which required periodic service. For the next half century, the network behind the telephone became progressively larger and much more efficient, but after the dial was added the instrument itself changed little until touch tone replaced the dial in the 1960s. Digital telephony. The Public Switched Telephone Network (PSTN) has gradually evolved towards digital telephony which has improved the capacity and quality of the network. End-to-end analog telephone networks were first modified in the early 1960s by upgrading transmission networks with T1 carrier systems. Later technologies such as SONET and fiber optic transmission methods further advanced digital transmission. Although analog carrier systems existed, digital transmission made it possible to significantly increase the number of channels multiplexed on a single transmission medium. While today the end instrument remains analog, the analog signals reaching the aggregation point (Serving Area Interface (SAI) or the central office (CO)) are typically converted to digital signals. Digital loop carriers (DLC) are often used, placing the digital network ever closer to the customer premises, relegating the analog local loop to legacy status. IP telephony. Internet Protocol (IP) telephony (also known as Voice over Internet Protocol, VoIP), is a disruptive technology that is rapidly gaining ground against traditional telephone network technologies. As of January 2005, up to 10% of telephone subscribers in Japan and South Korea have switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing." As of 2006 many VoIP companies offer service to consumers and businesses. IP telephony uses an Internet connection and hardware IP Phones or softphones installed on personal computers to transmit conversations encoded as data packets. In addition to replacing POTS (plain old telephone service), IP telephony services are also competing with mobile phone services by offering free or lower cost connections via WiFi hotspots. VoIP is also used on private networks which may or may not have a connection to the global telephone network. Usage. By the end of 2006, there were a total of nearly 4 billion mobile and fixed-line subscribers and over 1 billion Internet users worldwide. This included 1.27 billion fixed-line subscribers and 2.68 billion mobile subscribers. Telephone operating companies. In some countries, many telephone operating companies (commonly abbreviated to "telco" in American English) are in competition to provide telephone services. Some of them are included in the following list. However, the list only includes facilities based providers and not companies which lease services from facilities based providers in order to serve their customers. |