telephone

1. To speak with (a person) by telephone.
2. To initiate or make a telephone connection with; place a call to.
3. To transmit (a message, for example) by telephone.

WORD HISTORY   The everyday word telephone illustrates some important linguistic and etymological processes. First, the noun telephone is one of a class of technological and scientific words made up of combining forms derived from classical languages, in this case tele- and -phone. Tele- is from the Greek combining form tēle- or tēl-, a form of tēle, meaning "afar, far off," while -phone is from Greek phōnē, "sound, voice." Such words derived from classical languages can be put together in French or German, for example, as well as in English. Which language actually gave birth to them cannot always be determined. In this case French téléphone (about 1830) seems to have priority. The word was used for an acoustic apparatus, as it originally was in English (1844). Alexander Graham Bell appropriated the word for his invention in 1876, and in 1877 we have the first instance of the verb telephone meaning "to speak to by telephone." The verb is an example of a linguistic process called functional shift. This occurs when a word develops a new part of speech: a noun is used as a verb (to date), a verb as a noun (a break), an adjective as a noun (the rich), a noun as an adjective (a stone wall), or even an adjective as a verb (to round). When we telephone a friend, we are changing the syntactic function of telephone, making it a verb rather than a noun.

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History

Throughout history, people have devised methods for communicating over long distances. The earliest methods involved crude systems such as drum beating or smoke signaling. These systems evolved into optical telegraphy, and by the early 1800s, electric telegraphy. The first simple telephones, which were comprised of a long string and two cans, were known in the early eighteenth century.

A working electrical voice-transmission system was first demonstrated by Johann Philipp Reis in 1863. His machine consisted of a vibrating membrane that opened or closed an electric circuit. While Reis only used his machine to demonstrate the nature of sound, other inventors tried to find more practical applications of this technology. They were found by Alexander Graham Bell in 1876 when he was awarded a patent for the first operational telephone. This invention proved to revolutionize the way people communicate throughout the world.

Bell's interest in telephony was primarily derived from his background in vocal physiology and his speech instruction to the deaf. His breakthrough experiment occurred on June 2, 1875. He and his assistant, Thomas Watson, were working on a harmonic telegraph. When a reed stuck on Watson's transmitter an intermittent current was converted to a continuous current. Bell was able to hear the sound on his receiver confirming his belief that sound could be transmitted and reconverted through an electric wire by using a continuous electric current.

The original telephone design that Bell patented was much different than the phone we know today. In a real sense, it was just a modified version of a telegraph. The primary difference was that it could transmit true sound. Bell continued to improve upon his design. After two years, he created a magnetic telephone which was the precursor to modern phones. This design consisted of a transmitter, receiver, and a magnet. The transmitter and receiver each contained a diaphragm, which is a metal disk. During a phone call, the vibrations of the caller's voice caused the diaphragm in the transmitter to move. This motion was transferred along the phone line to the receiver. The receiving diaphragm began vibrating thereby producing sound and completing the call.

While the magnetic phone was an important breakthrough, it had significant drawbacks. For example, callers had to shout to overcome noise and voice distortions. Additionally, there was a time lapse in the transmission which resulted in nearly incoherent conversations. These problems were eventually solved as the telephone underwent numerous design changes. The first phones made available to consumers used a single microphone. This required the user to speak into it and then put it to the ear to listen. Thomas Edison introduced a model that had a moveable listening earpiece and stationary speaking tube. When placing a call, the receiver was lifted and the user was connected directly to an operator who would then switch wires manually to transmit. In 1878, the first manual telephone exchange was opened. It served 21 customers in New Haven, Connecticut. Use of the telephone spread rapidly and in 1891, the first automatic number calling mechanism was introduced.

Long-distance service was first made available in 1881. However, the transmission rates were not good and it was difficult to hear. In 1900, two workers at Bell System designed loading coils that could minimize distortions. In 1912, the vacuum tube was adapted to the phone as an amplifier. This made it possible to have a transcontinental phone line, first demonstrated in 1915. In 1956, a submarine cable was laid across the Atlantic to allow transatlantic telephone communication. The telecommunication industry was revolutionized in 1962 when orbiting communication satellites were utilized. In 1980, a fiber-optic system was introduced, again revolutionizing the industry.

Background

Telephones still operate on the same basic principles that Bell introduced over one hundred years ago. If a person wishes to make a call, they pick up the handset. This causes the phone to be connected to a routing network. When the numbers are pressed on a touch-tone keypad, signals are sent down the phone line to the routing station. Here, each digit is recognized as a combination of tone frequencies. The specific number combination causes a signal to be sent to another phone causing it to ring. When that phone is picked up, a connection between the two phones is initiated.

The mouthpiece acts as a microphone. Sound waves from the user's voice cause a thin, plastic disk inside the phone to vibrate. This changes the distance between the plastic disk and another metal disk. The intensity of an electric field between the two disks is changed as a result and a varying electric current is sent down the phone line. The receiver on the other phone picks up this current. As it enters the receiver, it passes through a set of electromagnets. These magnets cause a metal diaphragm to vibrate. This vibration reproduces the voice that initiated the current. An amplifier in the receiver makes it easier to hear. When one of the phones is hung up the electric current is broken, causing all of the routing connections to be released.

The system of transmission presented describes what happens during a local call. It varies slightly for other types of calls such as long distance or cellular. Long distance calls are not always connected directly through wires. In some cases, the signal is converted to a satellite dish signal and transmitted via a satellite. For cellular phones, the signal is sent to a cellular antenna. Here, it is sent via radio waves to the appropriate cell phone.

Raw Materials

A variety of raw materials are used for making telephones. Materials range from glass, ceramics, paper, metals, rubber and plastics. The primary components on the circuit board are made from silicon. The outer housing of the phone is typically made of a strong, high-impact resistant polymer. To modify the characteristics of this polymer, various fillers and colorants are used. The speakers require magnetic materials.

Design

Modern telephones come in many shapes and sizes, but they all have the same general features. They consist of a single handset which contains both the transmitter and receiver. The handset rests on the base when the phone is not in use. They also have a dialing system which is either a rotary dial or a touch-tone keypad. Recently, rotary phones have been phased out in favor of the more useful keypad. To alert the consumer that they have an incoming call, phones are equipped with ringers. A wide variety of specialized phones are also produced. Speaker phones are made to allow the consumer to carry on a telephone conversation without holding the handset. Cordless phones are also available. These models do not require direct connection of the handset to the base. Instead the user's voice is converted to radio waves and then sent to the phone base. This, in turn, gets converted to an electric signal and sent down the phone lines. Another type of common phone is the cellular phone. These phones use radio waves and an antenna system to communicate between phones.

The Manufacturing
Process

Since there are so many different parts that go into making a telephone, the components are typically produced by different companies and then assembled by the phone manufacturer. The main components include the internal electronics, the handset, and the various plastic parts.

Plastic parts

• To produce the plastic parts like the base, handset casing, and push buttons, injection molding is typically done. In this process, pellets of plastic polymer are put into the hopper of an injection molding machine. They then pass through a hydraulically controlled screw and are melted. While the screw rotates, the melted plastic is moved through a nozzle and injected into a mold. Just prior to this injection, the two halves of a mold are brought together to form a cavity which matches the shape of the telephone part. While inside the mold, the plastic is held under pressure for a set amount of time and then allowed to cool. As it cools, it hardens and forms into the shape of the part. This mold is coated with chromium to create a shiny surface.
• After a short while, the mold halves are opened and the part is ejected. The mold then closes again and the process begins again. At this point in process, many of the parts are manually inspected to ensure that no significantly damaged parts are used. If there are damaged parts, they are set aside to be remelted and reformed into new parts.

Internal electronics

• The electronic components of the telephone are sophisticated and use the latest in electronic processing technology. The circuit board is produced the same way that boards are made for other types of electronic equipment. The process begins with a board made of non-conducting material that has the electronic configuration printed on it using a conducting material. This board is then passed through a series of machines that place the appropriate chips, diodes, capacitors and other electronic parts in the appropriate places. To prevent damage caused by dust, the process is completed in a specially cleaned room. When completed, it is sent to the next step for soldering.
• To affix the electronic parts to the board, a wave soldering machine is used. Before being put into the machine, the board is washed to remove contaminants. Upon entering, the board is heated using infrared heat. The underside of the board is passed over a wave of molten solder and through capillary action, all of the necessary spots are filled. As the board is allowed to cool, the solder hardens and the pieces stay in place. This creates an electrical connection between the printed circuits and the components.

Assembly and Packaging

• The individual parts are assembled both automatically and manually. The transmitter and receiver are put together by machines. These parts are then fed onto the main assembly line and inserted into the molded headset. Similarly, the internal electronics, including the touch-tone pad, are inserted into the main housing and attached with screws. The headset is then put on the phone base and the phone chord may also be put on.
• After all of the phone pieces are assembled, the completed phones are put in final packaging. Typically, they are wrapped in plastic and put in boxes. A packaging material such as polystyrene is also included to protect the device from damage during shipping. An owner's manual or other literature is included and the box is sealed with tape. The boxes are stacked on pallets, shipped to distributors and finally, customers.

Quality Control

To ensure the quality of each telephone, visual and electrical inspections are done throughout the entire production process and most flaws are detected. Additionally, the each completed phone is tested to make sure it works. Often these tests are done under different environmental conditions such as excessive heat and humidity to simulate the extremes that are experienced in a real life setting. Plastic parts are given torture tests to ensure they will still function even after a level of consumer abuse. For example, the numbers on a touch tone pad are put under a rubber-finger that taps the buttons enough times that it equals forty years of dialing. Since many of the parts that make up the telephone are produced by subcontractors, telephone manufacturers rely heavily on these suppliers for good quality. To ensure consistent manufacturing, most telephone makers set quality specifications for individual parts that the suppliers must meet.

The Future

Telephone technology is improving rapidly. In the future, cordless phones will be designed to be smaller and lighter. They will have wider transmission and better reception ranges. The sound quality will also be improved. Other technologies that integrate the phone with computers and cable television will be commonplace. Dialing systems will also be improved. In a recent demonstration, one company showed a technology that accepted voice command to dial a phone number.

Where to Learn More

Books

Bigelow, Stephen. Understanding Telephone Electronics New York: Butterworth-Heinemann, 1997.

Noll, A. Introduction to Telephones and Telephone Systems. New York: Artech House Publishers, 1998.

Grosvenor, E and M. Wesson. Alexander Graham Bell: The Life and Times of the Man Who Invented the Telephone. Harry N. Abrams Inc., 1997.

Periodicals

Woolley, S. "Dial tones? No, Web tones." Forbes (January 26, 1998).

[Article by: Perry Romanowski]

An instrument containing a transmitter for converting the acoustic signals of a person's voice to electrical signals, a receiver for reconverting electrical signals to acoustic signals, and associated signaling devices (the dial) for communicating with other persons using similar instruments connected to a network. The term telephone also refers to the complicated system of transmission paths and switching points connected to this instrument. See also Telephone service.

The transmitter is a transducer that converts acoustic energy into electric energy. The carbon transmitter was the key to practical telephony because it amplified the power of the speech signal, making it possible to communicate over distances of many miles. Many of these transmitters are still in service, but they are gradually being replaced by designs based on the charged electret (a condenser microphone) or on electrodynamic principles. Both the electret and electrodynamic transmitters use transistors to provide needed power gain; they introduce less distortion than the carbon transmitter. See also Electret transducer; Microphone; Transducer; Transistor.

Transmitters have a frequency-response range from 250 to 5000 Hz. Even though normal human hearing has a much broader frequency response, speech heard on the telephone resembles closely that heard by a listener.

The heart of an electret transmitter is an electrical capacitor formed by the metal on the diaphragm, a conductive coating on top of the metalized lead frame, and the plastic and air between the metal layers. The diaphragm is made of a special plastic that can be given a permanent electrostatic charge (analogous to the magnetization of a permanent magnet). As sound waves entering the sound port cause pressure changes, the diaphragm moves closer to and farther away from the metalized lead frame. This changes the value of capacitance and produces a varying electric voltage which is the analog of the impinging sound-pressure wave. The signal is amplified by the internal amplifier chip to a level which is suitable for transmission on the telephone network.

The receiver transducer operates on the relatively low power used in the telephone circuit; it converts electric energy back into acoustic energy. Unlike a loudspeaker, the telephone receiver is designed for close coupling to the ear. As in the transmitter, careful design of the relationship of the acoustical and electrical elements produces a desired response-frequency characteristic.

There are two common types of receiver units with fixed coil windings, the ring armature receiver and the bipolar receiver. Moving-coil designs, similar to loudspeakers, are also used in some instances. Fixed-coil receivers are designed to have low acoustic impedance and high available power response over the frequency range 350–3500 Hz. Careful control of both the acoustic and electric design parameters is necessary to achieve the desired response and to avoid undesirable resonances. See also Acoustic impedance.

Standard telephone sets typically include two cords: a line cord that connects the instrument to the building wiring and telephone network, and a handset cord that connects the telephone handset to the chassis. Cordless telephones use a two-way radio link between the handset and the base unit, which is similar to the chassis of the standard telephone; this replaces the handset cord. The base unit is connected through a normal line cord to the telephone network.

The cellular radio system is a form of mobile radio telephony. Cellular telephones use a two-way radio link to replace the line cord. The telephone communicates with one of a number of base stations spread in cells throughout the sevice area. As the telephone user changes location, the link is automatically switched from cell to cell to maintain a good connection. See also Mobile radio.

Meaning "sound over distance," it is the end user terminal in a telephone network. It may refer to a desktop unit, portable wireless unit or cellphone.

In 1876, Alexander Graham Bell's words, "Mr. Watson. Come here! I want you!" ushered in the age of telephony. See POTS, PSTN and telephony.

A Century Ago

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verb

To communicate with (someone) by telephone: buzz, call, ring². Informal dial, phone. Idioms: get someone on the horn, give someone abuzzcallring. See words.

Telephone (from Gr.: tele, far, and phone, sound). In 1861, a German scientist, Philip Reis, achieved renown for very nearly inventing the simple telephone. He used an animal ear membrane to receive signals from an oscillating galvanic inductor. The apparatus could only send sounds of constant pitch such as those produced by a single musical note. Reis could not arrange for any financial support nor could he get a patent for his efforts.

The American Alexander Graham Bell achieved a functional telephone system while seeking a way to make sound waves visible to deaf people. His telephone consisted of a microphone and a speaker and he patented it on 14 February 1876, two hours before Elisha Gray of Chicago filed a similar patent. After a long legal battle, the US Supreme Court upheld Bell's patent. Almon Strowger, an undertaker, invented the first automated telephone exchange in 1892 in Kansas City, and his switches were used until the 1970s.

It was some years before the telephone became dependable and portable enough to be adopted by the military, but it was used by the US army in the Spanish-American war, by the British in the Second Boer War, and by the Japanese in the Russo-Japanese war. During WW I field telephones and switchboards were developed. Both sides laid telephone lines involving thousands of miles of wire. The static conditions of trench warfare allowed for extensive telephone use. The chief problem lay in the maintenance of the miles of cable, always disrupted by shellfire and the threat of security from the enemy tapping into the lines and listening to conversations. The telephone had a significant impact on warfare. Larger forces could be controlled from the rear and massed artillery fire could be controlled directly by a forward observer in the trenches.

The weakness of the telephone emerged once mobile warfare became more general in WW II. Troops in the south Pacific had telephone troubles right through 1943. There was a shortage of switchboards, field wire, open wire, insulators, construction troops, and teletype machines. US army field telephones were superior and lighter than German units, but German field switchboards were superior to those of other countries. Great Britain maintained excellent telephone communications from the start of the war. The major German improvements to the telephone in WW II included technical improvements to equipment. Multi-conductor cables were provided for wire communications. They could be reeled out rapidly and as many as four conversations could take place on them at one time. The Germans were the first to use this type of military long-range cable, and they were followed by both British and US forces.

Telephone instruments became more robust and the use of multi-core cable and more sophisticated portable telephone exchanges meant that telephone communication could be relied upon under even the most adverse conditions. Major telephone switchboards of much greater capacity were needed. They were developed, manufactured, and issued for use at all tactical headquarters to satisfy the need for the greatly increased number of telephone channels required to co-ordinate the movements of field units whose mobility had been expanded many times.

The problem of wire maintenance and the possibility of tapping remained, as illustrated by the Anglo-US operation in Berlin in the 1950s, when the main Soviet telegraph and telephone cables were tapped by means of a clandestinely excavated tunnel. On the other hand, landlines were more generally secure than radio, as the success of ULTRA testified. It is a trade-off that continues into the era of digital cellular telephones.

— Danny M. Johnson

The telephone, a speech transmission device, dates from 1876, the year Alexander Graham Bell patented his "Improvements in Telegraphy." Many inventors had been experimenting with acoustics and electricity, among them Thomas Edison, Emil Berliner, and Elisha Gray. Each of these men, as well as Bell's assistant Thomas Watson, contributed modifications that resulted in the telephone we recognize today. Technology has advanced, but the fundamental principles remain the same.

When Bell Telephone Company formed to market its product in 1877, the telegraph was the reigning telecommunication service. Coast-to-coast communication had been possible since 1861, and 2,250 telegraph offices spanned the country. Earlier that year, Western Union had been offered the Bell patent but refused it, only to buy telephone technology from others. Although Bell held the patent for the device, 1,730 other companies were making telephones.

In 1882, the American Bell Telephone Company won a court judgment against Western Union and gained controlling interest in the company, an event that paved the way for modern telephone systems. In 1885, Bell formed a subsidiary, American Telephone & Telegraph (AT&T), which provided a network to which Bell-licensed companies could connect. For the first time, long-distance calling became possible.

As the twentieth century progressed, the importance of telephone service in the daily lives of Americans increased. The Bureau of the Census estimated that in 1920,35 percent of households had telephones. Fifty years later the figure had risen to 90.5 percent. The Bell System manufactured and installed all telephone equipment and provided all the services. As a national monopoly, it had regulated rates. It was often written that Bell was the best telephone system in the world. The 1877 technology start-up had become the largest privately owned industry in United States history with more than 1 million employees and $152 billion in assets in 1983.

However, as the 1960s drew to a close, complaints of poor service and of "Ma Bell's" monopoly attracted government attention. In 1974, the Department of Justice filed an antitrust suit against AT&T that culminated in a 1984 court order that deregulated the industry. Bell Systems had lost its empire, but its pioneering engineers left an indelible mark on the world.

Bell Telephone announced the first transcontinental telephone service at the San Francisco World's Fair in 1915. Radiotelephone service to other countries and ships at sea was available after 1927. A transatlantic cable was laid in 1956. The transmission of calls by microwave began soon after World War II (1939–1945), and Bell Laboratories initiated satellite communications with the launch of Telstar in 1962.

The Bell Systems invention that had the most dramatic impact on the world was the transistor. Unveiled in 1948, it made small electronic devices possible. The transistor was vital to the development of hearing aids, portable radios, and the personal computer.

AT&T introduced modems for data transmission between computers over telephone lines in 1958. A Department of Defense computer network project from 1969 (ARPANET) developed into the Internet by 1992, and the popular World Wide Web appeared in 1994. By 2001,143 million Americans, more than half the population, were communicating online, sending data and audio and video transmissions. Eighty percent of them re-lied on telephone dial-up connections.

Bibliography

Grosvenor, Edwin, and Morgan Wesson. Alexander Graham Bell: The Life and Times of the Man Who Invented the Telephone. New York: Abrams, 1997.

Gwanthmey, Emily, and Ellen Stern. Once Upon a Telephone: An Illustrated Social History. New York: Harcourt Brace, 1994.

Katz, James Everett. Connections: Social and Cultural Studies of the Telephone in American Life. New Brunswick, N.J.: Transaction, 1999.

Noll, A. Michael. Introduction to Telephones and Telephone Systems. Norwood, Mass.: Artech House, 1999.

n.

An invention of the devil which abrogates some of the advantages of making a disagreeable person keep his distance.

The telephone is a symbol of communication with multiple meanings. If the dreamer is not available, does not want to answer the ringing telephone, or hangs up it may indicate that communication from the unconscious is being ignored.

"Phone" redirects here. For other uses, see Phone (disambiguation).

For other uses, see Telephone (disambiguation).

Telephone

A 1970's era AT&T 'touch-tone' telephone
Inventor	Alexander Graham Bell
Launch year	1876
Available?	Worldwide

The telephone (from the Greek: τῆλε, tēle, "far" and φωνή, phōnē, "voice") is a telecommunications device that transmits and receives sound, most commonly the human voice. It is one of the most common household appliances in the developed world, and has long been considered indispensable to business, industry and government. The word "telephone" has been adapted to many languages and is widely recognized around the world.

The device operates principally by converting sound waves into electrical signals, and electrical signals into sound waves. Such signals when conveyed through telephone networks — and often converted to electronic and/or optical signals — enable nearly every telephone user to communicate with nearly every other worldwide. Graphic symbols used to designate telephone service or phone-related information in print, signage, and other media include ℡(U+2121), ☎(U+260E), ☏(U+260F), and ✆(U+2706).

Contents 1 History 2 Basic principles 2.1 Early development 2.2 Early commercial instruments 3 Digital telephony 4 IP telephony 5 Usage 6 Telephone operating companies 7 Patents 8 See also 9 References 10 Additional references 11 Further reading 12 External links

History

Main articles: History of the telephone and Timeline of the telephone

Credit for the invention of the electric telephone is frequently disputed, and new controversies over the issue have arisen from time-to-time. As with other great inventions such as radio, television, light bulb, and computer, there were several inventors who did pioneering 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 pioneering work on the telephone. An undisputed fact is that Alexander Graham Bell was the first to be awarded a patent for the electric telephone by the United States Patent and Trademark Office (USPTO) in March 1876.^[1] That first patent by Bell was the master patent of the telephone, from which all other patents for electric telephone devices and features flowed.

The early history of the telephone became and still remains a confusing morass of claims and counterclaims, which were not clarified by the huge mass of lawsuits that hoped to resolve the patent claims of many individuals and commercial competitors. The Bell and Edison patents, however, were forensically victorious and commercially decisive.

A Hungarian engineer, Tivadar Puskás quickly invented the telephone switchboard in 1876, which allowed for the formation of telephone exchanges, and eventually networks. ^[2]

Further information: Invention of the telephone, Elisha Gray and Alexander Bell telephone controversy, and Canadian Parliamentary Motion on Alexander Graham Bell

Basic principles

1896 Telephone from Sweden.

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.

The telephone consists of an alerting device, usually a ringer, that remains connected to the phone line whenever the phone is "on hook", and other components which are connected when the phone is "off hook". These include a transmitter (microphone), a receiver (speaker) and other circuits for dialing, filtering, and amplification. 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 (off hook) state 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 circuit that produces DTMF tones which end up at a circuit at 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 (about 90 volts AC in North America and UK and 60 volts in Germany) 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.

The phone's ringer is connected to the line through a capacitor, a device which blocks the flow of DC current but permits AC current. This constitutes a mechanism whereby the phone draws no current when it is on hook, but exchange circuitry can send an AC voltage down the line to activate the ringer for an incoming call. When a landline phone is inactive or "on hook", the circuitry at the telephone exchange detects the absence of DC current flow and therefore "knows" 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, and the ringing signal is transmitted. When the called party picks up the handset, they actuate a double-circuit switchhook which simultaneously disconnects the alerting device and connects the audio circuitry to the line. This, in turn, draws DC current through the line, confirming that the called phone is now active. The exchange circuitry turns off the ring signal, and both phones are now 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.

Further information: Telephone call

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.

Early development

Early telephone with hand cranked generator.

• 1844 — Innocenzo Manzetti first mooted the idea of a “speaking telegraph” (telephone).
• 26 August 1854 — Charles Bourseul publishes an article in a magazine L'Illustration (Paris) : "Transmission électrique de la parole" [electric transmission of speech].
• 26 October 1861 — Johann Philipp Reis (1834–1874) publicly demonstrated the Reis telephone before the Physical Society of Frankfurt
• 22 August 1865, La Feuille d'Aoste reported “It is rumored that English technicians to whom Mr. Manzetti illustrated his method for transmitting spoken words on the telegraph wire intend to apply said invention in England on several private telegraph lines.”
• 28 December 1871 — Antonio Meucci files a patent caveat (n.3335) in the U.S. Patent Office titled "Sound Telegraph", describing communication of voice between two people by wire.
• 1874 — Meucci, after having renewed the caveat for two years, fails to find the money to renew it. The caveat lapses.
• 6 April 1875 — Bell's U.S. Patent 161,739 "Transmitters and Receivers for Electric Telegraphs" is granted. This uses multiple vibrating steel reeds in make-break circuits.
• 11 February 1876 — Gray invents a liquid transmitter for use with a telephone but does not build one.
• 14 February 1876 — Elisha Gray files a patent caveat for transmitting the human voice through a telegraphic circuit.
• 14 February 1876 — Alexander Bell applies for the patent "Improvements in Telegraphy", for electromagnetic telephones using undulating currents.
• 19 February 1876 — Gray is notified by the U.S. Patent Office of an interference between his caveat and Bell's patent application. Gray decides to abandon his caveat.
• 7 March 1876 — Bell's U.S. patent 174,465 "Improvement in Telegraphy" is granted, covering "the method of, and apparatus for, transmitting vocal or other sounds telegraphically … by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound."
• 10 March 1876 — The first successful telephone transmission of clear speech using a liquid transmitter when Bell spoke into his device, “Mr. Watson, come here, I want to see you.” and Watson heard each word distinctly.
• 30 January 1877 — Bell's U.S. patent 186,787 is granted for an electromagnetic telephone using permanent magnets, iron diaphragms, and a call bell.
• 27 April 1877 — Edison files for a patent on a carbon (graphite) transmitter. The patent 474,230 was granted 3 May 1892, after a 15 year delay because of litigation. Edison was granted patent 222,390 for a carbon granules transmitter in 1879.

Early commercial instruments

Modern emergency telephone powered by sound alone.

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. The 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 port opening for sound, with the user alternately listening and speaking (or rather, shouting) into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but also more expensive.

At first, the benefits of a telephone exchange were not exploited. Instead telephones were leased in pairs to a subscriber, who had to arrange for a telegraph contractor to construct a line between them, for example between a home and a 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.

A U.S. candlestick telephone in use, circa 1915.

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 called a "ringer box." ^[3] In phones connected to common battery exchanges, the ringer 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 circuit diagram 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) 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 ringer 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

Main article: 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, designed to support the basic 3 kHZ voice channel by sampling the bandwidth-limited analog voice signal and encoding using PCM. While digitization allows wideband voice on the same channel, the improved quality of a wider analog voice channel did not find a large market in the PSTN.

Later transmission methods such as SONET and fiber optic transmission further advanced digital transmission. Although analog carrier systems existed that multiplexed multiple analog voice channels onto a single transmission medium, digital transmission allowed lower cost and more channels multiplexed on the transmission medium. Today the end instrument often remains analog but the analog signals are typically converted to digital signals at the (Serving Area Interface (SAI), central office (CO), or other aggregation point. Digital loop carriers (DLC) place the digital network ever closer to the customer premises, relegating the analog local loop to legacy status.

IP telephony

Hardware-based IP phone.

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." [1] 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.

IP telephones have two notable disadvantages compared to traditional telephones. Unless the IP telephone's components are backed up with an uninterruptible power supply or other emergency power source, the phone will cease to function during a power outage as can occur during an emergency or disaster, exactly when the phone is most needed. Traditional phones connected to the older PSTN network do not experience that problem since they are powered by the telephone company's battery supply, which will continue to function even if there's a prolonged power black-out. A second distinct problem for an IP phone is the lack of a 'fixed address' which can impact the provision of emergency services such as police, fire or ambulance, should someone call for them. Unless the registered user updates the IP phone's physical address location after moving to a new residence, emergency services can be, and have been, dispatched to the wrong location.

Usage

Fixed telephone lines per 100 inhabitants 1997-2007

By the end of 2006, there were a total of nearly 4 billion mobile and fixed-line subscribers worldwide. This included 1.27 billion fixed-line subscribers and 2.68 billion mobile subscribers. ^[4]

Telephone operating companies

Main article: List of telephone operating companies

In some countries, many telephone operating companies (commonly abbreviated to telco in American English) are in competition to provide telephone services. The above Main article lists only facilities based providers and not companies which lease services from facilities based providers in order to serve their customers.

Patents

• US 174,465 -- Telegraphy (Bell's first telephone patent) -- Alexander Graham Bell
• US 186,787 -- Electric Telegraphy (permanent magnet receiver) -- Alexander Graham Bell
• US 474,230 -- Speaking Telegraph (graphite transmitter) -- Thomas Edison
• US 203,016 -- Speaking Telephone (carbon button transmitter) -- Thomas Edison
• US 222,390 -- Carbon Telephone (carbon granules transmitter) -- Thomas Edison

Look up cordless telephone in Wiktionary, the free dictionary.

• US 485,311 -- Telephone (solid back carbon transmitter) -- Anthony C. White (Bell engineer) This design was used until 1925 and installed phones were used until the 1940s.
• US 3,449,750 -- Duplex Radio Communication and Signalling Appartus -- G. H. Sweigert
• US 3,663,762 -- Cellular Mobile Communication System -- Amos Edward Joel (Bell Labs)
• US 3,906,166 -- Radio Telephone System (DynaTAC cell phone) -- Martin Cooper et al. (Motorola)

See also

Look up telephone in Wiktionary, the free dictionary.

• Bell System
• Cordless telephone
• Dial tone
• Elisha Gray and Alexander Bell telephone controversy
• Harvard sentences
• History of the telephone
• Invention of the telephone
• Local loop
• Mobile phone
• Plain old telephone service
• Public switched telephone network
• Satellite phone
• Sidetone
• Telecommunications
• Telephone call
• Telephone exchange
• Telephone line
• Telephone number
• Telephone plug
• Telephone related articles
• Telephone switchboard
• Telephone tapping
• Telephony
• Timeline of the telephone
• Tip and ring (Wiring terminology)

References

1. ^ Brown, Travis (1994). Historical first patents: the first United States patent for many everyday things (illustrated ed.). University of Michigan: Scarecrow Press. pp. 179. ISBN 9780810828988. http://books.google.ca/books?ei=WlVTSuiCE4e-yQS--PDiAg&id=V-NUAAAAMAAJ&dq. 
2. ^ http://www.omikk.bme.hu/archivum/angol/htm/puskas_t.htm
3. ^ http://www.telephonymuseum.com/ringer_boxes.htm
4. ^ Next-Generation Networks Set to Transform Communications, International Telecommunications Union website, 4 September 2007. Accessed 5 July 2009.

Additional references

• Coe, Lewis (1995), The Telephone and Its Several Inventors: A History. Jefferson, North Carolina: McFarland & Co., Inc. ISBN 0-7864-0138-9
• Evenson, A. Edward (2000), The Telephone Patent Conspiracy of 1876: The Elisha Gray - Alexander Bell Controversy. Jefferson, North Carolina: McFarland & Co., Inc. ISBN 0-7864-0883-9
• Baker, Burton H. (2000), The Gray Matter: The Forgotten Story of the Telephone. St. Joseph, Michigan: Telepress. ISBN 0-615-11329-X
• Huurdeman, Anton A. (2003), The Worldwide History of Telecommunications. Hoboken: New Jersey: Wiley-IEEE Press. ISBN 978-0-471-20505-0
• Josephson, Matthew (1992), Edison: A Biography. Hoboken, New Jersey: John Wiley & Sons, Inc. ISBN 0-471-54806-5
• Bruce, Robert V. (1990), Bell: Alexander Graham Bell and the Conquest of Solitude. Ithaca, New York: Cornell University Press. ISBN 0801496918.

Further reading

• Sobel, Robert (1974), The Entrepreneurs: Explorations Within the American Business Tradition. Weybright & Talley. ISBN 0-679-40064-8.
• Todd, Kenneth P. (1998), A Capsule History of the Bell System. American Telephone & Telegraph Company (AT&T).

External links

Wikimedia Commons has media related to: Telephone

• 1911 Britannica "Telephone" article
• Virtual museum of early telephones
• The Telephone, 1877
• Modelling Telephone hybrids as 2 x 2 matices

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - telefon
v. tr. - telefonere til, ringe til
v. intr. - telefonere

idioms:

• on the telephone    ringe, tale i telefon
• over the telephone    via telefonen
• telephone exchange    telefoncentral
• telephone kiosk    telefonboks
• telephone operator    telefonist

Nederlands (Dutch)
telefoon(toestel), telefoneren

Français (French)
n. - téléphone
v. tr. - téléphoner
v. intr. - téléphoner

idioms:

• on the telephone    au téléphone, sur la ligne
• over the telephone    au téléphone
• telephone exchange    centrale téléphonique
• telephone kiosk    cabine téléphonique
• telephone operator    standardiste

Deutsch (German)
n. - Telefon, Fernsprechapparat
v. - telefonieren, anrufen, telefonisch übermitteln

idioms:

• on the telephone    am Telefon, ans Telefonnetz angeschlossen
• over the telephone    per Telefon
• telephone exchange    Fernmeldeamt
• telephone kiosk    Telefonzelle
• telephone operator    Telefonist

Ελληνική (Greek)
n. - τηλέφωνο
v. - τηλεφωνώ

idioms:

• on the telephone    τηλεφωνικά, συνδεδεμένος τηλεφωνικά
• over the telephone    τηλεφωνικά, από το τηλέφωνο
• telephone exchange    τηλεφωνικό κέντρο, τηλεφωνικός μεταλλάκτης
• telephone kiosk    τηλεφωνικός θάλαμος
• telephone operator    τηλεφωνητής ή τηλεφωνήτρια

Italiano (Italian)
telefonare, telefono

idioms:

• on the telephone    al telefono
• over the telephone    per telefono
• telephone exchange    centralino
• telephone operator    centralinista

Português (Portuguese)
n. - telefone (m)
v. - telefonar

idioms:

• on the telephone    por telefone, ao telefone
• over the telephone    pelo telefone
• telephone exchange    estação telefônica
• telephone operator    telefonista

Русский (Russian)
телефонировать, телефон, система такой аппаратуры, номер такого аппарата

idioms:

• on the telephone    (кто-л.) находится на телефонной линии, наличие телефонного аппарата, присоединенного к телефонной сети
• over the telephone    по телефону
• telephone exchange    телефонная станция
• telephone operator    телефонист/ка

Español (Spanish)
n. - teléfono
v. tr. - llamar por teléfono, telefonear
v. intr. - llamar por teléfono, telefonear

idioms:

• on the telephone    estar hablando por teléfono
• over the telephone    por teléfono
• telephone exchange    central telefónica
• telephone kiosk    cabina telefónica
• telephone operator    operador, telefonista

Svenska (Swedish)
n. - telefon
v. - telefonera, ringa, ringa upp

中文（简体）(Chinese (Simplified))
电话, 电话机, 打电话给, 打电话告知, 打电话, 通电话

idioms:

• on the telephone    在打电话, 用电话, 装有电话机的
• over the telephone    用电话, 通电话
• telephone exchange    电信局
• telephone kiosk    电话亭
• telephone operator    话务员, 接线员

中文（繁體）(Chinese (Traditional))
n. - 電話, 電話機
v. tr. - 打電話給, 打電話告知
v. intr. - 打電話, 通電話

idioms:

• on the telephone    在打電話, 用電話, 裝有電話機的
• over the telephone    用電話, 通電話
• telephone exchange    電信局
• telephone kiosk    電話亭
• telephone operator    話務員, 接線生, 總機

한국어 (Korean)
n. - 전화, 전화기
v. tr. - 전화를 걸다, 전화로 신청하여 보내다
v. intr. - 전화를 걸다, 전화로 부르다

idioms:

• over the telephone    ~와 전화로 통화하다

日本語 (Japanese)
n. - 電話
v. - 電話をかける, 電話で伝える

idioms:

• on the telephone    電話中で
• over the telephone    電話で
• telephone exchange    電話交換局
• telephone kiosk    公衆電話ボックス
• telephone operator    電話交換手
• telephone service    テレホンサービス

العربيه (Arabic)
‏(الاسم) الهاتف, تلفون (فعل) يخاطب تلفونيا‏

עברית (Hebrew)
n. - ‮טלפון, מכשיר טלפון, רשת טלפונים‬
v. tr. - ‮דיבר בטלפון, שלח (מסר) בטלפון‬
v. intr. - ‮טילפן, צילצל, התקשר‬

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