The telephone (from the Greek Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of: τῆλε, tēle, "far" and φωνή, phōnē, "voice"), commonly referred to as a phone, is a telecommunications Telecommunication is the transmission of messages, over significant distances, for the purpose of communication. In earlier times, telecommunications involved the use of visual signals, such as smoke, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded drumbeats, lung-blown horns, or sent by loud whistles, for device that transmits A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications and receives sound Sound is a travelling wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations, most commonly the human voice The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Human voice is specifically that part of human sound production in which the vocal folds are the primary sound source. Generally speaking, the mechanism for generating the human voice can be subdivided into three. Telephones are a point-to-point Point-to-point is sometimes referred to as P2P or Pt2Pt.[citation needed] This usage of P2P is distinct from P2P referring to peer-to-peer file sharing networks communication system whose most basic function is to allow two people separated by large distances to talk to one another. It is one of the most common household appliances Small appliance refers to a class of home appliances that are portable or semi-portable or which are used on tabletops, countertops, or other platforms. Such items are contrasted with major appliances, which are typically fixtures that cannot be easily moved. All appliances are intended to perform, enable, or assist in performing a job or changing in the developed world The term developed country is used to describe countries that have a high level of development according to some criteria. Which criteria, and which countries are classified as being developed, is a contentious issue and is surrounded by fierce debate. Economic criteria have tended to dominate discussions. One such criterion is income per capita;, 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.

All telephones have a microphone A microphone (colloquially called a mic or mike is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1876, Emile Berliner invented the first microphone used as a telephone voice transmitter. Microphones are used in many applications such as telephones, tape recorders, karaoke systems, hearing aids, to speak into, an earphone Headphones are a pair of small loudspeakers, or less commonly a single speaker, with a way of holding them close to a user's ears and a means of connecting them to a signal source such as an audio amplifier, radio or CD player. They are also known as stereophones, headsets or, colloquially cans. The in-ear versions are known as earphones or which reproduces the voice of the other person, a ringer which makes a sound to alert the owner when a call is coming in, and a keypad A telephone keypad is a keypad that appears on a “Touch Tone” telephone. It was standardised when the dual-tone multi-frequency system was introduced in the 1960s, and replaced the rotary dial (or in older phones a telephone dial The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send interrupted electrical pulses, known as pulse dialing, corresponding to the number dialed. The early form of the rotary dial used lugs on a finger plate instead of holes. A patent was filed on August 20, 1896 by employees of Almon Strowger, namely, A) to enter the telephone number A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given verbally to a switchboard operator. As phone systems have grown and interconnected to of the telephone being called. The microphone and earphone are usually built into a handset On a telephone, the handset is a device the user holds to the ear to hear audio. Modern handsets typically contain a microphone as well, but in early telephones the microphone was mounted on the phone itself, which often was attached to a wall at a convenient height for talking. Handsets on such phones were called receivers, a term often applied which is held up to the face to talk. The keypad may be in the handset or in a separate part. A landline A landline was originally an overland telegraph wire, as opposed to an undersea cable. Currently, landline (or land phone or main line or fixed-line) refers to a telephone line which travels through a solid medium, either metal wire or optical fibre, as distinguished from a mobile cellular line, where transmission is via radio waves. Landlines telephone is connected by a wire to the telephone network, while a mobile phone A mobile phone is an electronic device used for full duplex two-way radio telecommunications over a cellular network of base stations known as cell sites. Mobile phones differ from cordless telephones, which only offer telephone service within limited range through a single base station attached to a fixed land line, for example within a home or or cell phone A mobile phone is an electronic device used for full duplex two-way radio telecommunications over a cellular network of base stations known as cell sites. Mobile phones differ from cordless telephones, which only offer telephone service within limited range through a single base station attached to a fixed land line, for example within a home or is portable and communicates with the telephone network by radio Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing some property of the radiated waves, such as. A cordless telephone A cordless telephone or portable telephone is a telephone with a wireless handset that communicates via radio waves with a base station connected to a fixed telephone line, usually within a limited range of its base station . The base station is on the subscriber premises, and attaches to the telephone network the same way a corded telephone does has a portable handset which communicates by radio with a base station connected by wire to the telephone network, and can only be used within a limited range of the base station.

The microphone A microphone (colloquially called a mic or mike is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1876, Emile Berliner invented the first microphone used as a telephone voice transmitter. Microphones are used in many applications such as telephones, tape recorders, karaoke systems, hearing aids, converts the sound waves Sound is a travelling wave which is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations to electrical signals In the fields of communications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity, which are sent through the telephone network The public switched telephone network is the network of the world's public circuit-switched telephone networks. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core and includes mobile as well as fixed telephones to the other phone, where they are converted back to sound waves by the earphone Headphones are a pair of small loudspeakers, or less commonly a single speaker, with a way of holding them close to a user's ears and a means of connecting them to a signal source such as an audio amplifier, radio or CD player. They are also known as stereophones, headsets or, colloquially cans. The in-ear versions are known as earphones or in the other phone's handset. Telephones are a duplex A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions communications medium, meaning they allow the people on both ends to talk at once. The telephone network, consisting of a worldwide net of telephone lines A telephone line or telephone circuit is a single-user circuit on a telephone communications system. Typically this refers to the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user, fiberoptic cables, microwave transmission Microwave transmission refers to the technology of transmitting information by the use of the radio waves whose wavelengths are conveniently measured in small numbers of centimeters, by using various electronic technologies. These are called microwaves. This part of the radio spectrum ranges across frequencies of roughly 1.0 gigahertz to 30 GHz, cellular networks A cellular network is a radio network made up of a number of cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers to communicate with each other and with fixed, communications satellites A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications. Modern communications satellites use a variety of orbits including geostationary orbits, Molniya orbits, other elliptical orbits and low (polar and non-polar) Earth orbits, and undersea telephone cables connected by switching centers A switching center is a node in a telecommunications Circuit switching network which is connected to either another switching center and/or to end user devices. Switching centers are aware of other centers and possible routes between them such that on demand a center can establish an optimal route for a demanded circuit. An optimal route may, allows any telephone in the world to communicate with any other. Each telephone line has an identifying number called its telephone number A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given verbally to a switchboard operator. As phone systems have grown and interconnected to. In order to initiate a telephone call A telephone call is a connection over a telephone network between the calling party and the called party, a conversation with another telephone, the user enters the other telephone's number into a numeric keypad A keypad is a set of buttons arranged in a block or "pad" which usually bear digits and other symbols and usually a complete set of alphabetical letters. If it mostly contains numbers then it can also be called a numeric keypad. Keypads are found on many alphanumeric keyboards and on other devices such as calculators, push-button on his/her phone. Graphic symbols used to designate telephone service or phone-related information in print, signage, and other media include ℡(U+ Unicode is a computing industry standard for the consistent representation and handling of text expressed in most of the world's writing systems. Developed in conjunction with the Universal Character Set standard and published in book form as The Unicode Standard, the latest version of Unicode consists of a repertoire of more than 107,0002121), ☎(U+ Unicode is a computing industry standard for the consistent representation and handling of text expressed in most of the world's writing systems. Developed in conjunction with the Universal Character Set standard and published in book form as The Unicode Standard, the latest version of Unicode consists of a repertoire of more than 107,000260E), ☏(U+ Unicode is a computing industry standard for the consistent representation and handling of text expressed in most of the world's writing systems. Developed in conjunction with the Universal Character Set standard and published in book form as The Unicode Standard, the latest version of Unicode consists of a repertoire of more than 107,000260F), and ✆(U+ Unicode is a computing industry standard for the consistent representation and handling of text expressed in most of the world's writing systems. Developed in conjunction with the Universal Character Set standard and published in book form as The Unicode Standard, the latest version of Unicode consists of a repertoire of more than 107,0002706).

History

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 An invention is a new composition, device, or process. An invention may be derived from a pre-existing model or idea, or it could be independently conceived in which case it may be a radical breakthrough. In addition, there is cultural invention, which is an innovative set of useful social behaviors adopted by people and passed on to others 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 Innocenzo Vincenzo Bartolomeo Luigi Carlo Manzetti was an Italian inventor born in Aosta. Following primary school he went to the Jesuit-run Saint Bénin Boarding School and then on to Turin where he was awarded a diploma in land surveying before returning to Aosta, Antonio Meucci Antonio Meucci was a compatriot of Italian revolutionary Giuseppe Garibaldi, and also an inventor, best known for developing a voice communication apparatus in 1857. Many credit him with the invention of the telephone; for example, the Enciclopedia Italiana di Scienze, Lettere ed Arti (Italian Encyclopedia of Science, Literature and Arts) calls, Johann Philipp Reis Johann Philipp Reis was a self-taught German scientist and inventor of Jewish ancestry, who in 1860-1861 constructed the first telephone, today called the Reis telephone. He is generally regarded as the true inventor of the telephone and was acknowledged as such by both Alexander Graham Bell (who admitted that he drew upon Reis's 1861 device in, Elisha Gray Elisha Gray was an American electrical engineer who co-founded the Western Electric Manufacturing Company. Gray is best known for his development of a telephone prototype in 1876 in Highland Park, Illinois and is considered by some writers to be the true inventor of the variable resistance telephone, despite losing out to Alexander Graham Bell for, Alexander Graham Bell Alexander Graham Bell was an eminent scientist, inventor, engineer and innovator who is credited with inventing the first practical telephone, and Thomas Edison Thomas Alva Edison was an American inventor, scientist, and businessman who developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. Dubbed "The Wizard of Menlo Park" (now Edison, New Jersey) by a newspaper reporter, he, 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 Alexander Graham Bell was an eminent scientist, inventor, engineer and innovator who is credited with inventing the first practical telephone for the electric telephone by the United States Patent and Trademark Office The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification (USPTO) in March 1876.^[2] 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. ^[3]

Basic principles

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 dial-up 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 from the telephone exchange to flow through the line. The exchange detects this current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a modern push-button 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.

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

• 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

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.

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". ^[4] 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 American Telephone & Telegraph Company (AT&T) introduced Touch-Tone dialing 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, 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

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."^[5] 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

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

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
• 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

• Bell System
• Cordless telephone
• Dual-tone multi-frequency signaling
• Harvard sentences
• Satellite phone
• Sidetone
• Telecommunications
• Telephone keypad
• Telephone plug
• Telephone related articles
• Telephone switchboard
• Telephone tapping
• Timeline of the telephone
• Tip and ring (Wiring terminology)
• Videophone

Notes

1. ^ US patent 174465 Alexander Graham Bell: "Improvement in Telegraphy" filed on February 14, 1876, granted on March 7, 1876.
2. ^ Brown, Travis (1994). Historical first patents: the first United States patent for many everyday things (illustrated ed.). University of Michigan: Scarecrow Press. p. 179. ISBN 9780810828988. http://books.google.ca/books?ei=WlVTSuiCE4e-yQS--PDiAg&id=V-NUAAAAMAAJ&dq.
3. ^ "Puskás, Tivadar". Omikk.bme.hu. http://www.omikk.bme.hu/archivum/angol/htm/puskas_t.htm. Retrieved 2010-05-23.
4. ^ "Ringer Boxes". Telephonymuseum.com. http://www.telephonymuseum.com/ringer_boxes.htm. Retrieved 2010-05-23.
5. ^ Sheridan, Barrett. "Newsweek - National News, World News, Health, Technology, Entertainment and more... - Newsweek.com". MSNBC. http://msnbc.msn.com/id/6831938/site/newsweek/. Retrieved 2010-05-23.
6. ^ Next-Generation Networks Set to Transform Communications, International Telecommunications Union website, 4 September 2007. Retrieved 5 July 2009.

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 0-8014-9691-8.

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

• Early U.S. Telephone Industry Data
• 1911 Britannica "Telephone" article
• Virtual museum of early telephones
• The Telephone, 1877
• Modelling Telephone hybrids as 2 x 2 matrices

Categories: 1876 introductions | Discovery and invention controversies | Italian inventions | Office equipment | Telecommunications equipment | Telephony

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