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For other uses, see Telephone (disambiguation).
Touch Tone® single line business telephone with message waiting lamp
Touch Tone® single line business telephone with message waiting lamp

The telephone (from the Greek words tele (τηλέ) = far and phone (φωνή) = voice) is a telecommunications device that is used to transmit and receive sound (most commonly speech), usually two people conversing but occasionally three or more. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly For biologic transmitters see Transmitter substance. A transmitter is an electronic device which usually with the aid of an antenna Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies It is one of the most common household appliances in the world today. Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost anyone. In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the

Contents

Basic principle

1896 Telephone (Sweden)
1896 Telephone (Sweden)

A traditional landline telephone system, or "plain old telephone service" (POTS), commonly handles both signaling and audio information on the same twisted pair of insulated wires: the telephone line. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out A telephone line or telephone circuit (or just line or circuit within the Industry) is a single-user circuit on a Telephone Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication. Fax (short for facsimile, from Latin fac simile, "make similar" i The Internet is a global system of interconnected Computer networks 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 telephone number or phone number is a sequence of numbers used to call from one Telephone line to another in a Telephone network. A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference (EMI) and crosstalk than an untwisted pair. In Electronics, the term crosstalk ( XT) refers to any phenomenon by which a signal transmitted on one circuit or channel of a Transmission system

A calling party wishing to speak to another party will pick up the telephone's handset, thus operating a button switch or "switchhook", which puts the telephone into an active state or "off hook" by connecting the transmitter (microphone), receiver (speaker) and related audio components to the line. The calling party (also called caller, call originator or A-party) is a person who (or device that Initiates a Telephone call over A transceiver is a device that has both a Transmitter and a receiver which are combined and share common circuitry or a single housing In Telephony, the term off-hook has the following meanings The condition that exists when a Telephone or other user instrument is in For the Marty Friedman album see Loudspeaker (album A loudspeaker, speaker, or speaker system is an electroacoustical 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 ohm (symbol Ω) is the SI unit of Electrical impedance or in the Direct current case Electrical resistance, Direct current ( DC) is the unidirectional flow of Electric charge. The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. In the field of Telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls The exchange detects this DC current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. A dial tone (known in the British Isles as a dialling tone) is a Telephony signal used to indicate that the Telephone exchange is working On a modern telephone, the calling party then presses the number buttons in a sequence corresponding to the telephone number of the called party. The buttons are connected to a tone generator that produces DTMF tones which are sent to the exchange. Dual-tone multi-frequency ( DTMF) signaling is used for Telephone signaling over the line in the voice-frequency band to the call switching center A rotary dial telephone employs pulse dialing, sending electrical pulses corresponding to the telephone number to the exchange. Pulse dialing, dial pulse, or loop disconnect dialing, also called Rotary or Decadic dialling in the United Kingdom (because up to 10 pulses (Most exchanges are still equipped to handle pulse dialing. ) Provided the called party's line is not already active or "busy", the exchange sends an intermittent ringing signal (generally over 100 volts AC) to alert the called party to an incoming call. A ringtone or ring tone is the sound made by a Mobile phone to indicate an incoming call or text message An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant If the called party's line is active, the exchange sends a busy signal to the calling party. A busy signal (or busy tone or engaged tone) in telephony is an audible or visual signal to the Calling party that indicates failure to 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. Call waiting (or catch phone in Japan in Telephony, is a feature on some telephone networks

When a landline phone is inactive or "on hook", its alerting device is connected across the line through a capacitor, which prevents DC current from flowing through the line. In Telephony, the term on-hook has the following meanings The condition that exists when a Telephone or other user instrument is not A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors The circuitry at the telephone exchange detects the absence of DC current flow and thus that the phone is on hook with only the alerting device electrically connected to the line. When a party initiates a call to this line, the ringing signal transmitted by the telephone exchange activates the alerting device on the line. When the called party picks up the handset, the switchhook disconnects the alerting device and connects the audio circuitry to the line. The resulting low resistance now causes DC current to flow through this line, confirming that the called phone is now active. Both phones being active and connected through the exchange, the parties may now converse as long as both phones remain off hook. When a party "hangs up", placing the handset back on the cradle or hook, DC current ceases to flow in that line, signaling the exchange to disconnect the call. A telephone call is a connection over a Telephone network between the Calling party and the Called party.

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. Fiber-optic communication is a method of transmitting information from one place to another by sending Light through an Optical fiber. Digital Multiplex System (DMS is the name shared among several different telephony product lines from Nortel Networks for wireline and wireless operators Satellite technology may be used for communication over very long distances. A communications satellite (sometimes abbreviated to comsat) is an artificial Satellite stationed in space for the purposes of Telecommunications.

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. A transceiver is a device that has both a Transmitter and a receiver which are combined and share common circuitry or a single housing A speakerphone is a Telephone with a Microphone and Loudspeaker provided separately from those in the handset Powered by the line, the transmitter produces an electric current which varies in response to the sound waves arriving at its diaphragm. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies In a Loudspeaker, a diaphragm (also known as the cone) is the thin semi-rigid membrane attached to the central Magnet. The resulting electric current is transmitted along the telephone line to the local exchange and then to the other phone (via the local exchange or a larger network), where it passes through the coil of the receiver. A voice coil (consisting of a Bobbin, Collar and Winding) is the Coil of Wire attached to the apex of the cone of a Loudspeaker The varying electric current in the coil causes the receiver's diaphragm to move in and out, 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. A lineman's handset is a special type of Telephone used by technicians for installing and testing Local loop Telephone lines It may also

History

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

Credit for inventing the electric telephone remains in dispute. The history of the telephone chronicles the development of electrical technology that enabled bidirectional human speech conversations over distances farther than a person could Below is a Timeline of the telephone that covers important dates in the History of the telephone. As with other great inventions such as radio, television, light bulb, and computer, there were several inventors who did pioneer experimental work on voice transmission over a wire and improved on each other's ideas. An invention is a new form composition of matter device or Process. Innocenzo Manzetti, Antonio Meucci, Johann Philipp Reis, Elisha Gray, Alexander Graham Bell, and Thomas Edison, among others, have all been credited with pioneer work on the telephone. Innocenzo Vincenzo Bartolomeo Luigi Carlo Manzetti ( 17 March 1826 &ndash 17 March 1877) was born in the Aosta Valley. Antonio Meucci ( Florence, April 13, 1808 &ndash October 18, 1889) was an Italian -born inventor who developed a form of Johann Philipp Reis ( January 7, 1834 &ndash January 14, 1874) was a self-taught German scientist and inventor who in 1860-1 constructed Elisha Gray (August 2 1835 &ndash January 21 1901 was an American electrical engineer and is best known for his development of a telephone prototype in 1876 in WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

The early history of the telephone is a confusing morass of claim and counterclaim, which was not clarified by the huge mass of lawsuits which hoped to resolve the patent claims of individuals. The Bell and Edison patents, however, were forensically victorious and commercially decisive.

Further information: Invention of the telephone and Elisha Gray and Alexander Bell Controversy

Early development

Early commercial instruments

Early telephones were technically diverse. Some used a liquid transmitter, some had a metal diaphragm that induced current in an electromagnet wound around a permanent magnet, and some were "dynamic" - their diaphragm vibrated a coil of wire in the field of a permanent magnet or the coil vibrated the diaphragm. This dynamic kind survived in small numbers through the 20th century in military and maritime applications where its ability to create its own electrical power was crucial. Most, however, used the Edison/Berliner carbon transmitter, which was much louder than the other kinds, even though it required an induction coil, actually acting as an impedance matching transformer to make it compatible to the impedance of the line. An induction coil or "spark coil" ( archaically known as a Ruhmkorff coil) is a type of Disruptive discharge Coil. Impedance matching is the electronics design practice of setting the Output impedance ( Z S of a signal source equal to the Input impedance ( 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. In Telecommunication, the term outside plant has the following meanings In civilian Telecommunications, all cables conduits ducts poles 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. In the field of Telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls Late in the century, wireless handsets brought a revival of local battery power.

Early telephones had one wire for both transmitting and receiving of audio, with ground return as used in telegraphs. Single wire earth return (SWER or single wire ground return is a Single-wire transmission line for supplying single-phase electrical power The earliest dynamic telephones also had only one opening for sound, and the user alternately listened and spoke (rather, shouted) into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but were more expensive.

At first, the benefits of an exchange were not exploited. Telephones instead were leased in pairs to the subscriber, who had to arrange telegraph contractors to construct a line between them, for example between his home and his shop. The subscription business model is a Business model where a customer must pay a subscription price to have access to the product/service 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. The Western Union Company ( is a financial services and communications company based in the United States. The City of New York The City and County of San Francisco is the fourth most populous city

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 with the same wire using a condenser (capacitor). A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors 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. Almon Brown Strowger (1839 &ndash May 26 1902 gave his name to the electromechanical Telephone exchange technology that his invention and Patent inspired In the field of Telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls A switch is a mechanical device used to connect and disconnect an electric Circuit at will Telegraph key, also known as a Morse key, are generic terms for any switching device used primarily to send Morse code.

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. This article is about the Engine component For other uses of the term see Magneto (disambiguation.

In the 1890s a new smaller style of telephone was introduced, packaged in three parts. The transmitter stood on a stand, known as a "candlestick" for its shape. When not in use, the receiver hung on a hook with a switch in it, known as a "switchhook. " Previous telephones required the user to operate a separate switch to connect either the voice or the bell. With the new kind, the user was less likely to leave the phone "off the hook". In phones connected to magneto exchanges, the bell, induction coil, battery and magneto were in a separate "bell box. " In phones connected to common battery exchanges, the bell box was installed under a desk, or other out of the way place, since it did not need a battery or magneto.

Cradle designs were also used at this time, having a handle with the receiver and transmitter attached, separate from the cradle base that housed the magneto crank and other parts. They were larger than the "candlestick" and more popular.

Disadvantages of single wire operation such as crosstalk and hum from nearby AC power wires had already led to the use of twisted pairs and, for long distance telephones, four-wire circuits. In Electronics, the term crosstalk ( XT) refers to any phenomenon by which a signal transmitted on one circuit or channel of a Transmission system Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out In Telecommunication, a four-wire circuit is a two-way circuit using two paths so arranged that the respective signals are transmitted in one direction 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. Long distance in Telecommunications, refers to Telephone calls made outside a certain area usually characterized by an Area code outside of a Local

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. The Model 102 telephone was Western Electric's first widely distributed telephone set to feature the transmitter and receiver in a common handset 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 carbon Microphone, also known as a carbon button microphone (or sometimes just a button microphone) or a carbon transmitter, is a sound-to-electrical 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) permanently disconnected the line and the transmitter battery while the handset was on the cradle. 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

After the 1930s, the base also enclosed the bell and induction coil, obviating the old separate bell box. Power was supplied to each subscriber line by central office batteries instead of a local battery, which required periodic service. For the next half century, the network behind the telephone became progressively larger and much more efficient, but after the dial was added the instrument itself changed little until touch tone replaced the dial in the 1960s.

Digital telephony

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. Digital telephony is the use of digital electronics in the provision of digital Telephone services and systems The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the End-to-end analog telephone networks were first modified in the early 1960s by upgrading transmission networks with T1 carrier systems. An analog or analogue signal is any continuous signal for which the time varying feature (variable of the signal is a representation of some other Later technologies such as SONET and fiber optic transmission methods further advanced digital transmission. Synchronous optical networking (SONET and Synchronous Digital Hierarchy (SDH are two closely related Multiplexing protocols for transferring multiple An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length Although analog carrier systems existed, digital transmission made it possible to significantly increase the number of channels multiplexed on a single transmission medium. For multiplexing in electronics and signal processing see Multiplexer. While today the end instrument remains analog, the analog signals reaching the aggregation point (Serving Area Interface (SAI) or the central office (CO) ) are typically converted to digital signals. The serving area interface or service area interface ( SAI In the field of Telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls The term digital signal is used to refer to more than one concept Digital loop carriers (DLC) are often used, placing the digital network ever closer to the customer premises, relegating the analog local loop to legacy status. A digital loop carrier (DLC is a system which uses Digital transmission to extend the range of the Local loop farther than would be possible using only In Telephony, the local loop (also referred to as a subscriber line) is the physical link or circuit that connects from the Demarcation point of the

IP telephony

A WiFi-based VoIP phone
A WiFi-based VoIP phone

Internet Protocol (IP) telephony (also known as Internet telephony) is a service based on Voice over IP (VoIP), a disruptive technology that is rapidly gaining ground against traditional telephone network technologies. Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used Voice-over-Internet protocol ( VoIP, vɔɪp is a protocol optimized for the transmission of voice through the Internet The Internet is a global system of interconnected Computer networks Voice-over-Internet protocol ( VoIP, vɔɪp is a protocol optimized for the transmission of voice through the Internet A disruptive technology or disruptive innovation is a term describing a technological innovation product or service that uses a "disruptive" strategy rather than In Japan and South Korea up to 10% of subscribers, as of January 2005, have switched to this digital telephone service. For a topic outline on this subject see List of basic Japan topics. South Korea, officially the Republic of Korea and often referred to as Korea ( Korean: 대한민국 tɛː A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing. Newsweek is an American weekly Newsmagazine published in New York City. " [1] As of 2006 many VoIP companies offer service to consumers and businesses. This is a list of commercial VoIP network providers arranged alphabetically with no restriction to Region. Consumers refers to individuals or households that use goods and services generated within the economy. A business (also called firm or an enterprise) is a legally recognized organizational entity designed to provide goods and/or services to

IP telephony uses a broadband Internet connection and IP Phones to transmit conversations as data packets. The term broadband can have different meanings in different contexts An IP phone uses Voice over IP technologies allowing telephone calls to be made over an IP network such as the internet instead of the ordinary PSTN system In Information technology, a packet is a formatted unit of Data carried by a Packet mode Computer network. In addition to replacing POTS(plain old telephone service), IP telephony is also competing with mobile phone networks by offering free or lower cost connections via WiFi hotspots. Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used A hotspot is a venue that offers Wi-Fi access to the Internet VoIP is also used on private wireless networks which may or may not have a connection to the outside telephone network.

IP telephony technology transforms many non-telephone electronics devices into unified communications devices which simulate telephone usage, such as adding telephone-like features to portable game devices, digital picture frames, or handheld GPS receivers, typically by incorporating a voice engine. A voice engine is a software subsystem for bidirectional audio communication typically used as part of a Telecommunications system to simulate a Telephone. When used on a personal computer, an IP telephone is referred to as a soft phone. In Computing, a softphone is a software program for making telephone calls over the Internet using a general purpose computer rather than using dedicated

Usage

By the end of 2006, there were a total of nearly 4 billion mobile and fixed line subscribers and over 1 billion Internet users worldwide. This included 1. 27 billion fixed line subscribers and 2. 68 billion mobile subscribers. [2]

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. Countries by alphabetical order A Afghanistan Albania Algeria A telephone company (or telco) provides Telecommunications services such as Telephony and Data communications Most of the largest telcos whatever Some of them are included in the following list. However, the list only includes facilities based providers and not companies which lease services from facilities based providers in order to serve their customers.

Patents

See also

References

Further reading

External links


The Open Directory Project ( ODP) also known as dmoz (from directory

Dictionary

telephone

-noun

  1. An electronic device used for two-way talking with other people (often shortened to phone).

-verb

  1. To call someone; to make someone's telephone ring using one's own telephone.
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