Telephone

Telephone

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The telephone colloquially
Colloquialism
A colloquialism is a word or phrase that is common in everyday, unconstrained conversation rather than in formal speech, academic writing, or paralinguistics. Dictionaries often display colloquial words and phrases with the abbreviation colloq. as an identifier...

 referred to as a phone, is a telecommunication
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

s device that transmits
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...

 and receives sounds, usually the human voice
Human voice
The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about 60 to 7000 Hz. The human voice is specifically that part of human sound production in which the vocal folds are the primary...

. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other. Developed around the 1870s by Alexander Graham Bell
Alexander Graham Bell
Alexander Graham Bell was an eminent scientist, inventor, engineer and innovator who is credited with inventing the first practical telephone....

 and others, the telephone has long been considered indispensable to businesses, households and governments, is now one of the most common appliances
Small appliance
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 in the United States of America...

 in the developed world. The word "telephone" has been adapted to many languages and is now recognized around the world.

All telephones have a microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...

 to speak into, an earphone 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
Telephone keypad
A telephone keypad is a keypad that appears on a "Touch Tone" telephone. It was standardised when the dual-tone multi-frequency system in the new push-button telephone was introduced in the 1960s, which gradually replaced the rotary dial....

 (or in older phones a telephone dial or no manual device) to enter the telephone number
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 orally to a switchboard operator...

 of the telephone to be called. The microphone and earphone are usually built into a handset
Handset
On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient...

 which is held up to the face to talk. The keypad may be part of the handset or of a base unit to which the handset would be connected. A landline
Landline
A landline was originally an overland telegraph wire, as opposed to an undersea cable. Currently, landline 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...

 telephone is connected by a pair of wires to the telephone network, while a mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

 or cell phone is portable and communicates with the telephone network by radio
Radio
Radio is the transmission of signals through free space 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...

. A cordless telephone
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...

 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
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...

 converts the sound waves to electrical signals and then these are sent through the telephone network
Telephone network
A telephone network is a telecommunications network used for telephone calls between two or more parties.There are a number of different types of telephone network:...

 to the other phone and there converted by an earphone back into sound waves. Telephones are a duplex
Duplex (telecommunications)
A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. The term multiplexing is used when describing communication between more than two parties or devices....

 communications medium, meaning they allow the people on both ends to talk simultaneously. The telephone network, consisting of a worldwide net of telephone line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...

s, fiberoptic cables, microwave transmission
Microwave transmission
Microwave transmission refers to the technology of transmitting information or power by the use of radio waves whose wavelengths are conveniently measured in small numbers of centimeters; these are called microwaves. This part of the radio spectrum ranges across frequencies of roughly...

, cellular network
Cellular network
A cellular network is a radio network distributed over land areas called 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...

s, communications satellite
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...

s, and undersea telephone cables connected by switching centers, allows any telephone in the world to communicate with any other. Each telephone line has an identifying number called its telephone number
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 orally to a switchboard operator...

. To initiate a telephone call
Telephone call
A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...

 the user enters the other telephone's number into a numeric keypad
Keypad
A keypad is a set of buttons arranged in a block or "pad" which usually bear digits, symbols and usually a complete set of alphabetical letters. If it mostly contains numbers then it can also be called a numeric keypad...

 on the phone. Graphic symbols used to designate telephone service or phone-related information in print, signage
Signage
Signage is any kind of visual graphics created to display information to a particular audience. This is typically manifested in the form of wayfinding information in places such as streets or inside/outside of buildings.-History:...

, and other media include (U+
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

2121), (U+
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

260E), (U+
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

260F), and (U+
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

2706).

Although originally designed for voice communication, the system has been adapted for data communication such as Telex
Telex
Telex may refer to:* Telex , , a communications network** Teleprinter, the device used on the above network* Telex , a Belgian pop group...

, Fax
Fax
Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

 and dial-up Internet communication.

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 influential invention
Invention
An invention is a novel 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...

s such as radio, television, the light bulb, and the 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 Manzetti
Innocenzo Vincenzo Bartolomeo Luigi Carlo Manzetti was an Italian inventor born in Aosta. Following his primary school studies 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.- Automaton :In 1849...

, Antonio Meucci
Antonio Meucci
Antonio Santi Giuseppe Meucci was an Italian inventor, a compatriot of revolutionary Giuseppe Garibaldi. He was best known for developing a voice communication apparatus which several sources credit as the first telephone....

, Johann Philipp Reis
Johann Philipp Reis
Johann Philipp Reis was a self-taught German scientist and inventor. In 1861, he constructed the first make-and-break telephone, today called the Reis telephone.- Early life and education :...

, Elisha Gray
Elisha Gray
Elisha Gray was an American electrical engineer who co-founded the Western Electric Manufacturing Company...

, Alexander Graham Bell
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 Edison
Thomas Alva Edison was an American inventor and businessman. He 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. In addition, he created the world’s first industrial...

, 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
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.The USPTO is based in Alexandria, Virginia,...

 (USPTO) in March 1876. 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 large number 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
Tivadar Puskás
Tivadar Puskás was a Hungarian inventor, telephone pioneer, and inventor of the telephone exchange He was also the founder of Telefon Hírmondó.-Biography:...

, quickly invented the telephone switchboard
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...

 in 1876, which allowed for the formation of telephone exchanges, and eventually networks.

Basic principles



A traditional landline
Landline
A landline was originally an overland telegraph wire, as opposed to an undersea cable. Currently, landline 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...

 telephone system, also known as "plain old telephone service
Plain old telephone service
Plain old telephone service is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in many parts of the world....

" (POTS), commonly handles both control and audio signals on the same twisted pair
Twisted pair
Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs...

 (C) of insulated wires: the telephone line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...

. The signaling equipment (see figure 1) consists of a bell, beeper, light or other device (A7) to alert the user to incoming calls, and number buttons or a rotary dial
Rotary dial
The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send 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. Almon Brown Strowger filed the first patent...

 (A4) to enter a telephone number
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 orally to a switchboard operator...

 for outgoing calls. Most of the expense of wire-lines are the wires, so having both received and sent voices on one pair of wires reduces the expense of wire-line service. Also, a twisted pair line rejects electromagnetic interference (EMI)
Electromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...

 and crosstalk better than a single wire or an untwisted pair. The strong microphone voice signal does not overpower the weaker incoming speaker signal with a sidetone
Sidetone
Sidetone is audible feedback to someone who is speaking. The term is most used in telecommunication contexts.-Telephony:In telephony, sidetone is the effect of sound that is picked up by the telephone's mouthpiece and in real-time introduced at a low level into the earpiece of the same handset,...

 because a hybrid coil
Hybrid coil
A hybrid coil is a transformer that has three windings, and which is designed to be configured as a circuit having four branches, that are conjugate in pairs....

 (A3) subtracts the microphone's signal from the signal sent to the local speaker. The junction box (B) arrests lightning (B2) and adjusts the line's resistance
Impedance matching
In electronics, impedance matching is the practice of designing the input impedance of an electrical load to maximize the power transfer and/or minimize reflections from the load....

 (B1) to maximize the signal power for the line's length. Telephones have similar adjustments for inside line lengths (A8). The wire's voltages are negative compared to earth, to reduce galvanic corrosion. Negative voltage attracts positive metal ions toward the wires.

Details of operation


The landline telephone contains a switchhook (A4) and an alerting device, usually a ringer (A7), that remains connected to the phone line whenever the phone is "on hook" (i.e. the switch (A4) is open), and other components which are connected when the phone is "off hook". The off-hook components include a transmitter (microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...

, A2), a receiver (speaker, A1), and other circuits for dialing, filtering (A3), and amplification.

A calling party
Calling party
The calling party is a person who initiates a telephone call over the public switched telephone network, usually by dialing a telephone number....

 wishing to speak to another party will pick up the telephone's handset
Handset
On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient...

, thereby operating a lever which closes the switchhook (A4), which powers the telephone by connecting the transmitter (microphone), receiver (speaker
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...

), and related audio components to the line. The off-hook circuitry has a low resistance (less than 300 ohm
Ohm
The ohm is the SI unit of electrical resistance, named after German physicist Georg Simon Ohm.- Definition :The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere,...

s) which causes a direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

 (DC), which comes down the line (C) from the telephone exchange
Telephone exchange
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 current, attaches a digit receiver circuit to the line, and sends a dial tone
Dial tone
A dial tone is a telephony signal used to indicate that the telephone exchange is working, has recognized an off-hook, and is ready to accept a call. The tone stops when the first numeral is dialed...

 to indicate readiness. On a modern push-button telephone
Push-button telephone
The push-button telephone was first invented in 1941, and is a telephone with push-buttons or keys, and which eventually replaced rotary dial telephones that were first used in 1891. The first push-button telephone was invented in the labs of Bell Telephone; however, these models were only...

, the caller then presses the number keys to send the telephone number of the called party
Called party
The called party is a person who answers a telephone call. The person who initiates a telephone call is the calling party....

. The keys control a tone generator circuit (not shown) that makes DTMF tones that the exchange receives. A rotary-dial telephone
Rotary dial
The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send 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. Almon Brown Strowger filed the first patent...

 uses pulse dialing
Pulse dialing
Pulse dialing, dial pulse, or loop disconnect dialing, also called rotary or decadic dialling in the United Kingdom , is pulsing in which a direct-current pulse train is produced by interrupting a steady signal according to a fixed or formatted code for each digit and at a standard pulse repetition...

, sending electrical pulses, that the exchange can count to get the telephone number (as of 2010 many exchanges were still equipped to handle pulse dialing). If the called party's line is available, the exchange sends an intermittent ringing signal (about 90 volts alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 (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 in use, the exchange returns a busy signal
Busy signal
A busy signal in telephony is an audible or visual signal to the calling party that indicates failure to complete the requested connection of that particular telephone call....

 to the calling party. However, if the called party's line is in use but has call waiting
Call waiting
Call waiting , in telephony, is a feature on some telephone networks. If a calling party places a call to a called party which is otherwise engaged, and the called party has the call waiting feature enabled, the called party is able to suspend the current telephone call and switch to the new...

 installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call.

The phone's ringer (A7) is connected to the line through a capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...

 (A6), a device which blocks direct current but passes alternating current. So, the phone draws no current when it is on hook (a DC voltage is continually connected to the line), but exchange circuitry (D2) can send an AC voltage down the line to ring for an incoming call. (When there is no exchange, telephones often have hand-cranked magneto
Magneto
A magneto is a type of electrical generator.Magneto may also refer to:* Magneto , permanent magnetic alternating current rotary generator* ignition magneto, magnetos on internal combustion engines...

s to make the ringing voltage.) When a landline phone is inactive or "on hook", the circuitry at the telephone exchange detects the absence of direct current and therefore "knows" that the phone is on hook (therefore, only AC current will go through) with only the alerting device electrically connected to the line. When a party initiates a call to this line, the exchange sends the ringing signal. When the called party picks up the handset, they actuate a double-circuit switchhook (not shown) which simultaneously disconnects the alerting device and connects the audio circuitry to the line. This, in turn, draws direct 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, direct current ceases in that line, signaling the exchange to disconnect the call
Telephone call
A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...

.

Calls to parties beyond the local exchange are carried over "trunk" lines which establish connections between exchanges. In modern telephone networks, fiber-optic cable
Fiber-optic communication
Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information...

 and digital technology
Digital Multiplex System
Digital Multiplex System is the name shared among several different telephony product lines from Nortel Networks for wireline and wireless operators...

 are often employed in such connections. Satellite technology
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...

 may be used for communication over very long distances.
In most landline telephones, the transmitter and receiver (microphone and speaker) are located in the handset
Handset
On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient...

, although in a speakerphone
Speakerphone
A speakerphone is a telephone with a microphone and loudspeaker provided separately from those in the handset. This device allows multiple persons to participate in a conversation...

 these components may be located in the base or in a separate enclosure. Powered by the line, the microphone (A2) produces a modulated electrical current which varies its frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

 and amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...

 in response to the sound
Sound
Sound is a mechanical 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.-Propagation of...

 waves arriving at its diaphragm
Diaphragm (acoustics)
In the field of acoustics, a diaphragm is a transducer intended to faithfully inter-convert mechanical motion and sound. It is commonly constructed of a thin membrane or sheet of various materials. The varying air pressure of the sound waves imparts vibrations onto the diaphragm which can then be...

. The resulting current is transmitted along the telephone line to the local exchange then on to the other phone (via the local exchange or via a larger network), where it passes through the coil
Voice coil
A voice coil is the coil of wire attached to the apex of a loudspeaker cone. It provides the motive force to the cone by the reaction of a magnetic field to the current passing through it...

 of the receiver (A3). The varying current in the coil produces a corresponding movement of the receiver's diaphragm, reproducing the original sound waves present at the transmitter.

Along with the microphone and speaker, additional circuitry is incorporated to prevent the incoming speaker signal and the outgoing microphone signal from interfering with each other. This is accomplished through a hybrid coil
Hybrid coil
A hybrid coil is a transformer that has three windings, and which is designed to be configured as a circuit having four branches, that are conjugate in pairs....

 (A3). The incoming audio signal passes through a resistor (A8) and the primary winding of the coil (A3) which passes it to the speaker (A1). Since the current path A8 - A3 has a far lower impedance than the microphone (A2), virtually all of the incoming signal passes through it and bypasses the microphone.

At the same time the DC voltage across the line causes a DC current which is split between the resistor-coil (A8-A3) branch and the microphone-coil (A2-A3) branch. The DC current through the resistor-coil branch has no effect on the incoming audio signal. But the DC current passing through the microphone is turned into AC current (in response to voice sounds) which then passes through only the upper branch of the coil's (A3) primary winding, which has far fewer turns than the lower primary winding. This causes a small portion of the microphone output to be fed back to the speaker, while the rest of the AC current goes out through the phone line.

A Lineman's handset
Lineman's handset
A lineman's handset is a special type of telephone used by technicians for installing and testing local loop telephone lines. It is also called a test set, butt set, or buttinski.-Components:...

 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
    Innocenzo Manzetti
    Innocenzo Vincenzo Bartolomeo Luigi Carlo Manzetti was an Italian inventor born in Aosta. Following his primary school studies 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.- Automaton :In 1849...

     first mooted the idea of a “speaking telegraph” (telephone).
  • 26 August 1854 — Charles Bourseul
    Charles Bourseul
    Charles Bourseul was a pioneer in development of the "make and break" telephone about 20 years before Bell made a practical telephone....

     published an article in a magazine L'Illustration
    L'Illustration
    L'Illustration was a weekly French newspaper published in Paris. It was founded by Edouard Charton; the first issue was published on March 4, 1843....

     (Paris) : "Transmission électrique de la parole" [electric transmission of speech].
  • 26 October 1861 — Johann Philipp Reis
    Johann Philipp Reis
    Johann Philipp Reis was a self-taught German scientist and inventor. In 1861, he constructed the first make-and-break telephone, today called the Reis telephone.- Early life and education :...

     (1834–1874) publicly demonstrated the Reis telephone
    Reis telephone
    The Reis telephone, was an invention by Philipp Reis inspired by a French article in 1854 on how to create microphone-like devices...

     before the Physical Society of Frankfurt.
  • 22 August 1865, La Feuille d'Aoste reported “It is rumored that English technicians to whom Mr. Manzetti
    Innocenzo Manzetti
    Innocenzo Vincenzo Bartolomeo Luigi Carlo Manzetti was an Italian inventor born in Aosta. Following his primary school studies 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.- Automaton :In 1849...

     illustrated his method for transmitting spoken words on the telegraph wire intend to apply said invention in England on several private telegraph lines", however telephones were not demonstrated there until after Alexander Graham Bell received his patent in the United States of America in 1876.
  • 28 December 1871 — Antonio Meucci
    Antonio Meucci
    Antonio Santi Giuseppe Meucci was an Italian inventor, a compatriot of revolutionary Giuseppe Garibaldi. He was best known for developing a voice communication apparatus which several sources credit as the first telephone....

     files a patent caveat
    Patent caveat
    A patent caveat was a legal document filed with the United States Patent Office. Caveats were instituted by the US Patent Act of 1836, but were discontinued in 1909. A caveat was like a patent application with a description of an invention and drawings, but without claims. It was an official...

     (No. 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 does not renew it again, and 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
    Patent caveat
    A patent caveat was a legal document filed with the United States Patent Office. Caveats were instituted by the US Patent Act of 1836, but were discontinued in 1909. A caveat was like a patent application with a description of an invention and drawings, but without claims. It was an official...

     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
Induction coil
An induction coil or "spark coil" is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current supply...

 which was an impedance matching
Impedance matching
In electronics, impedance matching is the practice of designing the input impedance of an electrical load to maximize the power transfer and/or minimize reflections from the load....

 transformer to make it compatible with 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
Outside plant
In telecommunication, the term outside plant has the following meanings:*In civilian telecommunications, outside plant refers to all of the physical cabling and supporting infrastructure , and any associated hardware located between a demarcation point in a switching facility and a demarcation...

 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
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...

 over the same wires that carried the voice signals.

Early telephones used a single wire for the subscriber's line, with ground return
Single wire earth return
Single wire earth return or single wire ground return is a single-wire transmission line for supplying single-phase electrical power from an electrical grid to remote areas at low cost...

 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
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...

 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
Western Union
The Western Union Company is a financial services and communications company based in the United States. Its North American headquarters is in Englewood, Colorado. Up until 2006, Western Union was the best-known U.S...

, already using telegraph exchanges, quickly extended the principle to its telephones in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 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
Switchboard operator
In the early days of telephony, through roughly the 1960s, companies used manual telephone switchboards and switchboard operators connected each call by inserting a pair of phone plugs into the appropriate jacks. Each pair of plugs was part of a cord circuit with a switch associated that let the...

, by whistling
Whistling
Human whistling is the production of sound by means of carefully controlling a stream of air flowing through a small hole. Whistling can be achieved by creating a small opening with one's lips and then blowing or sucking air through the hole...

 into the transmitter. Exchange operation soon resulted in telephones being equipped with a bell in a ringer box
Ringer box
The ringer box is an external phone ringer housed in a bell box or subscriber set, and was used with most early desk stand type phones including the candlestick telephones, and the Western Electric model 102 and 202 telephones, which were too small to hold a ringer or other needed electrical parts...

, first operated over a second wire, and later over the same wire, but with a condenser (capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...

) in series with the bell coil to allow the AC
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 ringer signal through while still blocking DC
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

 (keeping the phone "on hook"). Telephones connected to the earliest Strowger automatic exchanges
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...

 had seven wires, one for the knife switch, one for each telegraph key
Telegraph key
Telegraph key is a general term for any switching device used primarily to send Morse code. Similar keys are used for all forms of manual telegraphy, such as in electrical telegraph and radio telegraphy.- Types of keys :...

, one for the bell, one for the push-button and two for speaking. Large wall telephones in the early 20th century usually incorporated the bell, and separate bell boxes for desk phones dwindled away in the middle of the century.

Rural and other telephones that were not on a common battery exchange had a magneto
Magneto (electrical)
A magneto is an electrical generator that uses permanent magnets to produce alternating current.Magnetos adapted to produce pulses of high voltage are used in the ignition systems of some gasoline-powered internal combustion engines to provide power to the spark plugs...

 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 or "ringer box
Ringer box
The ringer box is an external phone ringer housed in a bell box or subscriber set, and was used with most early desk stand type phones including the candlestick telephones, and the Western Electric model 102 and 202 telephones, which were too small to hold a ringer or other needed electrical parts...

". 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, now called a handset
Handset
On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient...

, 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 pair
Twisted pair
Twisted pair cabling is a type of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs...

s and, for long distance telephones, four-wire circuit
Four-wire circuit
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 only by one path and in the other direction by the other path...

s. Users at the beginning of the 20th century did not place long distance call
Long Distance Call
"Long Distance Call" is an episode of the American television anthology series The Twilight Zone.-Synopsis:A boy communicates with his father's European-immigrant mother, who had recently died, using a toy telephone that she gave him on his birthday before her passing. The boy, Billy, runs out in...

s from their own telephones but made an appointment to use a special sound proofed long distance telephone booth
Telephone booth
A telephone booth, telephone kiosk, telephone call box or telephone box is a small structure furnished with a payphone and designed for a telephone user's convenience. In the USA, Canada and Australia, "telephone booth" is used, while in the UK and the rest of the Commonwealth it is a "telephone...

 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
Model 102 telephone
The Model 102 telephone was Western Electric's first widely distributed telephone set to feature the transmitter and receiver in a common handset. Prior models had been of the "candlestick" type, which featured a transmitter fixed to the base, and a receiver held to the ear...

. A carbon granule transmitter
Carbon microphone
The carbon microphone, also known as a carbon button microphone or a carbon transmitter, is a sound-to-electrical signal transducer consisting of two metal plates separated by granules of carbon. One plate faces outward and acts as a diaphragm...

 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
Rotary dial
The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send 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. Almon Brown Strowger filed the first patent...

 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
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...

 (PSTN) has gradually evolved towards digital telephony
Telephony
In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....

 which has improved the capacity and quality of the network. End-to-end analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...

 telephone networks were first modified in the early 1960s by upgrading transmission networks with T1
Digital Signal 1
Digital signal 1 is a T-carrier signaling scheme devised by Bell Labs. DS1 is a widely used standard in telecommunications in North America and Japan to transmit voice and data between devices. E1 is used in place of T1 outside North America, Japan, and South Korea...

 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
Wideband voice
Wideband Voice refers to the use of Wideband Codecs in Digital telephony. Wideband Codecs use higher sampling rates than Narrowband Codecs or utilize embedded sub-band coding techniques to effectively increase the bandwidth of the baseband voice, from the traditional 200 Hz to 3.5 kHz...

 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
Sonet
Sonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...

 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
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...

 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
Serving area interface
The serving area interface or service area interface often called B-box, cross-connect box, cross box, ped , or access point is an outdoor telecommunications cabinet usually mounted on the ground on cable right-of-ways, but sometimes also on telephone poles...

 (SAI), central office (CO), or other aggregation point. Digital loop carrier
Digital loop carrier
A digital loop carrier is a system which uses digital transmission to extend the range of the local loop farther than would be possible using only twisted pair copper wires...

s (DLC) place the digital network ever closer to the customer premises, relegating the analog local loop
Local loop
In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider's network...

 to legacy status.

IP telephony



Internet Protocol (IP) telephony (also known as Voice over Internet Protocol, VoIP), is a disruptive technology
Disruptive technology
A disruptive technology or disruptive innovation is an innovation that helps create a new market and value network, and eventually goes on to disrupt an existing market and value network , displacing an earlier technology there...

 that is rapidly gaining ground against traditional telephone network technologies. As of January 2005, up to 10% of telephone subscribers in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 and South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...

 have switched to this digital telephone service. A January 2005 Newsweek
Newsweek
Newsweek is an American weekly news magazine published in New York City. It is distributed throughout the United States and internationally. It is the second-largest news weekly magazine in the U.S., having trailed Time in circulation and advertising revenue for most of its existence...

 article suggested that Internet telephony may be "the next big thing." As of 2006 many VoIP companies offer service to consumer
Consumer
Consumer is a broad label for any individuals or households that use goods generated within the economy. The concept of a consumer occurs in different contexts, so that the usage and significance of the term may vary.-Economics and marketing:...

s and business
Business
A business is an organization engaged in the trade of goods, services, or both to consumers. Businesses are predominant in capitalist economies, where most of them are privately owned and administered to earn profit to increase the wealth of their owners. Businesses may also be not-for-profit...

es.

IP telephony uses an Internet connection and hardware IP Phone
IP Phone
A VoIP 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. Calls can traverse the Internet, or a private IP network such as that of a company...

s or softphone
Softphone
A softphone is a software program for making telephone calls over the Internet using a general purpose computer, rather than using dedicated hardware. Often a softphone is designed to behave like a traditional telephone, sometimes appearing as an image of a phone, with a display panel and buttons...

s installed on personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

s 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
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

 services by offering free or lower cost connections via WiFi
WIFI
WIFI is a radio station broadcasting a brokered format. Licensed to Florence, New Jersey, USA, the station is currently operated by Florence Broadcasting Partners, LLC.This station was previously owned by Real Life Broadcasting...

 hotspots
Hotspot (Wi-Fi)
A hotspot is a site that offers Internet access over a wireless local area network through the use of a router connected to a link to an Internet service provider...

. 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
Uninterruptible power supply
An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...

 or other emergency power source, the phone will cease to function during a power outage
Power outage
A power outage is a short- or long-term loss of the electric power to an area.There are many causes of power failures in an electricity network...

 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.

Telephone operating companies



In some countries, many telephone operating companies (commonly abbreviated to telco
Telephone company
A telephone company is a service provider of telecommunications services such as telephony and data communications access. Many were at one time nationalized or state-regulated monopolies...

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
    Mobile phone
    A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

    ) -- Martin Cooper et al. (Motorola)

Further reading

  • Sobel, Robert
    Robert Sobel
    Robert Sobel was an American professor of history at Hofstra University, and a well-known and prolific writer of business histories.- Biography :...

    (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