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Telephone

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The telephone or phone is a telecommunications device that transmits speech by means of electric signals. Generally attributed to the inventor Alexander Graham Bell, the first was built in Boston, Massachusetts, in 1876. However, an Italian inventor Antonio Meucci is said to have invented the device in 1849, and in September 2001, Meucci was officially credited by the US Congress with the invention of the telephone, instead of Alexander Graham Bell. According to other Sources Philip Reis invented it in 1860, but due to a false translation of the German word "Telephon" his invention was considered only the predecessor of Bell's one.

TelephoneEnlarge

Telephone

Table of contents
1 History
2 Land-fixed phone systems
3 Wireless phone systems
4 Telephone equipment manufacturers
5 Telephone equipment research labs
6 Telephone operating companies
7 Related articles

History

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. There was a lot of money involved, particularly in the Bell Telephone companies, and the aggressive defense of the Bell patents resulted in much confusion. Additionally, the earliest investigators preferred publication in the popular press and demonstrating to investors to scientific publication and demonstrating to fellow scientists.

It is important to note that there is no "inventor of the telephone." The modern telephone is the result of work done by many hands, all worthy of recognition of their addition to the field.

See Timeline of the telephone for a chronological survey of the telephone's invention and development.

See Invention of the telephone for a discussion of each of the critical technologies and their inventors.

The text below draws heavily on Heros of the Telegraph by John Munro, Project Gutenberg edition [1].

Non-electric 'telephones'

The very early constructions of the telephone was based on sound transportation through air or other physical media rather than generated electric signals from speech. According to a letter in the Peking Gazette, in 968, the Chinese inventor Kung-Foo-Whing invented the thumtsein, which probably transported the speech through pipes. Even the early telephone-like inventions transported the sound through pipes. The Lovers telegraph or String telephone has also been known for centuries connecting two diaphrams with string or wire which transmits the sound from one to the other by vibrations along the string and not through electrical current.

Electro-magnetic transmitters

Antonio Meucci

It may be argued that telephone was invented around 1860 by Antonio Meucci who called it teletrophone.

From [1] Despite a public statement by the then Secretary of State that "there exists sufficient proof to give priority to Meucci in the invention of the telephone," and despite the fact that the United States initiated prosecution for fraud against Bell's patent, the trial was postponed from year to year until, at the death of Meucci in 1896, the case was dropped.

The first American demonstration of Meucci's invention took place in 1860, and had a description of it published in New York's Italian language newspaper. Meucci invented a paired electro-magnetic transmitter and receiver, where the motion of a diaphram modulated a signal in a coil by moving an electromagnet. This resulted in a good fidelity, but a very weak signal. Meucci is also credited with the early invention of the anti-sidetone circuit, and of inductive loading of telephone wires to increase long-distance signals. Unfortunately, serious burns, lack of English and poor business abilities resulted in Meucci failing to develop his inventions commercially in America. Meucci demonstrated some sort of instrument in 1849 in Havana, Cuba, but the evidence is unclear if this was an electric telephone or a variant on the string telephone using wires.

Make-Break transmitters

Charles Bourseul

In 1854, M. Charles Bourseul, a French telegraphist, had conceived a plan for conveying sounds and even speech by electricity.

'Suppose,' he explained, 'that a man speaks near a movable disc sufficiently flexible to lose none of the vibrations of the voice; that this disc alternately makes and breaks the currents from a battery: you may have at a distance another disc which will simultaneously execute the same vibrations.... It is certain that, in a more or less distant future, speech will be transmitted by electricity. I have made experiments in this direction; they are delicate and demand time and patience, but the approximations obtained promise a favourable result.'

Bourseul deserves the credit of being perhaps the first to devise an electric telephone and try to make it. It fell to Johhan Reis to be the first to demonstrate a make-break instrument.

Johann Philipp Reis

In 1860 Johann Philipp Reis produced a device which could transmit musical notes, and even a lisping word or two. The Reis transmitter was a make-break transmitter. That is, a needle attached to a diaphram was alternately pressed against, and released from a contact as the sound moved the diaphram. This make-or-break signaling was able to transmit tones, and some vowels, but since it did not follow the analog shape of the sound wave (the contact was pure digital, on or off) it could not transmit consonants, or complex sounds. The Reis transmitter was very difficult to operate, since the relative position of the needle and the contact were critical to the device's operation at all. This can be called a "telephone", since it did transmit sounds over distance, but is hardly a telephone in the modern sense, as it failed to transmit a good copy of any supplied sound. Reis' invention is best known then as the "musical telephone".

Cromwell Varley

Around 1870 Mr. Cromwell Fleetwood Varley, F.R.S., a well-known English electrician, patented a number of variations on the audio telegraph based on Reis work. He never claimed or produced a device capable of transmitting speech, only pure sounds.

Poul la Cour

Around 1874 Poul la Cour, a Danish inventor, experimented with audio telegraphs on a line of telegraph between Copenhagen and Fredericia in Jutland. In this a vibrating tuning-fork interrupted the current, which, after traversing the line, passed through an electromagnet, and attracted the limbs of another fork, making it strike a note like the transmitting fork. Moreover, the hums were made to record themselves on paper by turning the electromagnetic receiver into a relay, which actuated a Morse printer by means of a local battery. Again, la Cour made no claims of transmitting voice, only pure tones.

Elisha Gray

Mr. Elisha Gray, of Chicago also devised a tone telegraph of this kind about the same time as Herr La Cour. In this apparatus a vibrating steel tongue interrupted the current, which at the other end of the line passed through the electromagnet and vibrated a band or tongue of iron near its poles. Gray's 'harmonic telegraph,' with the vibrating tongues or reeds, was afterwards introduced on the lines of the Western Union Telegraph Company in America. As more than one set of vibrations--that is to say, more than one note--can be sent over the same wire simultaneously, it is utilised as a 'multiplex' or many-ply telegraph, conveying several messages through the same wire at once; and these can either be interpreted by the sound, or the marks drawn on a ribbon of travelling paper by a Morse recorder.

Gray's harmonic telegraph apparatus follows in the track of Reis and Bourseul--that is to say, the interruption of the current by a vibrating contact.

Gray recognized the lack of fidelity of the make-break transmitter, and reasoned by analogy with the lovers telegraph that if the current could be made to model more closely the movements of the diaphram rather than simply turning the circuit on and off, a greater fidelity might be achieved. Gray built and patented a liquid microphone, where a needle was placed just barely in contact with a liquid conductor, and as the diaphram vibrated, the needle dipped more-or-less into the liquid, resulting in more-or-less current passing to the receiver. Bell used a Gray liquid transmitter for many of his early public demonstrations. The liquid transmitter had the problem that the waves formed on the surface of the liquid resulted in interference.

Carbon Grain transmitter

Thomas Edison

Thomas Alva Edison took the next step in developing telephonic fidelity with his invention of the carbon grain transmitter. Edison discovered that carbon grains, squeezed between two metal plates had a resistance that was related to the pressure, thus, the grains could vary their resistance as the plates moved in response to sound waves, and reproduce sound with good fidelity, without the problems associated with a liquid contact. This style of transmitter remained standard in telephony until the 1980's, and is still produced.

Bell's invention and claims

Alexander Graham Bell is commonly credited as the inventor of the telephone. The classic story of his crying out "Watson, come here! I need you!" is a part of the common western mythos.

Bell's background

As Professor of Vocal Physiology in the University of Boston, Bell was engaged in training teachers in the art of instructing deaf mutes how to speak, and experimented with the Leon Scott phonautograph in recording the vibrations of speech. This apparatus consists essentially of a thin membrane vibrated by the voice and carrying a light stylus, which traces an undulatory line on a plate of smoked glass. The line is a graphic representation of the vibrations of the membrane and the waves of sound in the air.

This background prepared him for work with sound and electricity. He began his researches in 1874 with a musical telegraph, in which he employed a make-break circuit driven by a vibrating iron reed which created interrupted current to vibrate the receiver, which consisted of an electro-magnet causing an iron reed or tongue to vibrate, exactly the same as Bourseul, Reis and Gray. One day it was found that a reed failed to respond to the intermittent current. Mr. Bell desired his assistant, who was at the other end of the line, to pluck the reed, thinking it had stuck to the pole of the magnet. Mr. Watson complied, and to his astonishment Bell observed that the corresponding reed at his end of the line there upon began to vibrate and emit the same note, although there was no interrupted current to make it. A few experiments soon showed that his reed had been set in vibration by the magneto-electric currents induced in the line by the mere motion of the distant reed in the neighbourhood of its magnet. This discovery led him to discard the battery current altogether and rely upon the magneto-induction currents of the reeds themselves. Moreover, it occurred to him that, since the circuit was never broken, all the complex vibrations of speech might be converted into sympathetic currents, which in turn would reproduce the speech at a distance.

Bell, with his assistant Watson discovered that the movements of the reed alone in a magnetic field could transmit the modulations of the sound. Working from the analogy of the phonautograph, Bell devised a receiver, consisting of a stretched diaphragm or drum of goldbeater's skin with an armature of magnetised iron attached to its middle, and free to vibrate in front of the pole of an electromagnet in circuit with the line.

Bell's success

This apparatus was completed on June 2, 1875, and the same day he succeeded in transmitting sounds and audible signals by magneto-electric currents and without the aid of a battery. On July 1, 1875, he instructed his assistant to make a second membrane-receiver which could be used with the first, and a few days later they were tried together, one at each end of the line, which ran from a room in the inventor's house at Boston to the cellar underneath. Bell, in the room, held one instrument in his hands, while Watson in the cellar listened at the other. The inventor spoke into his instrument, 'Do you understand what I say?' and we can imagine his delight when Mr. Watson rushed into the room, under the influence of his excitement, and answered,'Yes.' However, the first successful bi-directional telephone call by Bell wasn't made until March 10, 1876 when Bell spoke into his device, "Mr. Watson, come here, I want to see you." and Watson answered. Thus, by 1875, Bell had re-invented Meucci's electro-magnetic sound powered transmitter. The first long distance telephone call was made on August 10, 1876 by Bell from the family homestead in Brantford, Ontario to his assistant located in Paris, Ontario, some 16 km (10 mi.) distant.

A finished instrument was then made, having a transmitter formed of a double electromagnet, in front of which a membrane, stretched on a ring, carried an oblong piece of soft iron cemented to its middle. A mouthpiece before the diaphragm directed the sounds upon it, and as it vibrated with them, the soft iron 'armature' induced corresponding currents in the cells of the electromagnet. These currents after traversing the line were passed through the receiver, which consisted of a tubular electromagnet, having one end partially closed by a thin circular disc of soft iron fixed at one point to the end of the tube. This receiver bore a resemblance to a cylindrical metal box with thick sides, having a thin iron lid fastened to its mouth by a single screw. When the undulatory current passed through the coil of this magnet, the disc, or armature-lid, was put into vibration and the sounds evolved from it.

The primitive telephone was rapidly improved, the double electromagnet being replaced by a single bar magnet having a small coil or bobbin of fine wire surrounding one pole, in front of which a thin disc of ferrotype is fixed in a circular mouthpiece, and serves as a combined membrane and armature. On speaking into the mouthpiece, the iron diaphragm vibrates with the voice in the magnetic field of the pole, and thereby excites the undulatory currents in the coil, which, after travelling through the wire to the distant place, are received in an identical apparatus. [This form was patented January 30, 1877.] In traversing the coil of the latter they reinforce or weaken the magnetism of the pole, and thus make the disc armature vibrate so as to give out a mimesis of the original voice. The sounds are small and elfin, a minim of speech, and only to be heard when the ear is close to the mouthpiece, but they are remarkably distinct, and, in spite of a disguising twang, due to the fundamental note of the disc itself, it is easy to recognise the speaker.

Public demonstrations

Earliest public exhibitions of Bell's telephone

The apparatus was exhibited at the Centennial Exhibition, Philadelphia, in 1876, and at the meeting of the British Association in Glasgow, during the autumn of that year, Sir William Thomson revealed its existence to the European public. In describing his visit to the Exhibition, he went on to say: 'In the Canadian department I heard, "To be or not to be . . . there's the rub," through an electric wire; but, scorning monosyllables, the electric articulation rose to higher flights, and gave me passages taken at random from the New York newspapers: "s.s. Cox has arrived" (I failed to make out the s.s. Cox); "The City of New York," "Senator Morton," "The Senate has resolved to print a thousand extra copies," "The Americans in London have resolved to celebrate the coming Fourth of July!" All this my own ears heard spoken to me with unmistakable distinctness by the then circular disc armature of just such another little electro-magnet as this I hold in my hand.'

To hear the immortal words of Shakespeare uttered by the small inanimate voice which had been given to the world must indeed have been a rare delight to the ardent soul of the great electrician.

The surprise created among the public at large by this unexpected communication will be readily remembered. Except one or two inventors, nobody had ever dreamed of a telegraph that could actually speak, any more than they had ever fancied one that could see or feel; and imagination grew busy in picturing the outcome of it. Since it was practically equivalent to a limitless extension of the vocal powers, the ingenious journalist soon conjured up an infinity of uses for the telephone, and hailed the approaching time when ocean-parted friends would be able to whisper to one another under the roaring billows of the Atlantic. Curiosity, however, was not fully satisfied until Professor Bell, the inventor of the instrument, himself showed it to British audiences, and received the enthusiastic applause of his admiring countrymen.

Later public demonstrations
The later form based on Gray's liquid transmitter was publicly exhibited on May 4, 1877 at a lecture given by Professor Bell in the Boston Music Hall. 'Going to the small telephone box with its slender wire attachments,' says a report, 'Mr. Bell coolly asked, as though addressing some one in an adjoining room, "Mr. Watson, are you ready!" Mr. Watson, five miles away in Somerville, promptly answered in the affirmative, and soon was heard a voice singing "America."....Going to another instrument, connected by wire with Providence, forty-three miles distant, Mr. Bell listened a moment, and said, "Signor Brignolli, who is assisting at a concert in Providence Music Hall, will now sing for us." In a moment the cadence of the tenor's voice rose and fell, the sound being faint, sometimes lost, and then again audible. Later, a cornet solo played in Somerville was very distinctly heard. Still later, a three-part song floated over the wire from the Somerville terminus, and Mr. Bell amused his audience exceedingly by exclaiming, "I will switch off the song from one part of the room to another, so that all can hear." At a subsequent lecture in Salem, Massachusetts, communication was established with Boston, eighteen miles distant, and Mr. Watson at the latter place sang "Auld Lang Syne," the National Anthem, and "Hail Columbia," while the audience at Salem joined in the chorus.'

Summary of Bell's achievements

Bell adopted Gray, and later Edison's resistive transmitters and adapted switching plug boards developed for telegraphy by Western Union. It would be inappropriate to minimize Bell's contribution to the development of telephony. Additionally, Bell succeeded where others failed to assemble a commercially viable telephone system. It can be argued that Bell invented the telephone company.

Later developments

To do: add carbon grain transmitter, magneto, central, common battery, etc.

Bell had overcome the difficulty which baffled Reis, and succeeded in making the undulations of the current fit the vibrations of the voice as a glove will fit the hand. But the articulation, though distinct, was feeble, and it remained for Edison, by inventing the carbon transmitter, and Hughes, by discovering the microphone, to render the telephone the useful and widespread apparatus which we see it now.

Misc

The Ericofon was a very futuristic handset when it was introduced in 1956Enlarge

The Ericofon was a very futuristic handset when it was introduced in 1956

The modern handset came into existence when a swedish lineman tied a microphone and earphone to a stick so he could keep a hand free. The folding portable phone was an intentional copy of the fictional futuristic communicators used in the television show Star Trek.

The history of additional inventions and improvements of the electrical telephone includes the carbon microphone (later replaced by the electret microphone now used in almost all telephone transmitters), the manual switchboard, the rotary dial, the automatic telephone exchange, the computerized telephone switch, Touch Tone® dialing (DTMF), the digitization of sound using different coding techniques including pulse code modulation or PCM (which is also used for .WAV files and compact discs).

Newer systems include IP telephony, ISDN, DSL, cell phone (mobile) systems, digital cell phone systems, cordless telephones and the third generation cell phone systems that promise to allow high-speed packet data transfer.

The industry divided into telephone equipment manufacturers and telephone network operators (telcos). Operating companies often hold a national monopoly. In the United States, the Bell System was vertically integrated. It fully or partially owned the telephone companies that provided service to about 80% of the telephones in the country and also owned Western Electric, which manufactured or purchased virtually all the equipment and supplies used by the local telephone companies. The Bell System divested itself of the local telephone companies in 1984 in order to settle an antitrust suit brought against it by the United States Department of Justice.

The first transatlantic telephone call was between New York City and London and occurred on January 7, 1927.

Land-fixed phone systems

Wired telephony

The network that connects most phones together is known as the Public Switched Telephone Network (PSTN).

Fixed phone lines are usually copper wirelines which form a circuit between the subscriber and a subscriber-line interface. The Single Line Interface (SLI) is nondescript street furniture, usually a box on the ground, or a silver can on a telephone pole. The SLI provides dial-tone, and converts voice and dialed numbers to digital signals, which are sent on a few wires to the exchange. SLIs were invented so that central offices could be smaller, thus less expensive, while giving better service. Some recent installations may use optical fiber to connect an SLI to the exchange. Some old installations may connect subscribers directly to an exchange without using SLIs.

An analog phone's twisted pair is self-contained, self-testing and designed to fail safely. It typically modulates incoming and outgoing conversations on the same pair of wires, and biases the lines at 48 volts DC to power the telephone. The power is provided from multiply-redundant power systems at the exchange—most phones will continue to work in a power-failure. Further, the dial-tone is presented only when the SLIs, and exchange's computer believe the network is up.

An analog line uses frequencies of 0-3.5 kHz, with frequencies higher than this filtered at the SLI before it is converted to digital samples. The analog speech signals are carried over the digital backbone network as a stream of digitally encoded samples at a sample rate of 8 kHz (8,000 numeric samples representing sound-pressure per second). The frequences on the copper above 4 kHz can be utilized for DSL connections.

A line is a single voice communications circuit between the subscriber and the central switching office. A trunk is a single circuit between an SLI or central offices and may be analog or digital and is transmitted via copper, microwave, or fiber optics. A trunk group is a grouping of identical trunk circuits between two specific central offices.

Automatic telephone systems generally use numeric addresses, more commonly known as telephone numbers. The addressing system often distinguishes local, long-distance and international calls. Local calls are initiated by dialling the local number. A long-distance number is indicated by a long-distance prefix (ITU-T recommends "0") followed by area code and a number local to that area. International phone calls require an international prefix (the ITU-T recommends "00") followed by area code and local number. US and Canadian phone systems use "1" as the long distance prefix and "011" for international prefix. See country calling codes for access codes to international telephone services.

Larger companies and organizations often employ a private branch exchange (PBX; also called a private automatic branch exchange or PABX). This is a telephone switch that defines its own local phone number range, which is commonly embedded in a public local phone number range. Some of the largest companies now even have their own internal telephone networks across the country, or even throughout the world, with limited gateways into the PSTN.

Most PSTN systems use analog communication between individual phones and the local switch. If digital communication is used for an individual phone, the system used is usually Integrated Services Digital Network (ISDN).

Between switches in the PSTN, most signalling is now digital using Signalling System 7 (SS7).

Fixed Cordless telephones

Cordless handsetEnlarge

Cordless handset

Cordless telephones consist of a base unit that connects to the land-line system and also communicates with remote handsets by low power radio. This permits use of the handset from any location within range of the base. Because of the power required to transmit to the handset, the base station is powered with an AC adapter. Thus, cordless phones typically do not function during power outages. Initially, cordless phones used the 1.7 MHz range to communicate between base and handset. Because of quality and range problems, these units were soon superseded by systems that used frequency modulation in higher frequency ranges (49 MHz, 900 MHz, 2.4 GHz, and 5.8 GHz). 2.4 GHz cordless phones can interfere with certain wireless LAN protocols (802.11b/g) due to the usage of the same frequencies. Due to crowding on the 2.4 GHz band, several "channels" are utilized in an attempt to guard against degradation in the quality of the voice signal. The range of modern cordless phones is normally on the order of a few hundred yards.

Wireless phone systems

They are the satellite and mobile systems.

Nikola Tesla

On the opening of the telephone exchange in Budapest, 1881, Nikola Tesla became the chief electrician to the telephone company (engineer to the Yugoslaviann government and the country's first telephone system). There Tesla invented a device he called a telephone repeater or amplifier. The device could act as a loud speaker. The invention was never patented nor released publicly. It was eventually used to detect signals in wireless transmission experiments. The apparatus developed in these experiments were precursors to the modern wireless telephone.

The apparatus also involved the following:

Mobile phone

Modern mobile phone systems are cell-structured. Radio is used to communicate between a handset and a cell-site. Communication between cell-sites and the public switched telephone network can be by digital microwave radio, digital optic fiber or digital copper land lines communicating with a telephone exchange.

When a handset gets too far from a cell-site, a computer system commands the handset and a closer cell-site to take up the communications on a different channel without interrupting the call.

Modern mobile phones use cells because radio frequencies are a limited, shared resource. Cell-sites and handsets have low power transmitters so that a limited number of radio frequencies can be reused by many callers with less interference. An incidental benefit is that the batteries in the handsets need less power.

Standards

There are many standards for common carrier wireless telephony, often with incompatible standards used in the same nation:

Telephone equipment manufacturers

Several manufacturers build telephones of all kinds. Some of these are:

Telephone equipment research labs

Bell Labs is a noted telephone equipment research laboratory, amongst its other research fields.

Telephone operating companies

In some countries, many telephone operating companies (commonly abbreviated to telco) are in competition to provide telephony services. Some of them include those in the following list. However, the list only includes providers of copper wires from the exchange to the user, not those who only supply "Voice over IP" or only transport voice signals between exchanges.

See: List of telephone operating companies.

Related articles

Telephone equipment

610 (telephone), 431A, Answering machine, Ericofon, Modem, Payphone, Pen Register, Phone, Photophone, Switchboard, Telecommunications Device for the Deaf (TDD or TTY), Teletype, Telex, Telautograph, Telegraph

Telephone technology

1-4-7-1, ADSL, AIOD leads, ANAC, ANI, Assistive Technology, Automatic redial, Call forwarding, Caller ID, Camp-on busy signal, Computer telephony integration (CTI), Customer premises equipment (CPE), Dial Tone, Digital subscriber line, Direct dial, Direct distance dialing, Dual tone multi frequency (DTMF), Telephone feature code (* code), Party line, Plain Old Telephone Service (POTS), Ringing signal, Videotex, Voice over Internet Protocol (VOIP),

Telephone system, organization and structure

Area code, Office code, Basic exchange telecommunications radio service, Bell System, Call center, Competitive local exchange company (CLEC), Foreign exchange service, Incumbent local exchange company (ILEC), Local exchange company (LEC), Public Switched Telephone Network (PSTN), Regional Bell operating company (RBOC), Post office, Private line,

Telephone hacking and exploitation

Blue box, Bomb threat, Crank (or prank) call, Demon dialing, (Phone) phreaking, War dialing,

Telephone terminology

Call originator, Call waiting, Called party, Caller, Calling party, COCOT, Deaf, Emergency telephone number, End instrument, Fax, Help desk, Hunt Group, Infrastructure, Interactive voice response (IVR), Line, Local loop, Long-distance operator, Operator assistance, Person-to-person, Red telephone box, Red Box, Ringer equivalency number (REN), Ringing signal, Rural radio service, Smartphone, Station-to-station, TAPI, Telemarketing, Telephone booth, Telephone call, Telephone card, Telephone directory, Telephone exchange, Telephone tapping, Telemarketing, Trap and trace, TWX, Vertical service code, Voicemail, Western Union, Wide Area Telephone Service (WATS), WATS line, Wireless network, Wi-Fi, Zenith number

See also:

US-specific

Federal Standard 1037C-Glossary of telephony terms, Federal Regulations - Part 68, Modification of Final Judgment, Local access and transport area (LATA), Local exchange carrier, Interexchange carrier, Regional Bell operating company, Competitive local exchange carrier

See also: US telephony.