1.2.2 Charles Bourseul

In 1854 in the magazine "L'Illustration de Paris" M. Charles Bourseul, a French telegraphist, published 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.'

1.2.3 Johann Philipp Reis

In 1860 Johann Philipp ReisJohann Philipp Reis ( January 7, 1834 January 24, 1874), was born in Gelnhausen, Germany, as son to a Jewish baker. He was self-taught scientist and inventor who constructed one of the first working telephones. See Reis' telephone). Early life and educati 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".

1.2.4 Cromwell Varley

Around 1870Events January 6 The inauguration of the Musikverein ( Vienna). January 10 John D. Rockefeller incorporates Standard Oil January 15 A political cartoon for the first time symbolizes the United States Democratic Party with a donkey ("A Live Jackass Kicking 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.

1.2.5 Poul la Cour

Around 1874Events January 1 New York City annexes The Bronx January 23 Marriage of the Duke of Edinburgh, second son of Queen Victoria, to Grand Duchess Maria Alexandrovna of Russia, only daughter of Emperor Alexander III of Russia. January Signing of the Pangkor Tr 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 electromagnetAn electromagnet is a type of magnet in which the magnetic field is induced by a flow of electric current. The magnetic field disappears when the current ceases. right-hand rule. The simplest type of electromagnet is a coil of wire. A coil forming the sha, 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.

1.2.6 Elisha Gray

Mr. Elisha GrayElisha Gray ( August 2, 1835 January 21, 1901) independently invented the telephone in his laboratory in Highland Park, Illinois. Born in Barnesville, Ohio, Gray was brought up on a farm. He spent two years at Oberlin College where he worked with electric, of Chicago also devised a tone telegraph of this kind about the same time as Herr La Cour. In this apparatus a vibrating steel reed interrupted the current, which at the other end of the line passed through an electromagnet and vibrated a matching steel reed near its poles. Gray's 'harmonic telegraph,' with the vibrating reeds, was used by the Western Union Telegraph Company. Since more than one set of vibrations--that is to say, more than one note--can be sent over the same wire simultaneously, the harmonic telegraph can be utilised as a 'multiplex' or many-ply telegraph, conveying several messages through the same wire at once; and these can either be read by the operator by the sound, or a permanent record can be made by 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.

1.3 Carbon Grain transmitter

1.3.1 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 1980s, and is still produced.

1.4 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.

1.4.1 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.

1.4.2 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.

1.4.3 Public demonstrations

1.4.3.1 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.

1.4.3.2 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 Star-Spangled Banner", and "Hail Columbia," while the audience at Salem joined in the chorus.'

1.4.4 Summary of Bell's achievements

Bell adopted Gray's, 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.

1.5 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.

1.6 Misc

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), and 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.

2 Land-fixed phone systems

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2.1 Fixed Cordless telephones

Cordless telephones consist of a base unit that connects to the land-line

system and also communicates with remote handset s 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.

3 Wireless phone systems

They are the satellite and mobile systems.

3.1 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 Yugoslavian 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:

• Antennas (aerial wire)
• Ground connections
• Antenna-ground circuits containing inductance and capacity ( RLC circuit)
• Adjustable inductors and capacitors (for tuning)
• Sending and receiving sets tuned to resonance with each other

3.2 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.

3.3 Standards

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

• First generation - Analog
  • marine and mobile radio telephony
  • AMPS
    • CDPD data service on AMPS
  • NMT
• Satellite systems- digital
  • Inmarsat
  • Iridium (satellite)
• Second generation ( 2G) - Digital
  • CDMA IS-95A
  • GSM, (different frequencies for different continents: see GSM article)
  • iDEN
  • TDMA IS-136
• 2.5G
  • CDMA IS-95B
  • GPRS
  • EDGE
  • PDC-P
• Third generation ( 3G)
  • CDMA 2000
  • UMTS, also called W-CDMA
  • TD-SCDMA

4 Telephone equipment manufacturers

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

• Alcatel
• Ericsson
• Huawei
• Lucent
• Marconi
• Motorola
• Nokia
• Nortel
• Samsung
• Siemens AG
• Sony Ericsson

5 Telephone equipment research labs

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

6 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 also: List of telephone operating companies

7 See also

7.1 Telephone equipment

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

7.2 Telephone technology

• 1-4-7-1
• Asymmetric Digital Subscriber Line (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 (DSL)
• 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)

7.3 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

7.4 Telephone hacking and exploitation

• Blue box
• Bomb threat
• Crank (or prank) call
• Demon dialing
• (Phone) phreaking
• Telephone fraud
• War dialing

7.5 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,
• Ringer equivalency number (REN)
• Ringing signal
• Rural radio service
• Smartphone
• Station-to-station
• Telemarketing
• Telephone booth
• Telephone call
• Telephone card
• Telephone directory
• Telephone exchange
• Telephone tapping
• Telephony Application Programming Interface (TAPI)
• Trap and trace
• TWX
• Vertical service code
• Voicemail
• Western Union
• Wide Area Telephone Service (WATS)
• WATS line
• Wireless network
• Wi-Fi
• Zenith number

7.6 US-specific

• Competitive local exchange carrier (CLEC)
• Federal Standard 1037C
• Interexchange carrier (IXC)
• List of telephony terms
• Local access and transport area (LATA)
• Local exchange carrier (LEC)
• Modification of Final Judgment
• Federal Regulations - Part 68
• Regional Bell operating company (RBOC)
• US telephony

8 References

• Huurdeman, Anton A. (2003). The Worldwide History of Telecommunications, IEEE Press and J. Wiley & Sons, 2003. BooksEnthsiast.com

9 External link

• http://www.dlci.net/glossary.htm

Telephony Office equipment

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