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The telephone or phone is a telecommunications device that transmits speech by means of electric signals.
The telephone was invented around 1860 by Antonio Meucci who called it teletrophone. The first recorded public demonstration of Meucci's invention took place in 1860, and had a description of it published in New York's Italian language newspaper.
In 1860 Johhan Philipp Reis produced a telephone which could transmit musical notes, and even a lisping word or two; and some ten years later Mr. Cromwell Fleetwood Varley, F.R.S., a well-known English electrician, patented a number of ingenious devices for applying the musical telephone to transmit messages by dividing the notes into short or long signals, after the Morse code, which could be interpreted by the ear or by the eye in causing them to mark a moving paper. These inventions were not put in practice; but four years afterwards Herr Paul la Cour, a Danish inventor, experimented with a similar appliance 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. By breaking up the note at the sending station with a signalling key, the message was heard as a series of long and short hums. 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.
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 also invented a 'physiological receiver,' which has a curious history. Early in 1874 his nephew was playing with a small induction coil, and, having connected one end of the secondary circuit to the zinc lining of a bath, which was dry, he was holding the other end in his left hand. While he rubbed the zinc with his right hand Gray noticed that a sound proceeded from it, which had the pitch and quality of the note emitted by the vibrating contact or electrotome of the coil. 'I immediately took the electrode in my hand,' he writes, 'and, repeating the operation, found to my astonishment that by rubbing hard and rapidly I could make a much louder sound than the electrotome. I then changed the pitch of the vibration, and found that the pitch of the sound under
my hand was also changed, agreeing with that of the vibration.' Gray lost no time in applying this chance discovery by designing the physiological receiver, which consists of a sounding-box having a zinc face and mounted on an axle, so that it can be revolved by a handle. One wire of the circuit is connected to the revolving zinc, and the other wire is connected to the finger which rubs on the zinc. The sounds are quite distinct, and would seem to be produced by a
microphonic action between the skin and the metal.
All these apparatus follow in the track of Reis and Bourseul--that is to say, the interruption of the current by a vibrating contact. It was fortunate for Bell that in working with his musical telephone an accident drove him into a new path, which ultimately brought him to the invention of a speaking telephone. He began his researches in 1874 with a musical telephone, in which he employed the interrupted current to vibrate the receiver, which consisted of an electro-magnet causing an iron reed or tongue to vibrate; but, while trying it one day with his assistant, Mr. Thomas A. Watson, 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 thereupon 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.
Reis had seen that an undulatory current was needed to transmit sounds in perfection, especially vocal sounds; but his mode of producing the undulations was defective from a mechanical and electrical point of view. By forming 'waves' of magnetic disturbance near a coil of wire, Professor Bell could generate corresponding waves of electricity in the line so delicate and continuous that all the modulations of sound could be reproduced at a distance.
As Professor of Vocal Physiology in the University of Boston, he 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.
On the suggestion of Dr. Clarence J. Blake, an eminent Boston aurist, Professor Bell abandoned the phonautograph for the human ear, which it resembled; and, having removed the stapes bone, moistened the drum with glycerine and water, attached a stylus of hay to the nicus or anvil, and obtained a beautiful series of curves in imitation of the vocal sounds. The disproportion between the slight mass of the drum and the bones it actuated, is said to have suggested to him the employment of goldbeater's skin as membrane in his speaking telephone. Be this as it may, he devised a receiver, consisting of a stretched diaphragm or drum of this material having 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.
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 telephone call 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. The first long distance telephone call was made on August 10, 1876 by Alexander Graham 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 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.
The primitive telephone has been greatly 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.
This later form 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.'
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.
The very early constructions of the telephone was based on sound transportation through air 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 inventions made by Meucci et al transported the sound through pipes.
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.
The network that connects most phones together is known as the PSTN (public switched telephone network).
Fixed phone lines are usually copper wirelines which form a circuit between the subscriber and a subscriber-line interface. The 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 pwoer-failure. Further, the dial-tone is presented only when the SLI's, 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 (CCITT recommends "0") followed by area code and a number local to that area. International phone calls require an international prefix (CCITT 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 PABX (Private Automatic Branch Exchange). 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 ISDN (Integrated Services Digital Network).
Between switches in the PSTN, most signalling is now digital using
Signalling System 7 ("SS7").
On the opening of the telephone exchange in Budapest, 1881, Nikola Tesla became the chief electrician to the telephone company (later engineer for the Yugoslav government and the country's first telephone system). Tesla invented a precursor to modern wireless telephone, known as a telephone repeater (or sometimes a amplifier). The device could act as a audio speaker (not a audio transducer). The device had it's resonance tuned to a particular frequency of other repeaters to communicate between each. In 1916, Tesla described the prior developed audio transducers. According to Tesla, it was the "... [S]implest ways [to detect the radiant energy ...] the low frequency gave audible notes. [... in a field, ther was] placed a conductor, a wire or a coil, and then [Tesla] would get a note [...] characteristics of the audible note". The audible sounds were of the quality of the telephones diaphragms of that period of time. The invention was never patented nor released publicly (till years later by Tesla himself). The device also contained the following characteristics:
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.
There are many standards for common carrier wireless telephony, often with incompatible standards used in the same nation:
610 (telephone),
431A,
ADSL,
AIOD leads,
Answering machine,
ANAC,
ANI,
Area code,
Assistive Technology,
Automatic redial,
Basic exchange telecommunications radio service,
Bell System,
Blue box,
Bomb threat,
Call center,
Call forwarding,
Call originator,
Call waiting,
Called party,
Caller,
Caller ID,
Calling party,
Camp-on busy signal,
COCOT,
Competitive local exchange company (CLEC),
Computer telephony integration (CTI),
Crank call,
Customer premises equipment (CPE),
Deaf,
Demon dialing,
Dial Tone,
Digital subscriber line,
Direct dial,
Direct distance dialing,
Dual tone multi frequency (DTMF),
Emergency telephone number,
End instrument,
Fax,
Foreign exchange service,
Help desk,
Hunt Group,
Incumbent local exchange company (ILEC),
Infrastructure,
Interactive voice response (IVR),
Line,
Local exchange company (LEC),
Local loop,
Long-distance operator,
Operator assistance,
Party line,
Modem,
Payphone,
Pen Register,
Person-to-person,
Plain Old Telephone Service (POTS),
Phone,
Phone phreaking,
Photophone,
Phreaking,
Post office,
Prank call,
Private line,
Public Switched Telephone Network (PSTN),
Red telephone box,
Red Box,
Regional Bell operating company (RBOC),
Ringer equivalency number (REN),
Ringing signal,
Rural radio service,
Smartphone,
Station-to-station,
Switchboard,
TAPI,
Telautograph,
Telecommunications Device for the Deaf (TDD or TTY),
Telemarketing,
Telephone booth,
Telephone call,
Telephone card,
Telephone directory,
Telephone exchange,
Telephone tapping,
Telegraph,
Telemarketing,
Teletype,
Telex,
Trap and trace,
TWX,
Vertical service code,
Videotex,
Voice over Internet Protocol (VOIP),
Voicemail,
War dialing,
Western Union,
Wide Area Telephone Service (WATS),
WATS line,
Wireless network,
Wi-Fi,
Zenith number
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
History
Land-line based phone systems and fixed telephony
Cordless telephones
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
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. 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 (in alphabetic order):
AT&T, BC TEL, Belgacom, Bell, BellSouth, Bell Canada, British Telecom, Cable and Wireless, Deutsche Telekom, Etisalat, IDT, ITT, MCI, NTL, NTT, OTE, Qwest, SBC Communications, Sprint, Telefonica, Teleglobe, Telewest, Telstra, Telia, TELUS, Verizon
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US-specific