   #copyright

Telephone

2007 Schools Wikipedia Selection. Related subjects: Engineering

   A French rotary telephone
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   A French rotary telephone
   A basic modern telephone
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   A basic modern telephone
   Touch-tone telephone
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   Touch-tone telephone
   A touch-tone telephone keypad
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   A touch-tone telephone keypad
   Copy of the original phone of Graham Bell at the Musée des Arts et
   Métiers in Paris
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   Copy of the original phone of Graham Bell at the Musée des Arts et
   Métiers in Paris
   1896 Telephone (Sweden)
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   1896 Telephone (Sweden)
   A telephone handset
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   A telephone handset

   The telephone or phone is a telecommunications device which is used to
   transmit and receive sound (most commonly voice and speech) across
   distance. Most telephones operate through transmission of electric
   signals over a complex telephone network which allows almost any phone
   user to communicate with almost any other.

Introduction

   An elementary telephone system consists of three elements:
     * For each subscriber, the system must contain the equipment
       necessary to convert sound to electrical signals and back. This
       allows the subscriber to answer or initiate a call.
     * The system must contain a central switching facility which
       interconnects all the subscribers.
     * Finally, the system requires wiring or other means to connect the
       subscribers to the central switching facility.

   There are three principal ways a subscriber may be connected to the
   telephone network:
     * Historically, and still very commonly, by dedicated physical wire
       connections run in overhead or underground cables;
     * By radio, as in a cordless, cellular, satellite or radiotelephone
       and
     * By voice over internet protocol (VoIP) telephones, which use
       broadband internet connections.

History

   The identity of the inventor of the electric telephone remains in
   dispute. Antonio Meucci, Johann Philipp Reis, Alexander Graham Bell and
   Elisha Gray, amongst others, have all been credited with the invention.

   The very 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. Much money was
   expended, 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 demonstration to investors instead of scientific
   publication and demonstration to fellow scientists. It is important to
   note that there is probably no single "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. Only in the last ten
   years, however, has the British government announced that it now
   recognizes (primarily for educational purposes) Antonio Meucci (see
   below) as the 'first inventor' of the telephone. This was acknowledged
   even by the US Congress in 2003 .

Early development

   The following is a brief summary of the history of the invention of the
   telephone:
     * 1849 Antonio Meucci demonstrates a device he later called a
       telephone to individuals in Havana. (The demonstration involves
       direct electrical connections to people.)
     * 1854 Charles Bourseul publishes a description of a make-break
       telephone transmitter and receiver but does not construct a working
       instrument.
     * 1854 Meucci demonstrates an electric telephone in New York.
     * 1860 Johann Philipp Reis demonstrates a "telephon" using a pressure
       contact transmitter after the make-break design of Bourseul and a
       knitting needle receiver. Witnesses said they heard human voices
       being transmitted.
     * 1860 Meucci demonstrates his telephone on Staten Island.
     * 1861 Reis manages to transfer voice electrically over a distance of
       340 feet, see Reis' telephone.
     * 1864 In an attempt to give his musical automaton a voice, Innocenzo
       Manzetti invents the 'Speaking telegraph'. He shows no interest in
       patenting his device, but it is reported in newspapers.
     * 1865 Meucci reads of Manzetti's invention and writes to the editors
       of two newspapers claiming priority and quoting his first
       experiment in 1849. He writes "I do not wish to deny Mr. Manzetti
       his invention, I only wish to observe that two thoughts could be
       found to contain the same discovery, and that by uniting the two
       ideas one can more easily reach the certainty about a thing this
       important." If he reads Meucci's offer of collaboration, Manzetti
       does not respond.
     * 1871 Meucci files a patent caveat (a statement of intention to
       patent).
     * 1872 Elisha Gray founds Western Electric Manufacturing Company.
     * 1872 Prof Vanderwyde demonstrated Reis's telephone in New York.
     * July 1873 Thomas Edison notes variable resistance in carbon grains
       due to pressure and builds a rheostat based on the principle.
     * May 1874 Gray invents electromagnet device for transmitting musical
       tones. Some of his receivers use steel diaphragms.
     * December 29, 1874 Gray demonstrates his musical tones device and
       transmitted "familiar melodies through telegraph wire" at the
       Presbyterian Church in Highland Park, Illinois.
     * 2 June 1875 Alexander Graham Bell transmits the sound of plucked
       steel reeds using electromagnet instruments.
     * 1 July 1875 Bell uses a bi-directional "gallows" telephone that was
       able to transmit "indistinct but voicelike sounds" but not clear
       speech. Both the transmitter and the receiver were identical
       membrane electromagnet instruments.
     * 1875 Thomas Edison experiments with acoustic telegraphy and in
       November builds an electro-dynamic receiver but does not exploit
       it.
     * 11 February 1876 Elisha Gray invents a liquid transmitter for use
       with a telephone, but does not build one.
     * 14 February 1876 (about 9:30 am) Gray or his lawyer brings to the
       Patent Office Gray's caveat for the telephone. (A caveat was a
       notice of intention to file a patent application)
     * 14 February 1876 (about 11:30am) Bell's lawyer brings to the Patent
       Office Bell's patent application for the telephone. Bell's lawyer
       requested that it be registered immediately in the cash blotter.
          + About two hours later Elisha Gray's caveat was registered in
            the cash blotter. Although Gray could have converted his
            caveat into a patent application, he did not do so.
     * 7 March 1876 Bell's US patent 174,465 for the telephone is granted.
     * 10 March 1876 Bell transmits speech "Mr. Watson, come here, I want
       you." using a liquid transmitter and an electromagnetic receiver.
     * 16 May 1876 Thomas Edison files first patent application for
       acoustic telegraphy.
     * 20 January 1877 Edison "first succeeded in transmitting over wires
       many articulated sentences" using carbon granules as a pressure
       sensitive variable resistance under the pressure of a diaphragm
       (Josephson, p143).
     * 30 January 1877 Bell's US patent 186,787 is granted for an
       electro-magnetic telephone using permanent magnets, iron
       diaphragms, and a call bell.
     * 4 March 1877 Emile Berliner invents a microphone based on the
       "loose contact" between two metal electrodes, an improvement on the
       Reis telephone, and in April 1877 files a caveat of an invention in
       process.
     * 27 April 1877 Edison files for a patent on a carbon (graphite)
       transmitter. The patent 474,230 was granted May 3, 1892 after a 15
       year delay due to litigation. In 1892 a federal court ruled Edison
       and not Berliner was the inventor of the carbon transmitter. Edison
       was granted patent 222,390 for a carbon granules transmitter in
       1879. Edison's carbon granules transmitter and Bell's
       electromagnetic receiver were used, with improvements, by the Bell
       system for many decades thereafter (Josephson, p 146).

Later history

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

   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, .AIF files and
   compact discs).

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

   The industry has 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.

   In 1926 Bell Labs and the British Post Office engineered the first
   two-way conversation across the Atlantic.

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

Digital Telephony

   The Public Switched Telephone Network (PSTN) has gradually evolved
   towards digital telephony which has improved the capacity and quality
   of the network. End-to-end analog telephone networks were first
   modified in the 1970s by upgrading long-haul transmission networks with
   SONET technology and fibre optic transmission methods. Digital
   transmission made it possible to carry multiple digitized switched
   circuits on a single transmission medium (known as multiplexing). While
   today the end instrument remains analog, the analog signals reaching
   the aggregation point ( Serving Area Interface (SAI) or the central
   office (CO) ) are typically converted to digital signals. Digital loop
   carriers (DLC) are often used, placing the digital network ever closer
   to the customer premises, relegating the analog local loop to legacy
   status.

Wireless phone systems

   While the term " wireless" means radio and can refer to any telephone
   that uses radio waves (such telephones have existed since 1915: see "
   Hello, Hawaii, How Are You?"), it is primarily used for cell phones. In
   the United States wireless companies tend to use the term wireless to
   refer to a wide range of services while the cell phone itself is called
   a mobile phone, mobile, PCS phone, cell phone or simply cell with the
   trend now moving towards mobile.

   The changes in terminology is partially due to providers using
   different terms in marketing to differentiate newer digital services
   from older analog systems and services of one company from another.

Cordless telephone

   Cordless handset
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   Cordless handset

   Cordless telephones, invented by Teri Pall in 1965, 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 electronic power supply. Thus, cordless phones typically do not
   function during power outages. Initially, cordless phones used the 1.7
   MHz frequency range to communicate between base and handset. Because of
   quality and range problems, these units were soon superseded by systems
   that used frequency modulation (FM) at higher frequency ranges (49 MHz,
   900 MHz, 2.4 GHz, and 5.8 GHz). The 2.4 GHz cordless phones can
   interfere with certain wireless LAN protocols ( 802.11b/g) due to the
   usage of the same frequencies. On the 2.4 GHz band, several "channels"
   are utilized in an attempt to guard against degradation in the quality
   of the voice signal due to crowding. The range of modern cordless
   phones is normally on the order of a few hundred meters.

Mobile phones

   Most modern mobile phone systems are cell-structured. Radio is used to
   communicate between a handset and nearby cell sites.

   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.

   Radio frequencies are a limited, shared resource. The higher
   frequencies used by cell phones have advantages over short distances.
   Connection distance is somewhat predictable and can be controlled by
   adjusting the power level. By only using enough power to connect to the
   "nearest" cell site phones using one cell site will cause almost no
   interference with phones using the same frequencies on another cell
   site. The higher frequencies also work well with various forms of
   multiplexing which allows more than one phone to connect to the same
   tower with the same set of frequencies.

Satellite phones

   Some mobile telephones, especially those used in remote locations,
   where constructing a cell network would be too unprofitable or
   difficult, instead communicate directly with an orbiting satellite.
   Such devices tend to be bulkier than cell-based mobile phones, as they
   require a large antenna or dish for communicating with the satellite,
   but do not require ground based transmitters, making them useful for
   communicating from remote areas and disaster zones.

Semi-Cordless Phone

   There are phones that work as a cordless phone when near their
   corresponding base station (and sometimes other base stations) and work
   as a wireless phone when in other locations but for a variety of
   reasons did not become popular.

   Some kinds of cordless phones work like cellular phones but only within
   a small private network covering a building or group of buildings.
   These kinds of systems using VoIP are popular in hospitals and
   factories where the same wireless network can be used for both data and
   voice.

IP Telephony

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

   Also known as Internet telephony, IP Telephony is a service based on
   Voice over IP (VoIP), a disruptive technology that is rapidly gaining
   ground against traditional telephone network technologies. In Japan and
   South Korea up to 10% of subscribers, as of January 2005, have switched
   to this digital telephone service. A recent Newsweek article suggested
   that Internet telephony may be "the next big thing."

   There are many IP Telephony providers in the market (such as Packet8,
   Vonage, and Sunrocket) at the moment, and statistics suggest over 40%
   of the world population will have switched to VoIP by year 2010.

   IP telephony uses a broadband Internet connection to transmit
   conversations as data packets. In addition to replacing POTS, IP
   telephony is also competing with mobile phone networks by offering free
   or lower cost connections via WiFi hotspots. As mentioned above VoIP is
   also used on private wireless networks which may or may not have a
   connection to the outside telephone network.

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 in American English) are in competition to provide
   telephone services. Some of them are included in the following list.
   However, the list only includes facilities based providers and not
   companies which lease services from facilities based providers in order
   to serve their customers. See also: List of telephone operating
   companies

Trivia

     * 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 (which in use actually more closely
       resembled walkie-talkies, Nextel-style) used in the television show
       Star Trek, though similar devices were seen in other TV shows
       before that.
     * In Unicode, telephones are depicted with the characters whose
       hexadecimal codes are 2121 (℡), 260E (☎), 260F (☏) and 2706 (✆),
       (but may not display properly in some browsers).

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 1940's.
     * 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) --
       Martin Cooper et al. (Motorola)

   Retrieved from " http://en.wikipedia.org/wiki/Telephone"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
