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Telephone

Complex relay used in a telephone switching system.

This article is about telephone technology. For the game of telephone, see Telephone (game). For the band, see Téléphone.

The telephone or phone (Greek: tele = far away and phone = voice) is a telecommunications device that transmits and receives sound (most commonly voice and speech) through great distances. Most telephones operate by means of electric signals over a complex public switched telephone network of equipment which allows almost any phone user to speak to almost any other.

Until relatively recently the word telephone could generally be assumed to refer to a landline phone. Now, cordless telephones and cell phones have become sufficiently common that no such presumption can be made. There are four principal means by which telephone signals are transmitted: through a traditional landline which uses physical dedicated wire connections; wireless or Radiotelephony, which transmits messages using either analog or digital radio signals; satellite telephones which bounce signals off of telecommunications satelites; and voice over internet protocol (VOIP) telephones, which use broadband internet cables.

The electric telephone is attributed to various inventors. The actual history is a subject of complex dispute. Among others Antonio Meucci, Philip Reis, and Alexander Graham Bell are all cred with inventing.

History

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. 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 instead of scientific publication and demonstrating to fellow scientists.

It is important to note that there is probably no one "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.

Early development

The following is a brief summery of the history of the invention of the telephone:

• 1849 Antonio Meucci demonstrates a device later called a telephone to individuals in Havana. (The demonstration involves direct electrical connections to people. See Physiophony)
• 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. 1
• 1860 Johann Philipp Reis demonstrates a make-break transmitter after the design of Bourseul.
• 1860 Meucci supposedly demonstrates his telephone on Staten Island.
• 1861 Reis manages to transfer voice electrically over a distance of 340 feet, see Reis' telephone.
• 1871 Meucci files a patent caveat (a statement of intention to patent).
• 1872 Elisha Gray founds Western Electric Manufacturing Company.
• July 1873 Thomas Alva Edison notes variable resistance in carbon grains due to pressure, but shelves the discovery.
• 1874 Gray demonstrates his liquid transmitter telephone at the Highland Park Presbyterian Church.
• 2 June 1875 Alexander Graham Bell first transmits voice.
• 1 July 1875 Bell first uses a bi-directional capable telephone (Both the transmitter and the receiver were identical membrane instruments.)
• 14 February 1876 Bell files his first patent on the telephone.
  • Two hours later Gray files his patent caveat.
• 30 January 1877 Bell patents the electro-dynamic transmitter, receiver telephone telephone

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

Later history

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.

In 1926 Bell Laboratories 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

Digital telephony emerged when end-to-end analog circuits were replaced by islands of digital circuits. Advances in digital transmission technology made it possible to carry multiple digital circuits on a single transmission medium Multiplexing. While the end instrument remained analog, the analog signals reaching the aggregation point Serving Area Interface SAI or the Central Office CO were converted to digital signals. Digital Loop Carriers DLC carried multiple analog telephone lines to the CO after converting them to digital signals, initially in fewer copper pairs and later on optical fiber. COs were interconnected by SONET carriers.

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) used in the television show Star Trek.

Fixed Cordless telephones

Cordless handset

Cordless telephones, first 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 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

Wireless phones systems include Cell phones are the satellite and mobile systems. For non-telephone-network uses see Radio.

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 (PSTN) 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.

VoIP Telephony

A WiFiased VoIP phone

Also known as Internet telephony or Voice over IP (VoIP), digital telephony is a disruptive technology that is rapidly replacing traditional telephone networks. In Japan and Korea up to 10% of subscribers, as of January 2005, have switch from analog to digital telephone service. A recent Newsweek article suggested that Internet telephony may be "the next big thing." 2

Digital telephones use a broadband Internet connection to transmit conversations as data packets. In addition to replacing the PSTN, digital telephony is also competing with mobile phone networks by offering free connections via WiFi hotspots.

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 also: List of telephone operating companies

See also

References

• Huurdeman, Anton A. (2003). The Worldwide History of Telecommunications, IEEE Press and J. Wiley & Sons, 2003. ISBN 0471205052

Patents

• US174465 -- Telegraph -- A. G. Bell

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