The telephone or phone (Greek: tele = far away and phone = voice) 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

There are four principal means by which an end user using a telephone handset may connect to a telephone network: a traditional fixed phone "landline", which uses dedicated physical wire connections connected to a single location; wireless and radio telephones, which use either analog or digital radio signals; satellite telephones, which utilize telecommunications satellites; and voice over internet protocol (VOIP) telephones, which use broadband internet connections.

Between end users, transmissions across a network may be carried by fiber optic cable, point to point microwave or satellite relay.

Until relatively recently, a "telephone" generally referred only to landlines. Cordless and mobile phones are now common in many places around the world, with mobile phones expected to gradually displace the conventional landline telephone. Unlike a mobile phone, a cordless telephone is considered to be landline because it is only useable within a short distance of a small personal or domestic base station connected to a fixed phone line.

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

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 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.

Early development

The following is a brief summary 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.
• 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

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, 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 fiber 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 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, 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.

VoIP Telephony

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 switched from analog to digital telephone service. A recent Newsweek article suggested that Internet telephony may be "the next big thing."

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 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) are in competition to provide telephone 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

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.