Telefon
From Wikipedia
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Telefon berasal daripada (bahasa Greek: tele = jauh dan phone = suara) adalah alat telekomunikasi yang digunakan bagi memancar dan menerima bunyi (kebiasaanya suara dan percakapan) pada jarak jauh tanpa terikat, secara bebas. Kebanyakan telefon beroperasi melalui pemancaran isyarat eletrik melalui jaringan telefon rumit yang membenarkan sebarang pengguna telefon untuk berhubung dengan hampir kesemua yang lain..
[Sunting] Pengenalan
Terdapat empat prinsip utama di mana pengguna yang menggunakan penerima telefon boleh disambungkan kepada jaringan telefon: "talian darat" tradisi telefon kekal, di mana sambungan wayar fizikal khusus digunakan bagi menyambungkan sesuatu lokasi; wireless dan telefon radio, yang menggunakan samaada isyarat radio analog atau digital; telefon satelit, yang menggunakan satelit komunikasi; dan telefon suara melalui protokol internet (VOIP), yang menggunakan perhubungan capaian Internet Jalur Lebar.
Antara pengguna akhir, pemancar antara jaringan boleh dilakukan melalui kabel gentian optik, titik ke titik microwave atau relay satelit.
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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.
==Sejarah==
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.
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.
[Sunting] 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
[Sunting] 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 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.
[Sunting] Telefoni Digital
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 (known as 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 on copper wire pairs and later on optical fiber. COs were interconnected by SONET carriers.
[Sunting] 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 used 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.
[Sunting] Cordless telephone
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 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.
[Sunting] Telefon selular
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 contolled 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.
[Sunting] Cordless/mobile 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 poplular in hospitals and factories where the same wireless network can be used for both data and voice.
[Sunting] 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 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 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.
[Sunting] Telephone equipment research labs
Bell Labs is a noted telephone equipment research laboratory, amongst its other research fields.
[Sunting] 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
[Sunting] 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.
[Sunting] Lihat juga
[Sunting] Telephone equipment
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[Sunting] Telephone equipment manufacturersSeveral manufacturers build telephones of all kinds. Some of these are: |
[Sunting] Telephone technology
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[Sunting] Telephone system, organization, and structure
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[Sunting] Telephone hacking and exploitation
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[Sunting] US-specific terminology
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[Sunting] Telephone terminology
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[Sunting] Telephone Standards[Sunting] Wired Standards
[Sunting] Wireless StandardsThere are many standards for common carrier wireless telephony, often with incompatible standards used in the same nation:
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[Sunting] References
- Huurdeman, Anton A. (2003). The Worldwide History of Telecommunications, IEEE Press and J. Wiley & Sons, 2003. ISBN 0471205052
[Sunting] Patents
- US174465 -- Telegraph -- A. G. Bellem:Telephone