Cell phone (telefone celular) is a wireless, portable, long-range, electronic telephone, which for the duration of travel may seamlessly modify antenna connections, from one radio reception cell to another radio reception cell, without dropping or losing the ongoing call.
Besides the general voice function of a telephone, latest cell phones (telefone celular) have features such as SMS for text messages, MMS for multimedia messages, radio, games, internet connectivity for email, browsing, blogging, music (MP3) playback, memo recording, built-in cameras and camcorders, ringtones, personal organizers, Push-to-Talk (PTT), Bluetooth and infrared connectivity, call registers, streaming video, downloading video, video call, and likewise serve as wireless modems for PCs that may be connected to the Internet.
The power in a cell phone (telefone celular) is received from rechargeable batteries, which may be recharged from the mains, a USB port or a cigarette lighter port in an automobile. Nickel Metal Hydride were the most mutual types of batteries, which due to the “memory effect” (the user may recharge only when the entire battery is drained off) were substituted by Lithium-Ion batteries, which did not suffer from any memory effect.
Cell phones (telefone celular) came into existence because of the invention of hexagonal cells in 1947, for the base stations by Bell Labs engineers at AT&T. This was further produced for the duration of the 1960s by Bell Labs. During a call, the channel frequency could not be changed mechanically from one cell (base station coverage area) to another cell (base station coverage area) as the person traveled from the area of one cell to the area of another cell. Amos Joel of Bell Labs developed a breakthrough invention and called it as the `call handoff` by which the channel frequency could be changed mechanically from one cell to another cell, for the duration of the same call, as the mobile user traveled from one cell to another cell. Due to their heavy construction, these phones were applied mainly in automobiles.
The initial practical cell phone in a non-vehicle setting, and which could be handheld, was developed by Martin Cooper, the General Manager (Communications Division) of Motorola, who made the world`s basi handheld cell phone (telefone celular) call on April 3, 1973.
The engineering by which the cell phone (telefone celular) works depends on the mobile phone operator; however, all of them use electromagnetic radio waves, which are in touch with a cell web site (base station). The base station is composed of various antennas which are mounted on a pole, tower, or building. Cell internet sites are disseminate at a distance of 5 to 8 miles (approx. 8 to 13 km) from each other. The low power transceiver from the cell phone transmits the voice and data to the nearest cell site. During movement, the cell phone will “handoff” the info to other cell site. Mobile phone operators use a heap of technologies to maintain the smooth stream of digitized selective information from the cell phone to the cell internetlocation and vice versa.
The wireless telephone technologies are grouped beneath heads known as generations, starting from zero generation or 0G. The current generation going on is 4G; however, there are old cell phones (telefone celular) that still operate on 1G, 2G, and 3G technologies. The wireless telephone technologies used in each generation are as given below:
0G: PTT, MTS, IMTS, AMTS, OLT, MTD, Autotel/PALM, ARP
1G: NMT, AMPS/TACS/ETACS, Hicap, CDPD, Mobitex, DataTac
2G: GSM, iDEN, D-AMPS, IS-95/cdmaOne, PDC, CSD, PHS, GPRS, HSCSD, WiDEN, CDMA2000 1xRTT/IS-2000, EDGE (EGPRS)
3G: W-CDMA, UMTS (3GSM), FOMA, TD-CDMA/UMTS-TDD, 1xEV-DO/IS-856, TD-SCDMA, GAN (UMA), HSPA, HSDPA, HSUPA, HSPA+, HSOPA
4G : UMB, UMTS Revision 8 (LTE), WiMAX
Frequency bands: SMR, Cellular, PCS
The affect of cell phone (telefone celular) usage on humane health has been of significant international concern. Research studies in Copenhagen, from the Danish Institute of Cancer Epidemiology, the National Cancer Institute, and the Institute of Cancer Research, do not establish any link among cancer and cell phone usage. However, an intergovernmental agency IARC (International Agency for Research on Cancer) forming percentage of the World Health Organization of the United Nations, undertook a study of 4,500 users and found a statistically substantial link amongst cell phone usage and tumor frequency. Further exploration is going on.
Cell phone (telefone celular) usage and driving is a mutual global phenomenon. Some jurisdictions have banned usage of hand-held phones for the duration of driving, but permitted the hands-free fashion of cell phone usage while driving. However, studies have found out that the distraction is caused by the speech itself; hence, both hand-held and hands-free cell phones bestow towards road traffic accidents. Further studies on cell phone usage and driving are going on.
Nokia Corporation is presently the world`s biggest manufacturer of cell phones (telefone celular). Other noteworthy cell phone manufacturers, in alphabetical order, are 3G, Audiovox (now UT Starcom), Benefon, BenQ-Siemens, Fujitsu, High Tech Computer Corporation (HTC), Kyocera, LG Mobile, Motorola, NEC, Panasonic (Matsushita Electric), Pantech Curitel, Philips, Research In Motion, Sagem, Samsung, Sanyo, Sharp, Siemens, Sierra Wireless, SK Teletech, Sony Ericsson, T&A Alcatel, Toshiba, and Verizon.
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