Cellphone(CELLULAR TELEPHONE) The first ubiquitous wireless telephone. Originally analog, all new cellular systems are digital, which has enabled the cellphone to turn into a smartphone that has access to the Internet. Digital cellphone systems are also offered in the PCS band, which is radio spectrum that was auctioned off by the U.S. government in the mid-1990s. Introduced in the mid-1980s, cellphone sales exploded worldwide in the 1990s. Outside the U.S., cellphones are also called "mobile phones" or "mobiles."
Major Carriers
In the U.S., the major cellular carriers by total subscribers at the end of 2005, starting with the largest, are Cingular Wireless (formerly Cellular One and including AT&T Wireless), Verizon Wireless (formerly Bell Atlantic Mobile), Sprint Nextel (merger of Sprint and Nextel) and T-Mobile. The largest cellular company in the world is UK-based Vodafone with 2005 revenues exceeding $60 billion. As of 2006, Vodaphone had a substantial ownership in Verizon Wireless.
Cell Technology
Geographic areas are divided into a number of slightly overlapping circular "cells." Each cell contains a base station, which is identifiable by its transmitting and receiving antenna located on a tower at the top of a hill or building. The base stations connect to the landline telephone system of the country.
The multiple cells combined with low power transmitters allow the same frequencies to be reused with different conversations in different cells within the same city or locale. The primary digital cellphone technologies are TDMA, CDMA and GSM. See 3G, AMPS, GSM, TDMA, CDMA, WAP, cellspace, smartphone, screaming cellphone and cordless phone.
Source:- www.answers.com
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