Tips & Definitions:
Data Technically, raw facts and figures, such as orders and payments, which are processed into information, such as balance due and quantity on hand. However, in common usage, the terms data and information are used synonymously. In addition, the term data is really the plural of "datum," which is one item of data. But datum is rarely used, and data is used as both singular and plural in practice. The amount of data versus information kept in the computer is a tradeoff. Data can be processed into different forms of information, but it takes time to sort and sum transactions. Up-to-date information can provide instant answers. A common misconception is that software is also data. Software is executed, or run, by the computer. Data are "processed." Thus, software causes the computer to process data. Any form of information whether on paper or in electronic form. Data may refer to any electronic file no matter what the format: database data, text, images, audio and video. Everything read and written by the computer can be considered data except for instructions in a program that are executed (software). May refer only to data stored in a database in contrast with text in a word processing document.
More recent telecommunications systems take advantage of some of these imperfections to actually improve the quality of the channel. Modern telecommunication systems often make extensive use of a clock signal which is used to decode a transmitted data stream, synchronization. In order to accumulate and manage such streams a telco always provided the clock signal. With the advent of global communications it became necessary to have a single worldwide standard derived from a master atomic clock, or to secondary clocks synchronised to that clock. Synchronous circuits are often used between routers. Asynchronous Transfer Mode, ATM is a relatively new standard, operating at very high bit rates where synchronization outside of the data stream can result in errors.
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 smart phone 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.
Major Carriers
In the U.S., the major cellular carriers by total subscribers at the end of 2004, 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 Vodaphone with 2003 revenues exceeding $60 billion. As of 2004, Vodaphone had a substantial ownership in Verizon Wireless.
Cell Technology
The concept behind a cellular system is that an area is divided into a number of slightly overlapping circular "cells." Each cell contains a base station, which is identifiable from its transmitting and receiving tower. 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 AMPS, GSM, TDMA, CDMA, WAP, cellspace, smart phone and cordless phone.
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