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 Cell phones were invented in 1947 by the American company AT&T, but they became portable in a practical way in 1983 when Motorola finished the DynaTAC 8000X project, which was officially introduced in 1984.
The DynaTAC 8000X weighed approximately 2.2 pounds and it was 13x1,75x3,5 inches in dimension, it featured one hour of talking time and eight hours of stand by time and it had a LED display.
A cell phone is an electronic communication device with the same basic capacities of a conventional land phone. Besides being portable, it’s cordless since it doesn’t need a cable to be connected to the phone network.
The cell phone network is a phone system in which, through the combination of a network of radio transmitter-receptor stations (bases) and a series of commuting stations, it’s possible to establish a communication between portable phones (cell phones) or other portable terminals and land phones.
Functioning
The use of the word cell to refer to cordless phone services, is due to the fact that the bases, which are placed forming a net, forming cells (theoretically like a honeycomb). In that way, each base is located in a knot of these cells and a series of transmission and reception frequencies are assigned to it. Since the number of frequencies is limited, the arrangement of the bases allows to reuse the same frequencies in other cells, as long as they aren’t adjoining, to avoid any interference.
Basically, there are two types of cell phone networks:
Analogic Cell phone service network. This communication network works through analogic voice signals both in the radioelectric and land fields. In its first version it worked in the 450 MHz radioelectrical band and it later moved to the 900 MHz.
Digital Cell phone service network. This network works through digital signals, which allows to optimize both the use of the radiofrequence bands and the quality of the transmission. Its most important promoter is the standard GSM and its third generation, UMTS.
The advance of technology has allowed cell phones to include functions that seemed futuristic a few years ago, such as games, MP3 music players, email, SMS, digital cameras, Internet connection and even digital television. Cell phone operators are planning to add new functions to this small gadget that goes with us everywhere. |
