cellular telephone

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cellular telephone


cellular radio,

telecommunications system in which a portable or mobile radio transmitter and receiver, or "cellphone," is linked via microwavemicrowave,
electromagnetic wave having a frequency range from 1,000 megahertz (MHz) to 300,000 MHz, corresponding to a wavelength range from 300 mm (about 12 in.) to 1 mm (about 0.04 in.). Like light waves, microwaves travel essentially in straight lines.
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 radio frequencies to base transmitter and receiver stations that connect the user to a conventional telephone network. The geographic region served by a cellular system is subdivided into areas called cells. Each cell has a central base station and two sets of assigned transmission frequencies; one set is used by the base station, and the other by cellphones. To prevent radio interference, each cell uses frequencies different from those used by its surrounding cells, but cells sufficiently distant from each other can use the same frequencies. When a cellphone leaves one cell and enters another, the telephone call is transferred from one base station and set of transmission frequencies to the next using a computerized switching system.

A camera phone is a cellular phone that also has picture taking and often video recording capabilities; the pictures and videos may be sent to another cellular phone or to a computer. Most cellphones are now so equipped, and also have the ability to send text messages. Further advances in digital technology and microelectronics have led to the development of so-called smartphones, which typically also include e-mail programs, Internet browsers, personal information managers, music and video players, alarm clocks, calculators, games, voice memo recorders, e-book readers, and many other specialized software applications, or apps. Such phones typically have touch screens for accessing data and content, and are usually capable of accessing the Internet through a wireless network connection as well as through the cellular telephone system. These features have allowed smartphones to replace personal digital assistants, portable music players, and other portable electronic devices, and also supplant portable computers in many uses. The increasing size of smartphone screens has blurred most of the distinctions between the largest smartphones and smallest computer tablets, though the largest smartphones can be awkward when used for making telephone calls. The software needed for smartphone programs can make the devices vulnerable to software viruses.

The first cellular telephone system began operation in Tokyo in 1979, and the first U.S. system began operation in 1983 in Chicago. In many countries with inadequate wire-based telephone networks, cellular telephone systems have provided a means of more quickly establishing a national telecommunications network.

Cellphones emit nonionizing radiation, and there have been concerns expressed about whether they might cause cancer. Studies on the subject that have found evidence of increased cancer rates have been criticized for having methodological flaws. Although a World Health Organization panel concluded in 2011 that cellular phones were "possibly carcinogenic," that finding was criticized by the American Cancer Society and the National Cancer Institute and undermined by a large Danish study published in 2011.

References in periodicals archive ?
2001; Violanti & Marshall, 1996) to determine the frequency of cellular phone use while driving, no study has addressed the issue of whether perceptions differ between cellular phone users and nonusers on issues pertaining to vehicular safety and laws.
to provide free cellular phones to registered participants of our adult day healthcare program, residents in independent living apartments and those being discharged from the nursing facility to home.
The authors of the study emphasized that their results apply only to cellular phones -- not to cordless household phones, which do not send out such signals.
group funded primarily by the cellular phone industry.
Indeed, the cost to run a successful venture of this magnitude, which would include cellular phone equipment and air time, could prove prohibitive.
Synthetic pesticides assure us a plentiful and cheap supply of fresh fruits and vegetables; power lines give us light and warmth that formerly were provided by such terribly dangerous and polluting substances as kerosene and coal, and they give us coolness that was simply unavailable; cellular phones are regularly used to transmit emergency information concerning traffic accidents and crimes; automobiles have rid us of streets paved with pony poo and the terrible diseases that accompanied it; food irradiation could have prevented the recent outbreak of bacteria from fast-food hamburgers that has killed three children and made hundreds of persons ill, but the irradiation technophobes have managed to keep it practically nonexistent in the United States.
The price of cellular phones has been reduced from $3,000 to under $300 for some models, but cellular service costs are still fairly high.
Combined, they currently have about 4,000 cellular phone customers in Northern Ontario.

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