cellular telephone

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Related to cellular telephone: Cellular radio

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 ?
The Department of Justice's Community Policing Consortium will approve applications for cellular telephones after screening by local law enforcement agencies.
The nature of our agreement requires that we do not disclose its identity, but we can say that it is one of the foremost cellular telephone service providers in the nation," the CEO said.
Megahertz is a leading supplier of solution-oriented mobile data communications products and manufactures PCMCIA data/fax modems, PCMCIA cellular data/fax modems for selected cellular telephones, PCMCIA Ethernet-Modems, PCMCIA Ethernet adapters and external "pocket" modems.
Millions of people do not have access to voice telecommunication or communications devices making it difficult and oftentimes impossible to use a cellular telephone, use a telephone on the job or in a hotel room, to call 911 in an emergency, or use a headset to hear a computer," said Jo Waldron, who was honored by President Ronald Reagan with "The President's Trophy" and was appointed Disabled American for the Nation, representing the Presidents of the United States and all Americans with disabilities since 1987.
We are extremely pleased to be awarded this significant contract which promises to improve both the capacity and quality of the cellular telephone service available to the Taiwanese people," said Art MacDonald, chairman of Nortel China, Northern Telecom's business unit for Greater China.
Major equipment businesses include cellular telephone, two- way radio, paging and data communications, personal communications, automotive, defense and space electronics and computers.
AirCell designs, manufactures, markets and supports a full product line of airborne cellular telephone and data systems and services for the Business Aviation, General Aviation, and Air Transport markets.
OTCBB:GOSN) proudly reports that it has been designated as a Grade "A" Agent of the Guangzhou branch of China Mobile Communications Corporation, China's largest cellular telephone service provider.
There are many devices which claim to reduce the amount of radiation during cellular telephone use," said Frank Liu, CEO of Unical/Northwestern Bell Phones.
The first product the Company anticipates bringing to market is a cellular telephone battery, to be followed by a computer laptop battery.
April 18 /PRNewswire/ -- Today, Motorola's Cellular Subscriber Group announced plans to expand its cellular telephone operations by building a new manufacturing, engineering and administrative facility of approximately one million square feet in Harvard, Illinois.
The commercial potential of the VoiceSelect system is underscored by the explosive growth of cellular telephone use in the United States.

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