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[Mobile phone
Several mobile phones
A mobile or cellular telephone is a long-range, portable electronic device for personal telecommunications over long distances. In addition to the standard voice function of a telephone, current mobile phones can support many additional services such as SMS for text messaging, email, packet switching for access to the Internet, and MMS for sending and receiving photos and video. Most current mobile phones connect to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN) (the exception are satellite phones).
Mobile phones are distinct from cordless telephones, which generally operate only within a limited range of a specific base station. Technically, the term mobile phone includes such devices as satellite phones and pre-cellular mobile phones such as those operating via MTS which do not have a cellular network, whereas the related term cell(ular) phone does not. In practice, the two terms are used nearly interchangeably.
History
Mobile phones from various years, ranging from a large late 1980s-era phone to tiny 2000s phones
The Mobile phone is one of the most used pieces of equipment today. The concept of using hexagonal cells for mobile phone base stations was invented in 1947 by Bell Labs engineers at AT&T and was further developed by Bell Labs during the 1960s. Radiophones have a long and varied history that stretches back to the Second World War when the military started to use radio telephony links and civil services in the 1950s, with hand-held cellular radio devices being available since 1983. Due to their low establishment costs and rapid deployment, mobile phone networks have since spread rapidly throughout the world, outstripping the growth of fixed telephony
In 1945, the 0G generation of mobile telephones were introduced. 0G mobile telephones, such as Mobile Telephone Service, were not officially categorized as mobile phones, since they did not support the automatic change of channel frequency in the middle of a call, when the user moved from one cell (base station coverage area) to another cell, a feature called "handover".
Mock-up of the "portable phone of the future", from a mid-1960s Bell System advertisement, shows a device not too different from today's mobile telephones.
In 1970 Amos Joel of Bell Labs invented the "call handoff" feature, which allowed a mobile-phone user to travel through several cells during the same conversation. Martin Cooper of Motorola is widely considered to be the inventor of the first practical mobile phone for handheld use in a non-vehicle setting. Using a modern, if somewhat heavy portable handset, Cooper made the first call on a handheld mobile phone on April 3, 1973. At the time he made his call, Cooper was working as Motorola's General Manager of its Communications Division.
Fully automatic cellular networks were first introduced in the early to mid-1980s (the 1G generation). The first fully automatic mobile phone system was the 1981 Nordic Mobile Telephone (NMT) system. Until the late 1980s, most mobile phones were too large to be carried in a jacket pocket, so they were usually permanently installed in vehicles as car phones. With the advance of miniaturization and smaller digital components, mobile phones got smaller and lighter.
Manufacturers
Nokia Corporation is currently the world's largest manufacturer of mobile telephones, with a global market share of approximately 36% in Q4 of 2006. Other mobile phone manufacturers include Apple Inc., Audiovox (now UT Starcom), Benefon, BenQ-Siemens, High Tech Computer Corporation, Fujitsu, Kyocera, 3G, LG, Motorola, NEC, HTC, Panasonic (Matsushita Electric), Pantech Curitel, Philips, Research in Motion, Sagem, Samsung, Sanyo, Sharp, Siemens, Sierra Wireless, SK Teletech, Sony Ericsson, T&A Alcatel, and Toshiba. There are also specialist communication systems related to, but distinct from mobile phones, such as for exampleProfessional Mobile Radio.
Applications
Mobile news services are expanding with many organizations providing "on-demand" news services by SMS. Some also provide "instant" news pushed out by SMS. Mobile telephony also facilitates activism and public journalism being explored by Reuters and Yahoo and small independent news companies such as Jasmine News in Sri Lanka.
Health impacts
Since the introduction of mobile phones, concerns have been raised about the potential health impacts from cellular phone use.[13] Studies from the National Cancer Institute and researchers at the Danish Institute of Cancer Epidemiology in Copenhagen do not show any link between cellular phone use and cancer. The Danish study only covered analog mobile phone usage up through 1995, and subjects who started mobile phone usage after 1995 were counted as non-users in the study. However, a study by the International Agency for Research on Cancer of 4,500 users found a statistically significant link between tumor frequency and mobile phone use
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موضوع: التطور في مجال الاتصالات 
20/11/2009, 00:16
