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Mobile phones What Are Mobile Phones

游客2023-07-18  27
问题                                         Mobile phones
    What Are Mobile Phones?
    A mobile phone, also known as a cellphone or cellular phone, is a portable electronic device which behaves as a normal telephone whilst being able to move over a wide area(compare cordless phone which acts as a telephone only within a limited range). Cellphones allow connections to be made to the telephone network, normally by directly dialing the other party’s number on an inbuilt keypad.  Most current cellphones use a combination of radio wave transmission and conventional telephone circuit switching, though packet switching is already in use for some parts of the cellphone network, especially for services such as Internet access and WAP.
    Some of the world’s largest cellphone manufacturers include Alcatel, Audiovox, Kyocera(formerly the handset division of Qualcomm), LG, Motorola, Nokia, Panasonic(Matsushita Electric), Philips, Sagem, Samsung, Sanyo, Siemens, SK Teletech, and Sony Ericsson.
    There are also specialist communication systems related to, but distinct from cellphones, such as satellite phones and Professional Mobile Radio.
    Worldwide Deployment
    Cellphones have a long and varied history that stretches back to the 1950s, with hand-held devices being available since 1983. Due to their low establishment costs and rapid deployment, cellphone networks have since spread rapidly throughout the world, outstripping the growth of fixed telephony.
    In most of Europe, wealthier parts of Asia, Australia, and the US, cellphones are now widely used, with the majority of the adult, teenage, and even child population owning one. The number of cell phone subscribers in the US has reached over 190 million. The availability of Prepaid or pay as you go services, where the subscriber does not have to commit to a long term contract, has helped fuel this growth.
    Standardized Technology
    The cellphone has become ubiquitous because of the interoperability of cellphones across different networks and countries. This is due to the equipment manufacturers all working to the same standard, particularly the GSM standard which was designed for Europe-wide interoperability. All European nations and some Asian nations chose it as their sole standard, while in Japan and South Korea another standard, CDMA, was selected.
    Cellphone Culture
    In less than twenty years, mobile phones have gone from being rare and expensive pieces of equipment used by businesses to a pervasive low-cost personal item. In many countries, cellphones now outnumber land-line telephones, with most adults and many children now owning cellphones. It is not uncommon for young adults to simply own a cell phone instead of a land-line for their residence. In some developing countries, where there is little existing fixed-line infrastructure, the mobile phone has become widespread.
    Social Life
    With high levels of mobile telephone penetration, a mobile culture has evolved, where the phone becomes a key social tool, and people rely on their cellphone addressbook to keep in touch with their friends. Many people keep in touch using SMS, and a whole culture of "texting" has developed from this. The commercial market in SMS’s is growing. Many phones even offer Instant Messenger services to increase the simplicity and ease of texting on phones.
    Entertainment
    The mobile phone itself has also become a totemic and fashion object, with users decorating, customizing, and accessorizing their cellphones to reflect their personality. Likewise, customized ringtones have been developed.
    Etiquette
    Cellphone etiquette has become an important issue with mobiles ringing at funerals, weddings, movies and plays. Users often speak at increased volume, with little regard for others nearby people. It has become common practice for places like libraries and movie theatres to ban the use of cell phones, sometimes even installing jamming equipment to prevent them.
    Media
    Cameraphones and videophones that can capture video and take photographs are increasingly being used to cover breaking news. Stories like the London Bombings, the Boxing Day Tsunami and Hurricane Katrina have been reported on by cameraphone users on news sites like NowPublic and photosharing sites like Flickr.
    Cellphone Features
    Cellphones are often packed with features that offer users far more than just the capability to send text messages and make voice calls. These may include internet browsing, music(MP3) playback, personal organisers, email, watch/alarm, built-in cameras, ringtones, security measures(e.g. pin codes), SIM blocks, games, radio, push to talk, infrared and bluetooth connectivity, and call registers.
    Network Features
    Though cellphones vary significantly from provider to provider, and even nation to nation(most noticeably in North America), all cellphones must generally accomplish the same tasks regardless. Cellphones must be connected to the system of landline phones. Cellphones must also be able to connect with each other just as easily, even if the two phones are not from the same mobile service provider. Consequently, all cellphone systems are comprised of two components; the handset, and the tower. The handset is the portable, referred to as the mobile phone, cellphone or a smartphone. The tower is a high-yield radio tower that the cellphones direct their radio communications to in order to connect to the network of telecommunications. It could also be a network of satellites.
    Network Working Process
    The Handset
    Handsets feature a low power transceiver that is typically designed to transmit voice and data, or analog audio only, up to a few kilometers under ideal situations to where the tower is located. The handset listens for an available tower. Once found, the handset informs that tower of its own unique identifier, and alerts the cellphone network that it is ready and standing-by to receive telephone calls. It then periodically repeats this information to the tower, and seeks out new towers over the duration it is powered on.
    The Tower
    Towers are large structures that feature a series of high power radio transmitters designed to broadcast their presence and availability, and relay communications to the mobile handsets. The tower features a much higher-powered radio transceiver array that allows it to provide a radio communications dialog with handsets dozens of kilometers away. The tower is connected to the landline telephone infrastructure by a high-capacity phone line, and may also be connected to a dedicated data line. The tower can then route calls between the mobile handsets it’s serving, and telephone calls over the landline. Because the tower tracks and relays what mobile handsets it is servicing, it can inform the mobile network provider so that al any given time a call to a cellphone can quickly be traced to the tower that is servicing that handset.
    The Data Stream
    Most cellphones dialog between the handset and the tower is comprised of a data stream of digitized audio. The technology driving this process can vary, and in nations with no standard or preference(such as the United States), many incompatible technologies exist. Not only do transmission standards potentially differ, but so do the radio frequencies. Some technologies include AMPS for analog, and TDMA, CDMA and GSM for digital communications. Though nations like the USA have generally avoided official standardization, most nations of the world have agreed upon the GSM data transmission protocol for cellphones, and a small range of possible frequencies that cellphones may operate on. Phones are classified based on the technology they use and the features they have.
选项 A、Y
B、N
C、NG
答案 A
解析 The main difference between cordless phones and cellphones is that cordless phones can only operate in a limited range．词汇线索为cordless phones，定位后找到文章首句括号内的部分：which acts as a telephone only within a limited range，则正确答案Y。
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