|
Mobilephone manufacturers include Audiovox, BenQ-Siemens, High Tech
Computer Corporation, Fujitsu, Kyocera, 3G, LG, Motorola, NEC, i-mate,
Nokia, Panasonic (Matsushita Electric), Pantech Curitel, Philips, Sagem,
Samsung, Sanyo, Sharp, Siemens SK Teletech, Sony Ericsson, T&A Alcatel,
T-Mobile, and Toshiba.
Invented in 1997, the
camera phone is now 85% of the market. Mobile phones also often have
features beyond sending text messages and making voice calls—including
Internet browsing, music (MP3) playback, personal organizers, e-mail,
built-in cameras and camcorders, ringtones, games, radio, Push-to-Talk
(PTT), infrared and Bluetooth connectivity, call registers, ability to
watch streaming video or download video for later viewing, video call and
serve as a wireless modem for a PC.
In most countries, including Europe, Japan, India, the person receiving a
cellular phone call pays nothing. However, in Hong Kong, Canada, and the
United States, one can be charged per minute. In the United States, a few
carriers are beginning to offer unlimited received phone calls.
For example as of December 2006, Sprint now
has 4 plans under "Sprint Free Incoming Plans" section of their website,
although the restriction is the receiving phone must be on the Sprint PCS
network. For the Chinese mainland, it was reported that both of its two
operators will adopt the caller-pays approach as early as January 2007.
Mobile phones and the
network they operate under vary significantly from provider to provider, and
nation to nation. However, all of them communicate through electromagnetic
microwaves with a cell site base station, the antennas of which are usually
mounted on a tower, pole, or building.
The phones have a low-power transceiver that transmits voice and data to the
nearest cell sites, usually 5 to 8 miles (approximately 8 to 13 kilometres)
away. When the cellular phone or data device is turned on, it registers with
the mobile telephone exchange, or switch, with its unique identifiers, and
will then be alerted by the mobile switch when there is an incoming telephone
call. The handset constantly listens for the strongest signal being received
from the surrounding base stations. As the user moves around the network, the
mobile device will "handoff" to various cell sites during calls, or while
waiting (idle) between calls it will reselect cell sites.
|
