A mobile phone (also known as a handphone,^[1] wireless phone, cell phone, cellular phone, cellular telephone or cell telephone) is a long-range, electronic device used for mobile voice or data communication over a network of specialized base stations known as cell sites. In addition to the standard voice function of a mobile phone, telephone, current mobile phones may support many additional services, and accessories, such as SMS for text messaging, email, packet switching for access to the Internet, gaming, Bluetooth, infrared, camera with video recorder and MMS for sending and receiving photos and video, MP3 player, radio and GPS. 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 is satellite phones).

A mobile phone proper typically has a telephone keypad, more advanced devices have a separate key for each letter. Some mobile phones have a touchscreen.

 

Features

Mobile phones often have features beyond sending text messages and making voice calls, including call registers, GPS navigation, music (MP3) and video (MP4) playback, RDS radio receiver, alarms, memo and document recording, personal organiser and personal digital assistant functions, ability to watch streaming video or download video for later viewing, video calling, built-in cameras (3.2+ Mpx) and camcorders (video recording), with autofocus and flash, ringtones, games, PTT, memory card reader (SD), USB (2.0), infrared, Bluetooth (2.0) and WiFi connectivity, instant messaging, Internet e-mail and browsing and serving as a wireless modem for a PC, and soon will also serve as a console of sorts to online games and other high quality games.

Some phones includes touchscreen.

The total value of mobile data services exceeds the value of paid services on the Internet, and was worth 31 billion dollars in 2006 (source Informa).^{[citation needed]} The largest categories of mobile services are music, picture downloads, videogaming, adult entertainment, gambling, video/TV.

Nokia and the University of Cambridge are showing off a bendable cell phone called Morph.^[8]

SIM card

In addition to the battery, GSM mobile phones require a small microchip, called a Subscriber Identity Module or SIM Card, to function. Approximately the size of a small postage stamp, the SIM Card is usually placed underneath the battery in the rear of the unit, and (when properly activated) stores the phone's configuration data, and information about the phone itself, such as which calling plan the subscriber is using. When the subscriber removes the SIM Card, it can be re-inserted into another phone and used as normal.

Each SIM Card is activated by use of a unique numerical identifier; once activated, the identifier is locked down and the card is permanently locked in to the activating network. For this reason, most retailers refuse to accept the return of an activated SIM Card.

Those cell phones that do not use a SIM Card have the data programmed in to their memory. This data is accessed by using a special digit sequence to access the "NAM" as in "Name" or number programming menu. From here, one can add information such as a new number for your phone, new Service Provider numbers, new emergency numbers, change their Authentication Key or A-Key code, and update their Preferred Roaming List or PRL. However, to prevent someone from accidentally disabling their phone or removing it from the network, the Service Provider puts a lock on this data called a Master Subsidiary Lock or MSL.

The MSL also ensures that the Service Provider gets payment for the phone that was purchased or "leased". For example, the Motorola RAZR V9C costs upwards of CAD $500. You can get one for approximately $200, depending on the carrier. The difference is paid by the customer in the form of a monthly bill. If the carrier did not use a MSL, then they may lose the $300–$400 difference that is paid in the monthly bill, since some customers would cancel their service and take the phone to another carrier.

The MSL applies to the SIM only so once the contract has been completed the MSL still applies to the SIM. The phone however, is also initially locked by the manufacturer into the Service Providers MSL. This lock may be disabled so that the phone can use other Service Providers SIM cards. Most phones purchased outside the US are unlocked phones because there are numerous Service Providers in close proximity to one another or have overlapping coverage. The cost to unlock a phone varies but is usually very cheap and is sometimes provided by independent phone vendors.

Having an unlocked phone is extremely useful for travelers due to the high cost of using the MSL Service Providers access when outside the normal coverage areas. It can cost sometimes up to 10 times as much to use a locked phone overseas as in the normal service area, even with discounted rates.

For example, in Jamaica, an AT&T subscriber might pay in excess of US$1.65 per minute for discounted international service while a B-Mobile (Jamaican) customer would pay US$0.20 per minute for the same international service. Some Service Providers focus sales on international sales while others focus on regional sales. For example, the same B-Mobile customer might pay more for local calls but less for international calls than a subscriber to the Jamaican national phone C&W (Cable & Wireless) company. These rate differences are mainly due to currency variations because SIM purchases are made in the local currency. In the US, this type of service competition does not exist because some of the major Service Providers do not offer Pay-As-You-Go services. [Needs Pay-As-You-Go references, rumored T-Mobile,Verizon provide one, AT&T does not as of 12/2008]

Terminology

Related non-mobile-phone systems

Car phone 

A type of telephone permanently mounted in a vehicle, these often have more powerful transmitters, an external antenna and loudspeaker for handsfree use. They usually connect to the same networks as regular mobile phones.

Cordless telephone (portable phone) 

Cordless phones are telephones which use one or more radio handsets in place of a wired handset. The handsets connect wirelessly to a base station, which in turn connects to a conventional land line for calling. Unlike mobile phones, cordless phones use private base stations (belonging to the land-line subscriber), and which are not shared.

Professional Mobile Radio 

Advanced professional mobile radio systems can be very similar to mobile phone systems. Notably, the IDEN standard has been used as both a private trunked radio system as well as the technology for several large public providers. Similar attempts have even been made to use TETRA, the European digital PMR standard, to implement public mobile networks.

Radio phone 

This is a term which covers radios which could connect into the telephone network. These phones may not be mobile; for example, they may require a mains power supply, they may require the assistance of a human operator to set up a PSTN phone call.

Satellite phone 

This type of phone communicates directly with an artificial satellite, which in turn relays calls to a base station or another satellite phone. A single satellite can provide coverage to a much greater area than terrestrial base stations. Since satellite phones are costly, their use is typically limited to people in remote areas where no mobile phone coverage exists, such as mountain climbers, mariners in the open sea, and news reporters at disaster sites.

References