Subscriber Identity Module
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- SIM redirects here; for other uses see Sim (disambiguation)
A Subscriber Identity Module (SIM) is a smart card roughly the size of a postage stamp that securely stores the key identifying a mobile phone service subscriber, as well as subscription information, saved telephone numbers, preferences, text messages and other information. The equivalent of a SIM in UMTS is a Universal Subscriber Identity Module (USIM).
There are SIMs available in many storage sizes, the biggest being the 128 KiB sim, while the 64 KiB sim is most prevalent.
The SIM stores network state information such as its current Location Area Identity (LAI). If the handset is turned off and back on again it will take data off the SIM and search for the LAI it was in. This saves time by avoiding having to search the whole list of frequencies that the telephone normally would. Each SIM is uniquely identified by its ICCID (International Circuit Card ID).
SIM cards identify users uniquely by holding an International Mobile Subscriber Identity.
Japan's PDC system also specifies a SIM, but this has never been implemented commercially. The specification of the interface between the Mobile Equipment and the SIM is given in the RCR STD-27 annex 4. The Subscriber Identity Module Expert Group was a committee of specialists assembled by the European Telecommunications Standards Institute (ETSI) to draw up the specifications (GSM 11.11) for interfacing between smart cards and mobile telephones. In 1994, the name SIMEG was changed to SMG9.
In July 2005, the Finnish government announced that a Citizen Certificate - a government-guaranteed 'electronic identity' included in a SIM card - would be made available to every individual resident in Finland before the end of 2005, allowing mobile phone users to access e-services on the move. The Citizen Certificate has been described as "basically an e-ID card that will be compatible with several hardware devices, such as mobile phones, PDAs, personal computers, Digital TV sets, and public web kiosks". [1]
The use of SIM card is mandatory in the GSM world, whereas the SIM (RUIM) is not very popular in the CDMA world.
W-SIM is a SIM card which also integrates core cellular technology into the card itself.
[edit] SIM card reader / writer
A SIM card reader / writer (or simply reader) is a device that allows the contents of a SIM card to be edited. Several of these are available as consumer devices that connect to USB ports on computers.
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