TABLE OF CONTENTS GSM mobile devices (also called mobile stations) are voice and/or data input and output devices that are used to communicate with a radio towers (cell sites). GSM end user devices include removable subscriber identity modules (SIMs) that hold service subscription information. The common types of available GSM devices include mobile telephones, PCMCIA cards, embedded radio modules, and external radio modems.
A subscriber identity module (SIM) is an "information" card that contains service subscription identity and personal information. The SIM card contains at least two numbers that identify the customer; the international mobile subscriber identity (IMSI) and a secret authentication key number K.
The SIM contains a microprocessor, memory and software to hold and process information that includes a phone number, billing identification information and a small amount of user specific data (such as feature preferences and short messages.) This information can be stored in the card rather than programming this information into the phone itself. A SIM card can be either credit card-sized (ISO format) or the size of a postage-stamp (Plug-In format). SIM cards can be inserted into any SIM ready communication device.
Access to a SIM card usually requires the use of a personal identity number (PIN) to restrict access to the SIM card to people who know the code. SIM cards may also be locked to the communication device by a SIM lock code (the service provider only knows the SIM lock code).
The SIM lock code ensures that a communication device will...
