The SIM, Subscriber Identity Module, is a smart microprocessor chip for mobile phones used in all GSM and 3G networks (where it is called the USIM).
The SIM can also be used on other digital telephone networks such as IDEN and some versions of CDMA.
The SIM also stores your personal phone directories, messages, information on roaming across different networks and many other value-added voice and data services.
End-users are able to instantly access news, games, chat and dating services along with mobile payment applications with an easy to use interface.
It is not restricted by the handset make enabling operators to reach all of their customers.
Operator-centered services such as call completion and automatic handset configuration help them reduce their customer billing costs and increase their Average Revenue per User (ARPU).
The SIM card can add, delete and manipulate information within its memory, on top of sending and receiving data.
A SIM card can be replaced by users and slides easily into a slot within your phone or mobile device.A regular SIM measures 15 millimeters x 25 mm and a newer, smaller version of the SIM, called the micro SIM or 3FF SIM card is 12mm x 15mm.Originally designed to access mobile phone networks, it authenticates the subscriber and ensures the user is accurately billed for used airtime.The SIM is the final link in the chain between networks and end-users and no customer can connect to the network without their SIM.Network operators are able to communicate, download applications, and manage a SIM card remotely using Over-the-Air (OTA) technology.For example, network operators are able to update the SIM cards with new applications and services without requiring users to upgrade their handsets or visit a store location.