It also contains RAM (random access memory) and ROM (read-only memory). These SIM cards vary in size but all have the functionality for both the identification and authentication of the subscriber’s phone to its network and all contain storage for phone numbers, SMS, and other information, and allow for the creation of applications on the card itself.Ī SIM card contains a processor and operating system with between 16 and 256 KB of persistent, electronically erasable, programmable read-only memory (EEPROM). But today we are using smartphones that use micro-SIM, which is smaller than mini-SIM. The mini-SIM card, which is about one-third the size of a credit card. As technology developed, the cell phone began to shrank in size and so did the SIM card. The first SIM card was about the size of a credit card. If the SIM and USIM application are running on the same UICC, then they cannot be working simultaneously. A USIM has a unique feature in that it allows one phone to have multiple numbers.

USIMs are enhanced versions of present-day SIMs, containing backward-compatible information. The UICC card accepts only 3G universal mobile telecommunications service (UMTS) commands. Basically, the ICC deployed for 2G networks was called a SIM and the UICC smart card running the universal subscriber identity module(USIM) application. All cell phones are expected to incorporate some type of identity module eventually, in part because of this useful property. It is a physical entity and can be either a subscriber identity module (SIM) or a universal integrated circuit card (UICC).Ī SIM can be removed from a cellular handset and inserted into another it allows users to port identity, personal information, and service between devices. It also known as an integrated circuit card (ICC), which is a microcontroller-based access module. The SIM (subscriber identity module) is a fundamental component of cellular phones.

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