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Now showing the answer to your question in category: General
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| Question: What's a SIM? |
Answer: A subscriber identity module (SIM) is a smartcard securely storing the key identifying a mobile subscriber. SIMs are most widely used in GSM systems, but a compatible module is also used for UMTS UEs (USIM) and IDEN phones. The card also contains storage space for text messages and a phone book.
From the technical point of view the SIM is a microcomputer, which performs all necessary operations based on informations stored inside it. It consists of a CPU, ROM, RAM, EEPROM and I/O circuits.
Since the SIM card slot is standardized (by the GSM11.11 standard), a subscriber can easily move their wireless account and phone number from one handset to another. This will also transfer their phone book and text messages. Similarly, in theory, a subscriber can change carriers by inserting a new carrier's SIM card into their existing handset. However, this is not always possible, because most carriers SIM-lock the phones that they sell, preventing rival carrier's cards being used.
Source: Wikipedia http://en.wikipedia.org/wiki/SIM
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