A SIM card stores network and subscriber information for mobile devices, identifying users on a network and providing access to services. It contains ICCID numbers and an authentication key for network security. SIM cards come in three sizes, with Mini and Micro SIMs being the most common.
A subscriber identity module, otherwise known as a SIM, is a circuit that stores network information and subscriber information for a mobile device, such as a cell phone or computer. The subscriber identity module works to uniquely identify an individual on the specific network, validating their right to use the network along with other specific information such as passwords and services to which the user is subscribed. Without a functioning subscriber identity module, the associated device’s network capabilities are therefore crippled.
Think of a subscriber identity module like a ticket that allows the end user to see a movie or show. It gives them access to the theater, the mobile network they connect to. It does this by storing ICCID (Integrated Circuit Card Identifier) numbers. IC card identifier numbers consist of a combination of the identifier for the network operator, such as the specific mobile phone company, the country code for the end user’s region, the individual account number of the end user and a check digit. A check digit is a validation number, much like the security code on the back of a credit card.
In addition to this, a SIM also contains an authentication key for the specific mobile network to which the end user connects. It’s kind of like a wireless security code for wireless networks, ensuring that not everyone can get in and steal bandwidth from your network. Using a combination of codes, such as an ICCID code and an authentication code, ensures that SIM cards are not easily hacked.
Subscriber ID Module cards come in three main formats. The first size is about the same size as a credit card; but as mobile devices have continued to shrink in size, this form factor has largely been abandoned. Today, the most common types of SIM cards are Mini and Micro SIM. Mini SIMs are just 25 millimeters (just under an inch) by 15 millimeters (about 0.6 inch) in size. Micro SIMs measure just 15 millimeters (0.6 inches) by 12 millimeters (about half an inch), making them useful for smaller types of mobile electronic devices.
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