In the area of mobile communications SIM is an acronym for Subscriber Identity Module, which is a memory chip that stores information about the carrier, the manufacturer, and the user of a mobile device (typically, a cell phone). A SIM card is typically a credit-card sized board that holds the SIM. SIM cards are used on mobile telephony devices, which can include tracking assets and computers as well as mobile phones. Users can move a SIM card from one mobile phone to another mobile phone or to a computer that operates as a broadband telephony device.
A SIM card stores information about the carrier (a unique International Mobile Subscriber Identity), which contains a mobile country code (3 digits), the mobile network code (2 digits), and the mobile station identification number (10 digits). SIM cards also have an Issuer identification number (maximum of 7 digits), which includes a major industry identifier (the number 89 for telecommunications), a country code (1 to 3 digits), and an issuer identification number (2 to 4 digits). Finally, SIM cards have an individual account identification number and a parity check digit.
SIM cards are used with carriers that operate on the GSM (Global System for Mobile communcation) network.