What is SIM card?
[[File:GSM SIM card evolution.svg|thumb|Different sizes of SIM cards. From left to right, they are full-size, mini SIM, micro SIM, and nano SIM.]] A '''SIM card''' (subscriber identity module) is a [[smart card]] that is used in [[mobile phone]]s, to identify the client. SIM stands for subscriber identity module. A SIM card has a [[microchip]], and its use is protected by a [[PIN]]. When the phone is powered on, an international mobile subscriber identity number (IMSI) is broadcast. The microchip is also needed for some [[encryption]] and [[decryption]]. The SIM card and the device that it is used in (the mobile phone) are often referred to as the ''Mobile station''. SIM cards come in different sizes. Full-size SIM cards, which are about the same size as a [[credit card]], are not used in phones anymore. Most [[Smartphone|smartphones]] use either micro SIM or nano SIM cards, but older ones use mini SIM. [[Category:Mobile phones]]