SIM card

A SIM card (subscriber identity module) is a smart card that is used in mobile phones, 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, its 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 smartphones use either micro SIM or nano SIM cards, but older ones use mini SIM.
Embedded SIM cards

alt=Comparison of SIM card sizes|thumb|Evolution of SIM cards. An eSIM is not removable.Later, so called embedded SIM cards were developed. These are usually referred as eSIM. The work  the same way as the older SIM cards, but they allow to store more than one profile. Only one profile can be active at the same time. This makes it possible to sell phones without a profile. In such phones, a profile needs to be loaded onto the eSIM before the phone can be used. As the eSIM is an integrated circuit, such phones no longer need a physical slot for a SIM card.
Category:Mobile phone standards