A SIM card 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, 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 smartphones use either micro SIM or nano SIM cards, but older ones use mini SIM.
Types of SIM cards[change | change source]
- Full SIM: No longer in use, the original SIM card was developed in the 1990s and measured 86x54mm. Despite the large size, virtually all of it was a plastic card - the actual contact surface was the same as later cards.
- Mini-SIM: Because the full-size SIM is no longer used, these days this is often thought of as the full or standard SIM. It measures 25x15mm and the contact surface is surrounded by a large segment of plastic.
- Micro-SIM: A micro-SIM has the exact same contact surface but is smaller (15x12mm) because the plastic is trimmed away, leaving a card almost entirely of just the contact surface.
- Nano-SIM: This is the smallest SIM format in use today. It has a smaller contact surface, making it physically incompatible with older phones that expect a micro-SIM. It measures 12.3x8.8mm.
- eSIM: An embedded SIM, or eSIM, is a new, emerging format in which the SIM is embedded directly into the device and is therefore not removable. Although not widely used, the advantage of an eSIM is that it allows you to change phones without transferring SIM cards; the mobile operator transfers the account information remotely.
References[change | change source]
- "A guide to SIM cards, the small chips that connect your phone to a cellular network". Business Insider. Retrieved 2021-09-13.