When you dial a phone number and the person whom you have dialled receives it. The SIM card which you have inserted into your device does all the Magic! SIM stands for Subscriber Identity Module and is a very very small computer.
It does a variety of works that are essential to keep your phone working. The most important function is that it identifies you as genuine owner of the subscription. So when you call, message or share pictures the SIM card tells the phone which network to use and also tells your network to bill you for the services you use.
A SIM is made of Silicone and plated with gold and other metals to help it keep contact with the phone. The chip inside contains a processor, memory and security circuits. Your device reads the chip when SIM is in it. It contains the operating system for the card.
SIM card chip
The most basic types of information stored on your chip are your international Mobile Subscriber Identity and a 128 bit key called Ki(Key Identification). Those are basically your login and passwords like card's unique serial number, name of your cellular carrier, the PIN (Personal Identification Number) and a PUK code from your carrier to block or unblock a number.
Inside SIM card
All phones use the same chip but the plastic frame around it comes in different sizes.
- MINI SIM: This size used to be the standard for many years from 1996 till present and is the most common size. (25 x 15)mm
- MICRO SIM: Began to be used from 2010 and the size is smaller than MINI SIM. (15 x 12)mm
- NANO SIM: Introduced in 2013, it's size is even smaller than micro SIM and is 10% thinner. (12.3 x 8.8)mm
- Nowadays, eSIM (embedded SIM) are used in latest phones.
These are some of the facts about the small chip that does wondering things! Thank you for reading.
WRITTEN BY
NIDHI PATEL
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