What Is A SIM Card Really?

December 19th, 2008

Subscriber Identity Module (SIM) card is a small memory chip that stores network specific data used to recognize the subscribers using mobile telephony devices on the network. Each SIM card stores a unique International Mobile Subscriber Identity (IMSI) and Key Identification (KI). The IMSI identifies the subscriber’s network and account. KI also known as authentication key is a password for IMSI. SIM cards are used with carriers that operate on the Global System for Mobile Communication (GSM) network.

The other carrier specific data stored in SIM cards includes SMSC (Short Message Service Center) number, Service Provider Name (SPN), Service Dialing Numbers (SDN), Value Added Service (VAS) applications and Advice-Of-Charge parameters. Apart from carrier specific data, SIM cards also store cell phone numbers, rate plan, text messages and other data.

Some Facts About SIM Cards

SIM cards prevent subscriber’s calls from being traced and phone from being stolen due to its very beneficial verification and encryption abilities.

SIM cards are not used with CDMA (Code Division Multiple Access) cell phones and CDMA carriers in most countries.

SIM cards make it easy to change phones, you just need to remove the SIM card from one phone and insert it into another.

SIM cards are like mini hard disks as the data stored in SIM cards can easily be switched between different phones.

SIM cards are globally identified by their Integrated Circuit Card ID (ICC-ID). The SIM card contains this ID in its memory as well as on its body.

International travelers can replace their SIM card when visiting other countries with the local SIM cards to save international roaming charges, but you must have an unlocked cell phone working on the correct frequency band.

There are some CDMA providers that use a type of “SIM card”. One company would be the Mike network by Telus. It’s not really a SIM card since they are still using the CDMA network. If you are looking for any unlocked cell phone don’t hesitate to check out puremobile.ca