Sim Card PNG

Sim Card PNG

There are two types of mobile phones available to consumers today. GSM (Global System for Mobile) and CDMA (Code Division Multiple Access). While GSM phones work with a SIM card, CDMA phones do not need a SIM card.

SIM cards are small cards with a chip on it. GSM phones cannot connect to mobile networks without a SIM card. All critical information for connection is located on the card.

CDMA carriers maintain a list of all phones they allow to use on their network. Phones are tracked by ESN (electronic serial number) code, so no SIM card is needed. Once CDMA phones are activated, they can be connected directly to the corresponding network.

In the US, most mobile carriers use CDMA phones, with the exception of AT-T and T-Mobile. Worldwide, GSM is a much more popular technology.

How SIM Cards Work

Your SIM card contains not only which network to connect to, but also your "login information" that you need to connect to the network. So the SIM card is actually quite practical when changing your phones. Since your membership information is on the card, you can insert the card into a different phone and start using your phone immediately. On CDMA phones, this task is a little more difficult, because the identity of the phone is registered on the network.

Each SIM card has a unique identifier called ICCID. This code is both registered in the card and written on the card. They can store some data such as SIM cards, contact lists, SMS messages. Most have capacities ranging from 32 KB to 128 KB. Today, SIM cards are only used to connect to the mobile network, as SIM card storage space lags far behind what new mobiles offer.