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What are SIM cards?

Updated: Oct 15, 2019


You can think of a SIM card like an ID card for phones! SIM cards create an identity with data like phone numbers, network, personal security keys, contacts and stored text messages.


Not all SIM cards work the same, there are two distinct types; GSM (Global System for Mobile) and CDMA (Code Division Multiple Access). The most commonly used type amongst network carriers(like T-Mobile and AT&T) is GSM .

There are different sizes of SIM cards in the market, you’ll see the standard SIM measuring 25x15mm and commonly used in basic phones and older. Here are some other specs:

  • Micro SIM cards measure 15x12mm, and are more likely to be found in phones from the 2010s and up.

  • Nano SIM cards measure 12.3x8.8mm and are used in newer smartphones.

  • eSIM, or embedded SIM’s, measure 6x5mm, and has the SIM card installed in the phone already. eSIM’s are activated remotely by the network carrier.

The biggest advantage of using a SIM card is that it can easily be switched from phone to phone, you can have multiple lines and keep your local number!


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- Zynet Inc.

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