How does the SIM card work?

How does the SIM card work

You may be using your SIM card every day. However, if someone asks you how it works it will be difficult to explain. If you want to know how SIM cards work, keep reading below as we explore why a small card is so important to mobile users.

What is a SIM card?

Modern mobile phones come in two main types, namely Code Division Multiple Access (CDMA) and Global System for Mobile (GSM). Although CDMA phones do not require a SIM card, GSM models do67X and are likely to be the most popular of these two options.

In fact, the SIM card is a small card placed on the back of a GSM smartphone and the name SIM stands for Registration ID Module.

How does the SIM card work?

The SIM card contains a small chip that acts as its own small controller. It is made of silicone and is attached to gold or other metal to help it stay in touch with the phone. The chip contains a processor, memory and security circuits. Your phone reads the chip when you insert a SIM into it. Contains a card operating system and stores important information such as SMS messages and phone numbers.

All messages from your phone to the network are encrypted. The encryption key and the encryption key are stored on the SIM card. This provides communication privacy.

The SIM card chip also stores certain data such as the name of your service provider, the serial number of your card, your PUK code, the last dialed numbers and your PIN code.

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Your SIM card is also where International Mobile Subscriber Identity (IMSI) is stored and its authentication key. This key is provided by your carrier and connects your phone number with your device. This means that when someone dials your number, the call will go through the phone you have.

Procedure for unlocking SIM card

Once installed, your SIM card follows a verification process such as:

• First turn on your phone so that it can receive IMSI on the SIM card. This information is then sent directly to the network.

• The network searches for the IMSI verification key within its website.

• So the network generates a new phone number based on the verification key.

• Your SIM card is valid and you can now enjoy your phone and use it in the same way.

Once you have activated the prepaid SIM card, it is very easy to transfer it to another phone if you decide to switch phones. It is good to note that each SIM card comes with a unique identifier known as the Integrated Circuit Card Identifier (ICCID).

ICCID is literally recorded on the SIM card and contains three digits. There is a unique identification number for your account, a SIM card identification digit and a combination number for the other two numbers.

Most SIM cards come with a maximum capacity of 32KB to 128KB. If you want to transfer data such as SMS messages from one phone to another, you must remove the SIM card and insert it into the device from which you want to transfer data. After all, even after inserting a SIM card, you still need to worry about your network connection speed. In order to have a stable connection at all times, you will need to get yourself a mobile signal booster.

What about locked SIM cards?

When most of us encounter a locked phone we think that the SIM card is your fault. However, usually the phone is locked and not the SIM card itself.

GSM carriers have the ability to create software that locks securely to a specific network over a phone other than any other network. This means that the phone can only work if used with the same SIM card.

If you want a locked phone to access SIM cards from different networks, you must turn it on, but that is another matter.

Prepaid SIM cards

SIM cards work according to the payment system as you travel differently than a repeat contract or registration system. Prepaid SIM cards are cheaper than most recently and are useful for anyone who wants to avoid the cost of roaming overseas travel.

What is eSIM?

As SIM card technology continues to emerge, the industry is now moving to eSIM, a type of SIM card built into the phone. ESIM is enabled remotely by the service provider which means you do not have to install it in person.

Some phone companies already use SIM cards as part of the dual SIM setup. However, this option is only available to a few providers and will take some time before it becomes standard.


Although it is possible to use your phone without a SIM card, you cannot make calls or send messages without it. In fact, a smartphone device without a SIM card is like a stupid person. We hope this article has helped you to understand how SIM cards work to get the most out of them.