How does a SIM card work

SIM cards are an integral part of mobile phone technology and a Multi Network Sim like those from allow you to connect to your mobile phone provider and receive all the elements of your phone package, such as data allowance and call and text message allowances.

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The SIM card is made up of a base material and an IC Chip that holds all the authentication data. Once you insert the SIM card into your mobile device it will communicate with your mobile network. The card contains an International Mobile Subscriber Identity or (IMSI) which is linked to your account with your mobile provider and it is used to identify and authenticate you and your account.

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The SIM also holds encryption keys that ensure that the telephone calls, text messages and other data transmissions that you make are encrypted. This ensures that all activity between your mobile device, across your mobile network is protected with unauthorised access. It also contains information about the mobile network that your account is associated with and the type of network. For example it will identify whether you have 4G or 5G access and the subscription in terms of your data allowance and your call and text package.

If you travel abroad it is your SIM that will allow you to connect to a foreign mobile network by authenticating your device to this network. This is vital to take advantage of mobile roaming technology.