When installed into your mobile phone, the Subscriber Identity Module سیم کارت a smart card chip the size of a postage stamp, serves as the intelligence source for many forms of communication. A small card with an embedded integrated circuit is known as a smart card, or integrated circuit card (ICC). Despite having a wide range of applications, ICCs can be divided into two major groups. The first is a non-volatile memory card that solely has storage components, and the second is a type of microprocessor circuitry made up of memory or microprocessor parts.
The SIM is a microprocessor device that has memory storage capabilities, and it houses all of the specific data related to your account. It keeps track of your identity and gives the network access to it in the form of your service provider account number. The memory on the currently available SIM card, which ranges from 16 to 64 kilobytes, is used to store your own phone numbers for calls and texts, as well as additional value-added services. The ability to download a photo, an MP3 music, or even a mobile ringtone is frequently offered as a value-added feature. These data or information are stored in the memory space on your SIM card so you can access them as needed. Larger memory areas are required to store high resolution images, huge MP3 files, and to stream live video.
The Universal Mobile Telecommunications System is a third-generation mobile phone technology (UMTS). A Universal Subscriber Identity Module (USIM) is a programme that runs on a Universal Integrated Circuit Card for UMTS mobile telephony (UICC). Another kind of chip smart card used in GSM and UMTs is the UICC. This card, in contrast to SIM, has a large memory and can store a few kilobytes of data. The smart chip’s storage space needs to be expanded as more services become available. In a GSM context, the UICC contains a SIM application, whereas the USIM application is used in a UTMS environment. Your SIM is identifiable by its International Circuit Card ID in a unique way (ICCID).
After entering into a contract with the service provider, SIM cards are made accessible on a subscription basis. They can be purchased either on a pay-as-you-go basis, where you receive monthly invoices, or as a pre-paid subscriber, where you pay a set fee up front for the service you choose. Depending on the kind of agreement you sign, this may occur.
Your smartphone may also support two SIM cards. All you have to do is get a dual SIM cover for the model of your mobile phone from your dealer. This provides a number of benefits, including the ability to utilise two SIM cards—one for personal usage and the other for business—in a single mobile device.
The majority of the time, the SIM may be taken out of a mobile phone, allowing you to carry your data plan and mobile subscription through many GSM-compatible mobile phones of your choosing. The possibility exists that the mobile phone with the SIM card inside will end up lost, stolen, or misplaced. The earliest you can do is ask the service provider to deactivate that SIM, explaining why, and then get a new SIM card for your new phone. The service provider may charge you a fee for providing you with a duplicate SIM card.
The majority of mobile phones are “SIM unlocked,” allowing them to be used with any SIM card from any provider worldwide. Numerous mobile phones are “SIM locked” by the service provider, usually for the duration of the contract time, in accordance with the terms of the agreement you sign. These phones won’t function as before with a different SIM card.
The SIM card’s internal circuitry contains data regarding the service plan that you have selected as a subscriber. The SIM also stores network information in the form of your current area location (LAI) details. When you turn on your mobile device, you’ll discover that the software inside looks for the network you’re signed up for and locks you onto that service provider. It accomplishes this by retrieving the required information from your SIM and looking for the LAI it was in.
Your mobile phone’s SIM card, which contains an International Mobile Subscriber Identity, serves as a means of identification (IMSI). IMSI, which is kept in the SIM, is the number that uniquely identifies each user of the GSM and Universal Mobile Telecommunications System (UMTS) networks. This number is sent to the network when a call is made and is used to obtain further information from the Home Location Register (HLR) or as made available in the Visitor Location Register (VLR). All of the subscriber’s information that is necessary for managing mobility and handling calls in the VLR-controlled region is stored in the VLR. The Temporary Mobile Subscriber Identity (TMSI), which is used relatively frequently, is sent rather than the IMSI due to security concerns.
The Personal Identification Number (PIN) number, a 4–8-digit password you choose and input each time you want to access your mobile phone, is stored on the SIM card for security reasons. Additionally, there is a PIN2 that may be used with GSM II applications to access the mobile’s more sophisticated functions. When you input the password incorrectly, the system gives you three attempts before the SIM card locks and you require a Personal Unblocking Key (PUK) from your network provider to unlock your phone. PUK2 serves the same function as PUK but with PIN2.
