What is a SIM card?

Subscriber Identity (SIM) is a portable memory chip used mainly in mobile phones that work in the global network for mobile communication (GSM). These cards hold the account holder's personal data, including his phone number, directory, text messages and other data. When a user wants to change phones, he can usually easily remove the card from one handset and put it in another. SIM cards are convenient and popular with many users and are a key part of the development of mobile phone technology.

SIM card activation

Since all user data is tied to a SIM card, it must be activated when a person opens an account with a mobile phone provider (also called a carrier). Each card has a unique number printed on a microchip that the carrier needs to activate. In most cases, the phone owner can switch to the carrier's website and enter this number in the appropriate tool, or call the Service Priser directly from another phone to turn on. SIM cards jSOU associated with a particular carrier and can only be used with the service plan from this carrier.

Exchange phones

One of the biggest advantages of the SIM card is that it is easy to remove from one mobile phone and use any other compatible phone to call. This means that if a user wants to buy a new handset, he can quickly activate it by inserting his old SIM card. The user's phone number and personal data are made on the card, so there is no need to do anything else to transmit this information. However, most phone applications (applications) are stored in the phone memory or secure digital (SD) card, so they will not be transferred to the new headphone.

Some mobile phone carriers lock their phones; This means that they will only work with SIM cards from this carrier. This is special common in the US where service providers sell headphones with discountIn exchange for consumers signing a long -term service contract. However, the pluch can be unlocked by the correct code, although the exact process varies according to the manufacturer and the model. Any SIM card can be used with an unlocked phone. Phones without a card or with a text that is not compatible can usually be used only for emergency calls.

Prepaid SIMS

There are also prepaid SIM cards that allow you to use a phone with a prepaid carrier or unlocked phone without a long -term contract. This type of card is useful for people who do not want to be tied to one carrier or who want to test service providers before committing. This is particularly useful for international travelers who can buy a local SIM card to use their phone abroad. This allows the user to maintain the same phone - with applications and other settings that are stored in it - without paying International Roaming fees from the carrier back home. He also gives the passenger to the local teLefon number, so it's cheaper for people to call travelers from the same country.

SIZE SIX cards

SIM cards are made in three different sizes to suit different devices. Most phones use mini-SIM or micro-SIM cards that are relatively small-mini is 25 mm x 15 mm (0.98 V 0.59) and micro is 15 mm to 12 mm (0.59 V 0.47 inches). Full -size cards are much larger, 85.6 mm of 53.98 mm (3.37 V 2.13 inches) and are too large for most phones. However, all cards are only 0.76 mm (0.03 inches) and microchips contacts are in the same arrangement. This means that for the right adapter, smaller cards can be used on larger devices.

Security

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SIM card offers security for both user data and calls. The cards can be locked, which means only someone who has the right personal identity can use the IFICATION (PIN) number. If the phone is stolen, the thief cannot use the locked simu

In addition to ito My card has a secret authentication code and an encryption key that protects your phone transmissions. Although it is possible to "clone" the mobile phone in the GSM network and so steal the service, it is much more difficult than cloning the phone in the network of competing code division (CDMA). Given how encryption information is transmitted to the carrier, it is usually necessary to have physical access to the SIM card to copy.

Other mobile phone technologies

phones that work on the CDMA network do not use SIM cards; Instead, most save the phone number and other identification data in the handset itself. Although it can be less advantageous for users, CDMA is the most common in the US, where phones are usually strongly subsidized and users may have less motivations to frequently switch phones. In addition, some carriers, mostly in Asia, use their own removable card format, called the reophable identification module (Ruim).

Since technology is changing, however, more providerMobile phones upgrade to 3GPP long -term development (LTE), which is based on GSM technology. This means that some kind of SIM card is likely to be required for devices that use this network.