Operated by the Global System for Mobile Communications network, a Subscriber Identity Module, SIM, card is a transportable microchip used to authenticate and identify users. By having an SIM card integrated within their mobile devices including phones and computers, users can handle, remove and insert their personal information from one device to another with great ease. This information includes his or her phone number, text messages, address book and other data.

Along with its easy access, the card offers great security with its encryption key that protects the phone’s transmissions, and can also be locked with the use of a PIN number. The SIM card also gives you a phone number and determines the phones available features based on the GSM network you choose. With all unlocked phones any SIM card can be used. On some networks, like the ones in the US, Canada, Australia, the UK and Poland, the phones only work with SIM cards from the specific carrier.

For carriers of GSM devices the use of SIM cards is mandatory. Printed on each card’s microchip there’s a unique number that needs to be given to the service provider for the SIM card to be activated. Since all of the user’s data is tied to the SIM card, it only needs to be activated once the person opens an account with a cellphone service provider..

SIM cards are especially beneficial when using mobile devices while traveling. An unlocked phone allows you to switch out SIM cards as you travel from one country to another. This is a big money saver, giving you cheap pay-as-you-go calls. Every country has various service providers, all of which sell their own SIM cards. In Europe, SIM cards are sold at train stations and airports, allowing immediate access to the European rates for calling and texting.