Some mobile phones are designed for use stored a Subscriber Identification Module (SIM) or microchip subscriber data. The SIM card is issued by a vehicle and mobile services by activating any phone into which it fits. A locked phone can, however, that a SIM card of a particular society. When the phone is unlocked, you recognize a SIM card from any provider. Crash is a software environment that maintains the cell phone loyal to an airline.

In areas such as the United States, where telephone companies are offering free or discounted phones detailed plans usually closed and can not with other operators. Companies say it is necessary to subsidize the cost of the phones. After a while, a company can agree to unlock cell phones upon request, may pay a fee. Because of the property can sometimes locked phones is installed, the phones can not always work correctly with other carriers, even when open.

From the perspective of consumers, businesses and defeats of the practice of locking phones property settings many benefits of mobile SIM card.Complaints conducted by the American watchdog group Foundation on a complaint filed in California in June 2004 for the taxpayer and consumer rights (FTCR).Ideally, the phones need to be left open, or at least unlocked after the first contract.

One way is to get an unlocked phones without proprietary settings buy from a third party in its original form, open state. The disadvantage is that the price is often close to full version. Some consumers may be difficult in practice, a lot of money for a phone that will distribute a free map. The third advantage is that cell phones work equally well with any carrier, unlocked using SIM cards.