* SIM cards and cell phone restrictions
As you may know, the business model for delivering cellular phones and services in the U.S. is for network operators to heavily subsidize the cost of the mobile phones they sell alongside their services. In return, they tie you into a service contract, usually for two years, and reserve the right to limit your freedom in using certain phone capabilities and other carriers’ wireless network services.
In other words, carriers in the U.S. “lock” the subsidized phones they sell so the phones can be used only on their networks. An unlocked phone, by contrast, isn’t tied to a specific carrier, so it can be used with network services delivered by different operators.
The locking/unlocking of phones is mostly relevant to the GSM-based cellular environment. GSM networks are pervasive worldwide (offering service in more than 200 countries) and most users require the mobile network services of one or more additional providers when they travel globally.
The “brain” of a GSM phone is the subscriber identity module (SIM). When a phone is unlocked, its SIM card can be removed and replaced with one that associates the user to a different carrier. To get unlocked phones and use SIMs, you have to find a store – virtual or otherwise – that sells unlocked phones, and you’ll likely have to pay full retail price. However, check your carrier contract. Some carriers have a provision that after a specified length of service, they will unlock the phones for you.
With unlocked phones, companies can change carriers without having to change out all their users’ phones. In addition, IT departments can buy SIMs that work in frequently visited locations in bulk, and users can be outfitted for mobile communications in their destination city before they leave town.
Without an unlocked phone, on the other hand, traveling users will need another device that works locally in their destination city.
