It is a software capability built into GSM phones by mobile phone manufacturers. Network providers use this to restrict the use of these phones to specific countries and network providers.
FAQs
Unlocking your cell phone has multiple benefits : It increases the resell value and marketability of your phone by not restricting the resell to a specific carrier, it allows the handset to work worldwide (See What networks are compatible with my phone ?), it eliminates roaming charges by allowing you to switch to a local carrier in the local region.
The Digital Millennium Copyright Act, introduced an exemption on November 27, 2006 specifically permitting unlocking of cellular devices. The exemption was scheduled to expire on October 27, 2009, but was extended on an interim basis, because the Register of Copyrights had not yet completed its triennial review of DMCA exemptions. In July 2010, the Librarian of Congress extended the DMCA exemption for another 3 years.
When the purchase price of the mobile phone to the consumer is subsidized with revenue from subscriptions, operators must recoup this investment before a subscriber terminates service. In order to secure their investments, GSM network providers implements a software feature called SIM Lock on the handset to prevent usage outside their network. Such subsidies are worth more than several hundred US dollars and in that’s why carriers also charge an early termination fee; another form to recoup the subsidy investment.
Insert a SIM Card from a different carrier than the one your handset is using. When power up is complete the handset will display a message like those below if it SIM locked :
– Enter Subsidy Code
– Enter Unlock Code
– Incorrect Sim Card
– Insert Correct Sim Card
– Invalid Smart Chip
– Phone Restricted
– Sim Network Unlock Code
– Sim Network Unlock Pin
– Special Code Required
– Wrong Sim Card
– Network Lock Control Key
– Sim Password
– Incompatible Sim
– Enter Subsidy Pin
