Generally phones can be locked to accept only SIM cards with certain International Mobile Subscriber Identities (IMSIs) IMSIs may be restricted by: This is in contrast to a phone (retrospectively called SIM-free or unlocked) that does not impose any SIM restrictions.
Technical restriction built into mobile phones by phone manufacturers for use by service providers to restrict the use of these phones to specific countries and/or networksĪ SIM lock, simlock, network lock, carrier lock or ( master) subsidy lock is a technical restriction built into GSM and CDMA mobile phones by mobile phone manufacturers for use by service providers to restrict the use of these phones to specific countries and/or networks.
