What does locked or unlocked on a cell phone mean?

Written by eric dontigney
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What does locked or unlocked on a cell phone mean?
Mobile phones can be locked or unlocked. (Jupiterimages/Photos.com/Getty Images)

Cellular service plans often provide the purchaser with a free or dramatically discounted phone. The trade-off customers accept is that most carriers provide locked phones. In essence, this means the cellular service provider makes an adjustment to the phone that only allows it to operate with that provider's network. Unlocked phones, on the other hand, work with any network that supports the phone technology.

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Cellphones operate on either the global system for mobile communications or the code division multiple access systems.GSM and CDMA allow for voice and data transfer services. Carriers activate and control user information remotely on CDMA phones. Unlike CDMA phones, GSM phones employ a subscriber identity module card that carries user information, such as the telephone number and available features.Users can transfer a SIM card from one GSM phone to another, taking all the user information with it. The issue of locked or unlocked phones centres on GSM phones due to the simplicity of SIM card transfers.

GSM Locked And Unlocked

GSM service providers employ a carrier lock or SIM lock to prevent users from switching SIM cards. In essence, the service provider adds a locking code to the phone that prevents it from working with any SIM card not issued by the service provider. A GSM phone without a SIM lock will work with any SIM card. This proves especially helpful to users that frequently travel abroad, as it allows the user to cut down on international roaming charges by employing prepaid SIM cards from local service providers.

CDMA Locked And Unlocked

CDMA phones store a variety of information in the phone itself, including information about the carrier, the user and available features. Part of the programming in CDMA phones from service providers prevents the phone from working with other CDMA providers by tying it to the carrier information. Unlocked CDMA phones lack the carrier and user information and can work with any CDMA service provider, but the service provider must add the phone to its system and activate it remotely. The necessity of the activation process severely limits any advantages to an unlocked CDMA phone.


In addition to buying an unlocked cellphone, some users want to unlock a phone they already own to take advantage of the benefits of switching SIM cards. However, the legality of unlocking cellphones was unclear. In 2010, the Library of Congress Copyright Office, which interprets the Digital Millennium Copyright Act, extended a rule that excludes cellphone unlocking from acts that violate the DCMA. Essentially, this makes prosecution of cellphone unlocking impossible under the DCMA.

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