For other meanings of the acronym PUC, see the disambiguation page PUC.

PUC is an abbreviation for the phrase personal unblocking code used in GSM mobile phones. Most mobile telephones offer the feature of personal identification number protection. After switching on the phone, the user is (optionally) requested for security reasons to enter a 4-8 digit PIN enabling the phone's non-emergency calling functions. If the wrong PIN is typed in more than three times, either the SIM card, the device or both become permanently locked.

They can be reverted to their original unlocked state, however, by entering a PUC, but if the wrong PUC is entered ten times in a row, the device will become permanently blocked and unrecoverable, requiring a new SIM card. Cellular phone users are therefore advised by most providers to keep their PUC written down in a safe place separate from the device.

PUC is also called PUK, the abbreviation for PIN unblocking key or personal unblocking key.

GSM Standard

PUK | PUK