All subscriber related information transferred to the ME during operation must be deleted after the removal of the SIM or deactivation of the MS. Examples of such information are the PIN and the PUK codes.
PIN MANAGEMENT
A SIM is required to have a PIN function even if it is deactivated by a user. The PIN consists of 4 to 8 digits. An initial PIN is loaded by the network operator at subscription time. Afterwards the PIN, including the length, can be changed by the user. In addition, the user can decide whether to use the PIN function or not by activating an appropriate SIM-ME function called the PIN disabling function. The PIN is disabled until the user changes the status of the function. This PIN disabling function can be blocked at subscription time by a person authorized to do so. If an incorrect PIN is entered, the user is informed. After three consecutive incorrect entries the SIM is blocked, even if between attempts the SIM has been removed or the MS has been switched off.
BLOCKING/UNBLOCKING OF SIM
When a SIM is blocked GSM network operations are forbidden. To unblock the SIM, the user must enter the PIN Unblocking Key, PUK. The PUK is an 8 digit numerical code. If the PUK is entered incorrectly the user is informed. The user can make 10 attempts to enter the PUK before the system blocks entry, in which case the subscriber must contact their network operator.
so grateful, it helps me a lot. thanks so much
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