Each mobile phone has its own security code which is usually provided by the handset manufacturer for safety or privacy purposes. Generally speaking, this security code will always remain the default unless you changed it for your own convenience, so it can also be called factory set codes. So if performing a certain function in the security settings, the phone will ask for it to access the menu or other functions. It will also be required if you want to reset the phone to its original factory settings or to make any changes in the security settings.
But sometimes it might occur that you keep dialing the default security code for several times, it still fails to work and you will get a message of a wrong code inserted, this means the default code has been changed to some other code by its owner or the user or even someone else. If so, you might need to input the new one or seek help from other channels. It is therefore advisable that when setting up a new code, do make it easier to remember, because if you enter an incorrect security code five times in succession, the phone ignores further entries of the code, and you'll have to wait for five minutes and enter the code again!
So if you forget the default security code or never created one, refer to the following list for the corresponding codes of your brand of cell phone:
Samsung: 0000 / 00 00 00 / 00 00 00 00 (8 times zero)
All other brands of cell phones ( Sony, Motorola, LG, Panasonic, etc): 0000 / 1234 / 9999
Chinese brands: 1122 / 0000 / 1234
In the case that the default codes are still not working, you will have to reset them through special software which is different for different brands of cell phones or you can format the handsets through hard-reset methods
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