For GXP21xx/14xx, when pressing and holding the STAR * key for about 4 to 5 seconds, the keypad will lock. To unlock, press and hold the STAR * key 4 to 5 seconds, then a window to enter a password will appear and the following message "LEFT for backspace, MENU for ok". Enter the password (by default, there is no password. In this case, leave it blank), then press the MENU key (the round button in the center of the navigation keys). The keypad will now be unlocked.