If you have the passcode lock feature enabled, when entering an incorrect passcode, the iPhone will buzz and the screen area for the passcode entry turns red. You can then enter the correct passcode. If you enter the incorrect passcode several times in a row, you must wait a period of time to re-enter the passcode. If you have the erase data option enabled with your passcode lock, after 10 failed passcode attempts your iPhone will be completely erased.