Typically, a locked handset will display a message if a restricted SIM is used, requesting the unlock code. On recent phone models running Android software, the phone will display a message saying “SIM network unlock PIN” or “Enter Network Lock Control Key” if network locked. Windows phones will display the message, “This SIM card can only be used on specific networks. Contact your customer service center for the unlock code”. Other handsets may display different messages such as "Enter special code" or "Enter unlocking code," or in some cases the handset will simply display a message stating that it is locked. Once a valid code is entered, the handset will display "Network unlocked” or “Network unlock successful”.