LG G3100 User Manual page 162

You can use security code to avoid unauthorized use of your phone.
When you switch on your phone, your phone will request security
code always if you set phone lock to "On". If you set phone lock to
"Automatic", your phone will request security code only when you
change your SIM card.
When you enable Automatic key lock, keypad will be lock
automatically on an idle screen after 25 seconds without any key
requesting.
• If you want to lock your phone keypad manually, enter Top
menu and press * key.
• If you want to unlock your phone keypad, press < [unlock]
key and then press * key. But if you enabled Automatic
key lock before, your phone keypad will be unlock and then
after 25 seconds the keypad will be lock up again
automatically.
57