You can use the lock feature to prevent unauthorized people from making outside calls from your extension while you are away from the extension. The user of the first extension on the system can unlock extensions without needing to know the code used to lock the phone. They can do this using Feature 22.
To Lock Your Extension
2.Dial a four digit code using the 0 to 9 numbers .
3.Redial the four digit code.
To Unlock Your Extension
2.Dial the four digit code you used to lock the extension.