Need to give password for the extensions without being noticed by third party

Hi guys, I'm new to pbx with limited technical knowledge , when I was searching for a way to give password for the outgoing calls I came accross with an option called pin set , where it worked pretty well for me but the only disadvantage is that when I call from the hard phone the password is clearly visible in the screen for the person who sits next to me which is not good. so, is there any other way to give password for all outgoing calls without being noticed by others , it would be of great help if you guys help me with this .