[McKee]

The five letter password is often butchered.. the "change on" thing is for if your password is compromised. Usually a password is changed every 24 hours but if the password is overheard by the enemy and the challenger knows / suspects this, he could open his challenge with (say password is PHONE) OSCAR OSCAR....... NOVEMBER NOVEMBER. Expected response should be ECHO ECHO. Many times the enemy will overhear PAPA PAPA and the response HOTEL HOTEL but he wont know the password in full, so this is effective. It doesn't necessarily need to be repeated twice but this is common practice.