I cant remember. It is either by phone or a knock on the door. They usually wait when they knock until they hear a "thank you" or the phone is answered. I know the whole gang will break into your room and shake you awake!!!

Seriously I always carry a small alarm clock. I like to know what time it is if I wake up in the night. Mine has a little place on the top I push down and it lights up and I use it as a flash light when I need to make a necessary call to the ladies room during the night. Could not travel without that.