How do Hotel wake up call services work?

Is it run by a computer? It seems the hotel operator always seems to know what room your calling from, and he simply inputs the time you requested to be woken up at.

they have a switchboard so when you call the desk from your room, they know what room it is.

they call u

there are a few different methods. some hotels write your name and room number down on a list for someone to personally call you in the morning. some type it into a computer database and someone personally calls you. others have spent extra money on an automated system that automatically calls you based upon the time entered into their database.