They only had to note what zone (local, local long distance, or long distance) or what country you were connecting to and the duration of the call. The number y

They only had to note what zone (local, local long distance, or long distance) or what country you were connecting to and the duration of the call. The number you dialed was not recorded. So if you called Germany for 33 minutes they could charge you the correct international rate, but without the pen register they would have no idea what number you actually dialed. By the late 80s they were logging numbers electronically. This applies only before that time.