They have some type of system worked out

Elliott has been waking up at 6:15 everyday. Berkley 7:15 has been the earliest. E stayed at my parents house last night, I was looking forward to sleeping in a bit today. Not only did Berkley wake up 4 times last night, she got up at 6:30. HOW do they do it? Is there a punch in system I'm not aware of? Did E put some type of alarm in B's room? I'm mystified.