414 is Milwaukee, WI or that general area. I live in Madison, my Mom lives here too on the other side of town, we both get calls from this number. They never leave a message, if I answer, the caller hangs up. If I try calling back, its a busy signal or it just rings forever.

This might be some sort of tracking service, trying to determine if people are home? If you answer, you're there and they know to start recording your devices.