My dad was a Fire Control Technician on a USN cruiser. I didn't learn until I was older that meant he handled radar and firing of guided missiles, he was not a fireman. When he retired he went into TV repair, which in those days meant replacing tubes and such. My first job with him was to carry a bag of tubes to the local drugstore once a week and use the tester they had by the front door. We fixed every set on the block, usually for a slice of pie.