It's a switch from SD (Standard Definition) analog to SD digital. And the set top box does the conversion from digital (that it receives) to analog (what the old TV needs).
I have a family friend that only has Ariel TV at his place. He has a big Ariel on the top of his house. He said that he is planning on getting a couple of the set top boxes for the switch over.
My question is, does he need to replace the Ariel with an HDTV model? or will his old Ariel with an HD capable one to work with the set top box????