set-top
/ˈsɛt tɒp/adjective
Designating an object (usually an aerial or signal decoder) which is designed to be positioned on top of a television set. Frequently in set-top box noun Broadcasting a box-shaped signal decoder for viewing cable or satellite television or giving television access to the Internet, or one which converts a digital television signal to analogue for viewing on a conventional set.
Origin
1970s; earliest use found in B.S.I. News. From set + top.