In 1996,a completely new concept was introduced when the first Web TV set-top boxes came onto the market.
In 1996作时间状语,主语是a completely new concept.
was introduced系表结构。introduced作表语。
when引导的状语从句。
整句话翻译:1996年,一个全新的概念被引进,当第一台互联网电视机顶盒面世。
望采纳,谢谢。