Need more context. Also, there seems to be a mistake or missing final character after 域. Having that is critical. This might have something to do with a function that validates a response of some kind, but without some kind of context, I can only offer this vague guess. Hope this helps anyway.

Seems like a familiar expression in stereo magazines.

「有効」は｢有効な・・(正しい)｣という意味で｢無効な」= invalid に対応する言葉として「有効」= valid のほうが良いと思います。

「域」は｢領域」という意味で "area" と訳した方が良いと思います。

Sorry, there is no reference. This is all based on my experience.